⚙️ Drugs by Mechanism

Grouped by how the drug actually works — what it does at the receptor, enzyme, channel or pump. This one cuts across body systems on purpose: a beta blocker and an antipsychotic are both receptor blockers, and seeing that is the point. Same 959 drugs.

HA high-alert drug · BBW has a black box warning · click any drug to open its card.

Receptor blockers (antagonists)Receptor and signal activators (agonists)Enzyme inhibitorsIon channel modulatorsPump and transporter blockersClotting cascade agentsCell wall, membrane and entry agentsNucleic acid and protein synthesis interferenceImmune modulationReplacement, binding and metabolic agentsMixed & unclear mechanism
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Receptor blockers (antagonists) 143

Adrenergic receptor blockers (beta and alpha-1)20

Sit on adrenaline's receptors so the sympathetic signal cannot land. Beta-1 blockade in the heart slows rate and force; alpha-1 blockade relaxes vessel walls, the bladder neck and the prostate.

-olol takes the foot off the heart's gas pedal; -osin loosens the pipes, blood and urinary.

  • Beta-1 blockade means an apical pulse before every dose - hold for a rate under 60.
  • Nonselective beta blockers (propranolol, nadolol, sotalol) also hit beta-2 - ask about asthma and COPD.
  • Alpha-1 blockade causes first-dose syncope and orthostasis - dose at bedtime and rise slowly.
  • Never stop a beta blocker abruptly; upregulated receptors rebound into tachycardia and angina.
Angiotensin II and aldosterone receptor blockers16

The hormones are still made, but their receptors are plugged. Blocking AT1 keeps vessels dilated; blocking the aldosterone receptor in the distal nephron dumps sodium and water while holding potassium back.

-sartan locks angiotensin out of the door; spironolactone locks aldosterone out and keeps the K+.

  • Blocking the receptor instead of the enzyme leaves bradykinin alone - so no ACE cough.
  • Both ends of this pathway retain potassium; monitor K+ and keep salt substitutes away.
  • ARBs cause fetal renal injury - stop the moment pregnancy is suspected.
  • Spironolactone also blocks androgen receptors, so gynecomastia and menstrual changes are expected, not rare.
Muscarinic (anticholinergic) blockers15

Block acetylcholine at muscarinic receptors, so the parasympathetic 'rest and digest' signal is cut off. Secretions dry up, heart rate rises, gut and bladder muscle relax, and pupils dilate.

Can't see, can't pee, can't spit, can't poop - and hot as a hare.

  • Every effect follows from drying and relaxing: dry mouth, blurred vision, constipation, urinary retention.
  • Contraindicated in narrow-angle glaucoma - pupil dilation blocks aqueous outflow.
  • No sweating means no cooling; warn about heat stroke in hot weather.
  • Inhaled forms (ipratropium, tiotropium) stay mostly in the airway, so systemic effects are milder.
Histamine receptor blockers (H1 and H2)17

Occupy histamine's receptor so histamine cannot trigger it. H1 blockade in skin and vessels stops itch, hives and swelling; H2 blockade on the stomach's parietal cell turns acid production down.

H1 is skin and nose, H2 is stomach - and first-generation H1 drugs cross into the brain and knock you out.

  • H1 blockade stops itch and swelling but not bronchospasm - it is never the rescue drug in anaphylaxis.
  • First-generation agents also block muscarinic receptors: sedation, dry mouth, retention, confusion in elders.
  • Second-generation agents barely cross into the brain, so far less sedation.
  • H2 blockers (-tidine) are best at bedtime for the nighttime acid surge; raising gastric pH alters absorption of other drugs.
Dopamine D2 / serotonin receptor blockers (antipsychotics)23

Block dopamine D2 receptors in the brain's limbic pathway, turning down the dopamine overactivity behind hallucinations and delusions. Second-generation agents also block 5-HT2A, which softens the motor side effects.

Block dopamine everywhere it goes: mood improves, movement suffers, prolactin rises.

  • Blocking D2 in the motor pathway causes EPS - watch for stiffness, tremor, restlessness and late-onset tardive dyskinesia.
  • D2 blockade in the pituitary lifts prolactin: breast tenderness, galactorrhea, missed periods.
  • Rigidity plus fever plus altered mental status is neuroleptic malignant syndrome - stop the drug and cool the patient.
  • Atypicals block many receptors at once, so expect weight gain, high glucose and lipids; clozapine also needs ANC monitoring.
Peptide and lipid mediator receptor blockers13

Block the receptors for the body's own signalling molecules - CGRP, leukotrienes, endothelin, vasopressin. The mediator is still released; it simply has nowhere to land.

-gepant blocks migraine's CGRP, -lukast locks out leukotrienes, -sentan opens the lung, -vaptan wastes water.

  • CGRP blockers do not constrict vessels, so unlike triptans they are safe in coronary disease; constipation is the usual complaint.
  • Leukotriene blockers are controllers only - never for an acute asthma attack - and carry a neuropsychiatric boxed warning.
  • Endothelin blockers are potent teratogens with liver toxicity: monthly pregnancy tests and LFTs.
  • Vaptans cause a WATER diuresis, so sodium climbs - recheck Na+ often and correct slowly.
Serotonin 5-HT3, neurokinin, orexin and glutamate blockers15

Plug a CNS receptor that drives one specific unwanted signal: 5-HT3 on the vagus and vomiting center, NK1 for delayed vomiting, orexin for wakefulness, NMDA and AMPA for runaway excitation.

-setron cuts the vomit wire; -pitant kills the second-day nausea; -orexant switches the wake signal off.

  • 5-HT3 blockers go in BEFORE chemo or anesthesia - they block the signal, they do not rescue active vomiting; they also prolong QT.
  • NK1 blockers cover the DELAYED phase of chemo nausea; pair them with a 5-HT3 blocker for day one.
  • Memantine blocks NMDA to slow excitotoxic damage - it protects neurons, it does not restore memory.
  • Orexin blockers cause sleep without GABA - less hangover, but sleep paralysis and vivid dreams happen.
Sex-hormone receptor blockers and GnRH axis agents15

Cut the sex-hormone signal in one of two places. Receptor blockers sit on the estrogen or androgen receptor so the hormone cannot switch growth genes on; GnRH agents work upstream at the pituitary so the gonads are never told to make the hormone at all.

Block the seat, or cut the phone line to the factory.

  • Tamoxifen blocks estrogen in breast tissue but stimulates it in the uterus - report any new vaginal bleeding, and know the clot risk.
  • GnRH AGONISTS cause a hormone flare for 1-2 weeks first - warn about worse bone pain or urinary symptoms; antagonists have no flare.
  • Androgen blockade brings hot flashes, fatigue, falls and (apalutamide, enzalutamide) seizures.
  • Months of hormone deprivation means bone loss - expect DEXA scans plus calcium and vitamin D.
Neuromuscular (nicotinic) blockers4

Act at the nicotinic receptor of the neuromuscular junction. Nondepolarizers plug the receptor so acetylcholine cannot act; succinylcholine over-activates it and leaves the membrane stuck depolarized.

Paralysis only - the patient feels and hears everything unless you sedate them.

  • No analgesia, no sedation, no amnesia - always pair with a sedative and an analgesic.
  • Airway and ventilator must be ready before the dose; the diaphragm is paralyzed too.
  • Succinylcholine's depolarization dumps potassium out of cells - avoid in burns, crush injury and paralysis.
  • Nondepolarizers are reversed with an anticholinesterase or, for rocuronium/vecuronium, sugammadex.
Opioid receptor antagonists5

Compete with opioids at the mu receptor and win, knocking the opioid off. Central antagonists reverse sedation and respiratory depression; peripheral ones only free up the gut.

Naloxone kicks the opioid off the receptor - fast, and the patient wakes up angry.

  • Naloxone works in minutes but wears off before most opioids do - keep monitoring and expect to redose.
  • Reversal precipitates instant withdrawal: pain, agitation, vomiting, hypertension.
  • Peripheral blockers (methylnaltrexone, naloxegol, alvimopan) treat opioid constipation without undoing analgesia.
  • Naltrexone maintenance blocks the receptor for a day or more - any opioid given for real pain will not work.

Receptor and signal activators (agonists) 137

Beta-2 receptor agonists (bronchodilators)10

Switch on beta-2 receptors on bronchial smooth muscle, which relaxes the airway and widens it within minutes. The same receptors in skeletal muscle and the heart explain the shakes and the racing pulse.

-terol: opens the tubes and revs the motor.

  • Short-acting (albuterol) is the RESCUE inhaler; long-acting (-terol with an 'l' partner) is never used alone in asthma.
  • Tremor, tachycardia and jitteriness are beta stimulation, not an allergy - reassure and reassess technique.
  • Beta-2 stimulation drives potassium INTO cells - watch for hypokalemia with heavy use.
  • Bronchodilator first, then the steroid inhaler, so the steroid reaches open airways.
Adrenergic receptor agonists (catecholamines and alpha/beta agents)8

Directly stimulate alpha and beta receptors the way the body's own adrenaline does. Alpha-1 squeezes vessels and raises pressure; beta-1 raises heart rate and force; beta-2 opens airways.

Fight-or-flight in a syringe - the receptor MIX decides the effect. Not all of them are catecholamines: phenylephrine and midodrine are not.

  • Alpha-1 vasoconstriction means tissue death if it extravasates - central line preferred, phentolamine is the antidote.
  • Titrate to MAP and rhythm, not to the drip rate; beta-1 stimulation buys pressure at the cost of oxygen demand.
  • Epinephrine is the anaphylaxis drug because it does all three: opens airway, squeezes vessels, supports the heart.
  • Continuous cardiac and blood pressure monitoring is mandatory on any drip.
  • Pure alpha-1 agents (phenylephrine, midodrine) squeeze vessels with no direct push on the heart, so the pulse reflexively SLOWS as the pressure rises - that reflex bradycardia is the giveaway.
Central alpha-2 agonists5

Stimulate alpha-2 receptors in the brainstem, which act as a brake on sympathetic outflow. Less norepinephrine leaves the CNS, so heart rate, vessel tone and blood pressure all fall.

An adrenergic drug that CALMS - alpha-2 is the off switch, not the on switch.

  • Sedation and dry mouth are the mechanism working centrally, not a reaction.
  • Abrupt withdrawal causes rebound hypertensive crisis - taper, and never let a patch fall off unnoticed.
  • Orthostatic hypotension and bradycardia: sit before standing, hold for low pulse.
  • Tizanidine uses the same brake on spinal motor neurons to relieve spasticity.
Dopamine agonists and precursors7

Restore dopamine signalling in the striatum. Agonists stimulate the dopamine receptor directly, bypassing the dying neurons; levodopa instead supplies the raw material the surviving neurons convert into dopamine.

Levodopa refills the tank; the -ole agonists skip the tank and press the pedal.

  • Dopamine stimulation causes nausea, orthostatic hypotension and vivid hallucinations, especially in elders.
  • Sudden sleep attacks and impulse-control problems (gambling, shopping, hypersexuality) come with the territory - ask directly.
  • Never stop abruptly; a parkinsonism-hyperpyrexia syndrome can follow.
  • Levodopa competes with dietary protein for absorption, and carbidopa is there only to stop it being converted before it reaches the brain.
Opioid receptor agonists20

Bind mu opioid receptors in the spinal cord and brain, closing the gate on pain signals and changing how pain feels. The same receptors in the brainstem and gut slow breathing and slow the bowel.

Mu = miosis, morphine, muted breathing, motionless gut.

  • Respiratory depression is the killer - count a full minute of respirations and hold under 12.
  • Pinpoint pupils plus sedation plus slow breathing is the overdose triad; naloxone reverses it at the same receptor.
  • The gut receptors never develop tolerance, so start a bowel program on day one.
  • Peripheral-only agents (loperamide, difenoxin) stay in the gut and stop diarrhea without analgesia.
Serotonin 5-HT1 agonists (triptans and ergots)10

Stimulate 5-HT1B receptors on dilated meningeal vessels so they constrict, and 5-HT1D receptors on trigeminal nerve endings so they stop releasing inflammatory peptides.

-triptan: tightens the throbbing vessel and quiets the nerve.

  • It constricts vessels everywhere - contraindicated in coronary artery disease, uncontrolled hypertension and stroke history.
  • Chest, jaw or throat tightness is the vasoconstriction; assess it, do not dismiss it.
  • Abortive, not preventive - take it at the first sign of the migraine, and cap doses to avoid rebound headache.
  • Never within 24 hours of an ergot, and watch for serotonin syndrome with SSRIs and SNRIs.
GABA-A receptor positive modulators22

Sit at a side pocket of the GABA-A chloride channel and make the brain's own GABA far more effective. Chloride pours in, the neuron is harder to fire, and the whole CNS is turned down.

Does not open the door itself - it holds the door open longer for GABA.

  • CNS depression is dose-dependent and additive - alcohol and opioids together are the classic fatal combination.
  • Because it needs the body's own GABA, the ceiling is higher than a barbiturate's - flumazenil reverses it.
  • Fall risk and next-day grogginess in older adults; these are on the Beers list.
  • Physical dependence is real - abrupt withdrawal causes tremor, delirium and seizures, so taper.
Incretin pathway agents (GLP-1 agonists and DPP-4 inhibitors)13

Two ways to work the same gut hormone: the -tides stimulate the GLP-1 receptor directly, while the -gliptins block DPP-4, the enzyme that chews GLP-1 up, so the body's own hormone lasts longer. Either way insulin is released only when glucose is high and glucagon is suppressed.

-glutide pushes the button, -gliptin stops the body from taking the finger off it.

  • Release is glucose-dependent, so hypoglycemia is unlikely alone - it appears when stacked with insulin or a sulfonylurea.
  • GLP-1 agonists slow gastric emptying: nausea, fullness, vomiting, and altered absorption of other oral drugs.
  • Boxed warning for thyroid C-cell tumors with the agonists - screen for MEN2 and medullary thyroid cancer.
  • Both classes are linked to pancreatitis; severe persistent abdominal pain radiating to the back means stop and call.
Prostaglandin and prostacyclin receptor agonists10

Supply or mimic prostaglandins at their own receptors. Depending on the receptor they open the eye's uveoscleral drain, dilate pulmonary arteries, protect gastric mucosa, or ripen the cervix and contract the uterus.

-prost-: prostaglandin in the name, and it always relaxes or opens something.

  • Eye drops darken the iris, eyelid skin and lashes and can be permanent - warn before the first bottle.
  • Pulmonary prostacyclins are potent vasodilators: headache, flushing, jaw pain, and never interrupt an infusion.
  • Misoprostol protects the stomach from NSAIDs but causes uterine contraction - pregnancy is an absolute contraindication.
Nitrates and direct vasodilators6

Deliver nitric oxide - or act like it - inside vascular smooth muscle, raising cyclic GMP so the vessel wall relaxes. Veins dilate first, which drops preload and the heart's oxygen demand; arteries follow at higher doses.

Nitric oxide is the body's own 'relax' molecule; nitrates hand it over directly.

  • Headache and flushing mean it is working - and mean the pressure is dropping; sit the patient down.
  • Absolutely no PDE-5 inhibitor within 24-48 hours - the combined vasodilation causes irreversible hypotension.
  • Tolerance develops fast, so build in a nitrate-free interval of 8-12 hours each day.
  • Nitroprusside breaks down to cyanide with prolonged high-dose use - protect from light and watch for acidosis.
Other receptor agonists and modulators26

A mixed set that all work by switching a specific receptor ON - acetylcholine, vasopressin, thrombopoietin, calcium-sensing, melatonin, GABA-B, PPAR-alpha, 5-HT4, guanylate cyclase-C, beta-3 and sphingosine-1-phosphate.

Different receptors, same trick - press the button the body normally presses.

  • Cholinergic agonists are the mirror image of anticholinergics: SLUDGE, bradycardia and wheezing - atropine is the antidote.
  • Vasopressin agonists insert water channels in the kidney: water comes back without salt, so watch for dilutional hyponatremia.
  • Thrombopoietin agonists tell the marrow to build platelets over days to weeks - not a rescue for active bleeding.
  • Gut agonists (linaclotide, plecanatide, prucalopride) pull fluid in or speed transit - diarrhea is the dose-limiting effect.

Enzyme inhibitors 197

ACE inhibitors15

Block the enzyme that converts angiotensin I into angiotensin II, so the body simply cannot make its strongest vasoconstrictor. The same enzyme normally destroys bradykinin, which now builds up.

-pril: no angiotensin II means no squeeze - and the leftover bradykinin gives the dry cough.

  • The dry hacking cough is bradykinin, not a cold - switch to an ARB if it is intolerable.
  • Angioedema of lips, tongue or throat is the same mechanism and is an airway emergency.
  • Less aldosterone means potassium is retained - check K+ and avoid salt substitutes.
  • Boxed warning in pregnancy; also check creatinine, since angiotensin II maintains glomerular pressure.
HMG-CoA reductase inhibitors (statins)8

Block HMG-CoA reductase, the rate-limiting enzyme of cholesterol production in the liver. The liver, short on cholesterol, pulls more LDL out of the blood by making extra LDL receptors.

-statin: shuts down the liver's cholesterol factory line.

  • Most cholesterol is made overnight, so short-acting statins are dosed in the evening.
  • The pathway also makes CoQ10, which is why muscle aches happen - new muscle pain plus dark urine means check a CK for rhabdomyolysis.
  • Grapefruit juice blocks the enzyme that clears several statins - levels climb and so does muscle risk.
  • Baseline and periodic LFTs; the drug works in the liver, so that is where toxicity shows.
COX inhibitors (NSAIDs, aspirin, acetaminophen)13

Block cyclooxygenase, the enzyme that turns arachidonic acid into prostaglandins. Less prostaglandin means less pain, fever and inflammation - but also less protection for the stomach lining and less blood flow to the kidney.

No prostaglandin, no pain - and no stomach lining either.

  • Losing the stomach's protective prostaglandins is why GI bleeding happens - give with food and watch for black stools.
  • Prostaglandins keep the afferent arteriole open; in dehydration or heart failure this is how NSAIDs cause acute kidney injury.
  • Aspirin blocks COX-1 in platelets irreversibly for their whole 7-10 day life - stop it before surgery.
  • Celecoxib spares COX-1 so the stomach is safer, but the cardiovascular clot risk is higher.
Phosphodiesterase inhibitors12

Block the enzyme that destroys cyclic AMP and cyclic GMP, so those second messengers pile up inside the cell. Smooth muscle relaxes, the heart contracts harder, and inflammatory cells quiet down - which one happens depends on the PDE subtype.

Stops the cleanup crew, so the 'relax' signal keeps shouting.

  • PDE-5 in the penis and lung: never within 24-48 hours of any nitrate - the combined vasodilation causes fatal hypotension.
  • Sudden vision or hearing loss with PDE-5 drugs must be reported immediately.
  • PDE-3 inhibitors (milrinone) raise contractility and dilate vessels - watch pressure and rhythm on the drip.
  • PDE-4 inhibitors (roflumilast, apremilast) cause weight loss, diarrhea and mood changes - weigh weekly and ask about depression.
Neurotransmitter-degrading enzyme inhibitors13

Block the enzymes that break a neurotransmitter down, so more of it stays in the synapse. Cholinesterase inhibitors preserve acetylcholine; MAO-B and COMT inhibitors preserve dopamine.

Do not make more - just stop the shredder.

  • More acetylcholine means SLUDGE: salivation, tearing, urination, diarrhea, GI cramps, bradycardia - atropine is the antidote.
  • Cholinesterase inhibitors for Alzheimer's slow decline; give with food and expect nausea and vivid dreams early.
  • MAO-B inhibitors lose their selectivity at high dose - watch for tyramine reactions and serotonin syndrome with SSRIs and meperidine.
  • COMT inhibitors are only useful WITH levodopa; harmless orange urine, but tolcapone needs liver monitoring.
Protein kinase inhibitors47

Sit in the ATP pocket of a signalling kinase - the enzyme a cancer or immune cell uses to relay 'grow and divide' or 'inflame'. With the relay switch jammed the growth or inflammation signal never reaches the nucleus.

-nib: it NIBbles the growth signal. -citinib: JAK is the inflammation relay.

  • These are targeted, not classic chemo - the marrow is hit less, but rash, diarrhea and fatigue are near universal.
  • Many prolong QT and raise blood pressure; get a baseline ECG and check BP at every visit.
  • Hepatotoxicity is common across the class - monitor LFTs and report jaundice or right upper quadrant pain.
  • JAK inhibitors block immune signalling, so they carry boxed warnings for serious infection, TB reactivation, clots and malignancy - screen before starting.
Viral protease, integrase, polymerase and entry blockers28

Disable a step the virus cannot skip: the protease that cuts new proteins to size, the integrase that staples viral DNA into ours, the polymerase and neuraminidase that copy and release new virions, or the envelope proteins it uses to get in at all.

-navir cuts nothing, -gravir staples nothing, -tamivir escapes nothing.

  • Protease inhibitors are powerful CYP3A4 blockers - screen every other drug, herb and statin for interaction.
  • Ritonavir is often there only to 'boost' by blocking metabolism, not to treat.
  • Protease inhibitors cause fat redistribution, insulin resistance and high lipids - monitor glucose and lipid panels.
  • Neuraminidase inhibitors only help if started within 48 hours of symptom onset; entry blockers need tropism testing first.
Reverse transcriptase inhibitors (NRTIs and NNRTIs)16

Stop HIV's reverse transcriptase from copying viral RNA into DNA. Nucleoside analogs get built into the growing chain and end it; non-nucleosides bend the enzyme out of shape.

Reverse transcriptase is the virus's photocopier - the NRTI is a jammed sheet of paper.

  • Nucleoside analogs poison mitochondria too: lactic acidosis with an enlarged fatty liver is the emergency to know.
  • Abacavir hypersensitivity is HLA-B*5701 linked - test before the first dose and never rechallenge.
  • Tenofovir is hard on kidneys and bone - watch creatinine, phosphate and bone density.
  • Adherence is the whole game; missed doses let the enzyme mutate into resistance.
Bacterial DNA and RNA enzyme inhibitors13

Attack enzymes bacteria need to handle their own genetic material - DNA gyrase and topoisomerase IV for the quinolones, DNA-dependent RNA polymerase for the rifamycins. The bacterial chromosome cannot be unwound or transcribed.

-floxacin unwinds nothing; rif- turns everything orange.

  • Fluoroquinolones carry boxed warnings for tendon rupture, peripheral neuropathy and CNS effects - stop at the first tendon pain.
  • Cations bind quinolones in the gut: separate antacids, calcium, iron and dairy by 2-6 hours.
  • Rifampin turns urine, sweat and tears orange and permanently stains soft contact lenses - warn first.
  • Rifampin is a powerful CYP inducer, so contraceptives, warfarin and antiretrovirals all lose potency.
Hormone and metabolic enzyme inhibitors21

Block the enzyme that MAKES a substance rather than the receptor it acts on - the aromatase that builds estrogen, the 5-alpha-reductase that builds DHT, xanthine oxidase that builds uric acid, carbonic anhydrase, lipase, and the gut enzymes that release glucose.

Do not block the hormone - shut down the factory that makes it.

  • Aromatase inhibitors take estrogen to near zero, so joint pain, hot flashes and bone loss follow - DEXA, calcium and vitamin D.
  • 5-alpha-reductase inhibitors take 6 months to shrink the prostate and drop PSA by about half - never handled by pregnant staff.
  • Xanthine oxidase inhibitors prevent gout, they do not treat the attack - and starting one can trigger a flare.
  • Carbonic anhydrase inhibitors dump bicarbonate: expect metabolic acidosis, tingling and a sulfa cross-reaction risk.
PARP, proteasome and other targeted pathway inhibitors11

Block the machinery a cancer cell uses to survive its own damage: PARP that patches broken DNA, the proteasome that clears worn-out proteins, and the histone enzymes and export proteins that control which genes get read.

The cell can still break - it just cannot fix or tidy up afterwards.

  • PARP inhibitors work best where DNA repair is already broken (BRCA) - expect anemia, fatigue and low counts.
  • Proteasome inhibitors cause painful peripheral neuropathy - screen for numbness and tingling at every visit.
  • Bortezomib is fatal if given intrathecally; it is subcutaneous or IV only.
  • Tumor lysis syndrome can follow rapid cell kill - hydrate and watch potassium, phosphate and uric acid.

Ion channel modulators 48

Calcium channel blockers9

Plug the L-type calcium channel so calcium cannot enter the cell. In vessel walls that means relaxation and lower pressure; in the heart's conduction tissue it means a slower rate and weaker contraction.

-dipine relaxes the PIPES; verapamil and diltiazem slow the PUMP.

  • Dihydropyridines act on vessels: expect headache, flushing, reflex tachycardia and ankle edema.
  • Verapamil and diltiazem slow the AV node, so check apical pulse and never stack them with a beta blocker casually.
  • Less calcium in gut smooth muscle means constipation - verapamil is the worst offender.
  • Grapefruit juice raises levels of several of these; teach patients to avoid it.
Cardiac sodium and potassium channel blockers10

Change the shape of the cardiac action potential by blocking a specific channel. Sodium blockers slow how fast the impulse travels; potassium blockers lengthen repolarization so the cell cannot refire too soon.

Sodium slows the upstroke; potassium stretches the reset - and stretching the reset stretches the QT.

  • Anything that prolongs repolarization prolongs the QT - watch for torsades and keep potassium and magnesium replete.
  • These drugs are also proarrhythmic; continuous telemetry when starting or loading.
  • Amiodarone deposits everywhere over time: thyroid, lung, liver, cornea, skin - baseline TSH, LFTs, PFTs and eye exams.
  • Adenosine causes a few seconds of asystole on purpose - warn the patient, push fast, flush immediately.
Sodium channel blocking anticonvulsants11

Hold voltage-gated sodium channels in their inactive state, so a neuron that is already firing too fast cannot keep firing. Normal traffic gets through; a seizure's runaway train does not.

Use-dependent: the busier the neuron, the harder the drug clamps it.

  • Never stop abruptly - removing the clamp causes rebound status epilepticus.
  • Phenytoin has a narrow therapeutic window (about 10-20 mcg/mL) with zero-order kinetics: a small dose rise can be toxic; nystagmus and ataxia are early signs.
  • Rash on lamotrigine or carbamazepine can become Stevens-Johnson - stop and call for ANY new rash.
  • Carbamazepine induces its own metabolism and many others, and drops sodium; valproate is hepatotoxic and highly teratogenic.
K-ATP channel closers (sulfonylureas and glinides)4

Shut the ATP-sensitive potassium channel on the pancreatic beta cell. The cell depolarizes, calcium rushes in, and stored insulin is squeezed out whether or not glucose is actually high.

Close the K+ door, force the insulin out - glucose has no say in it.

  • Insulin release is NOT glucose-dependent, so hypoglycemia is the signature risk - never skip a meal after a dose.
  • Take with the first bite of the meal; glinides are so short-acting that a skipped meal means a skipped dose.
  • They need working beta cells - useless in type 1 diabetes.
  • Sulfonylureas are sulfa-based, cause weight gain, and cause a disulfiram-like reaction with alcohol.
Other ion channel modulators14

Everything else that works by changing what an ion channel does: calcium channel subunit binders in nerve terminals, epithelial sodium channel blockers in the nephron, chloride channel openers in the gut, and the funny-current and late-sodium channels in the heart.

Find the channel, find the effect - the ion that moves tells you the side effect.

  • Gabapentin and pregabalin damp calcium entry at nerve terminals - sedation, dizziness and falls, and taper to stop.
  • Amiloride and triamterene block the sodium channel aldosterone opens, so potassium is retained - hyperkalemia, not hypokalemia.
  • Ivabradine slows only the sinus node's funny current: it lowers rate without lowering contractility; visual brightness is a known effect.
  • Dantrolene blocks calcium release from the sarcoplasmic reticulum - it is the malignant hyperthermia drug.

Pump and transporter blockers 61

Proton pump inhibitors7

Bind the H+/K+ ATPase - the final pump that physically pushes acid into the stomach - and disable it permanently. That pump is done; acid output only returns as new pumps are built.

-prazole: not turning acid down, unplugging the pump entirely.

  • Give 30-60 minutes BEFORE a meal so the drug is present when the pumps switch on.
  • It is irreversible, so full effect takes a few days and outlasts the dose - do not expect instant relief.
  • Long term, low acid means poor absorption of B12, iron, calcium and magnesium - fracture risk and hypomagnesemia.
  • Low stomach acid also lets C. difficile and pneumonia in; use the shortest course that works.
Serotonin and norepinephrine reuptake blockers22

Block the transporter that vacuums serotonin or norepinephrine back into the presynaptic neuron. The neurotransmitter stays in the synapse longer, and over weeks the receptors adapt - which is why the mood effect is delayed.

The vacuum cleaner is unplugged, so the serotonin stays on the floor.

  • Two to six weeks for mood; energy returns first, which is exactly when suicide risk peaks - assess often.
  • Too much serotonin at once is serotonin syndrome: fever, agitation, tremor, hyperreflexia, clonus - stop and treat.
  • Never stop abruptly; the transporter rebounds into dizziness, flu-like aches and electric-shock sensations.
  • TCAs also block muscarinic, alpha-1 and cardiac sodium channels, which is why overdose is lethal - widened QRS on ECG.
Dopamine and norepinephrine reuptake blockers (stimulants)10

Block - and in the amphetamines, reverse - the dopamine and norepinephrine transporters, so those transmitters flood the synapse. Alertness, focus, heart rate and blood pressure all rise together.

Same transporter trick as an antidepressant, but on dopamine - so it works in an hour, not a month.

  • Sympathetic flood means check BP and pulse at every visit and avoid in uncontrolled hypertension or arrhythmia.
  • Appetite suppression and insomnia are the mechanism - give the last dose before mid-afternoon and monitor growth in children.
  • Schedule II with real abuse and dependence potential; count pills and watch for dose escalation.
  • Bupropion blocks the same transporters without serotonin, which is why it lowers the seizure threshold and does not cause sexual side effects.
SGLT2 inhibitors7

Block the sodium-glucose cotransporter in the proximal tubule, so glucose that was filtered is not reabsorbed. Sugar leaves in the urine, taking water and sodium with it.

-gliflozin: makes the kidney pee out the sugar.

  • Sugar in the urine feeds yeast and bacteria - expect genital mycotic infections and teach perineal hygiene.
  • It is an osmotic diuretic in effect: volume depletion, dizziness and falls, so watch pressure and hydration.
  • Euglycemic DKA is the trap - ketones can be high while glucose looks normal; check ketones for nausea and abdominal pain.
  • It needs working kidneys to work at all; effectiveness falls as GFR falls.
Loop and thiazide diuretics (sodium transporter blockers)6

Block a specific sodium transporter in the nephron so that sodium - and the water that follows it - is not reabsorbed. Loops hit the Na-K-2Cl carrier in the thick ascending limb; thiazides hit the Na-Cl carrier in the distal tubule.

Loops blast (the powerful one), thiazides trickle - and both wash potassium out the door.

  • Losing the K+ recycling in the loop means hypokalemia - monitor K+, teach potassium foods, and be extra careful with digoxin.
  • Dose in the morning so the diuresis does not ruin sleep, and weigh daily - 1 kg is about 1 L.
  • Loops are ototoxic when pushed fast IV; give slowly and watch for tinnitus and hearing change.
  • Both are sulfa-derived and both raise glucose, uric acid and calcium loss patterns - thiazides actually RETAIN calcium.
Other pump and transporter blockers9

Block a specific carrier so a substance cannot be moved where it usually goes: the sodium-potassium pump in the heart, urate and bile-acid carriers in kidney and gut, cholesterol uptake in the intestine, and the vesicle transporter that loads dopamine.

Every one of these stops a shuttle bus - find the cargo and you have the effect.

  • Digoxin blocks the Na/K pump, so calcium builds and contraction strengthens while rate slows - apical pulse, hold under 60, level 0.5-2 ng/mL.
  • Low potassium makes digoxin toxicity far more likely; nausea, visual halos and confusion are classic signs.
  • Probenecid blocks urate reabsorption - push fluids to prevent stones, and never start it during an acute gout attack.
  • VMAT2 blockers empty dopamine vesicles for tardive dyskinesia and chorea; watch for depression, parkinsonism and QT changes.

Clotting cascade agents 21

Factor Xa and thrombin inhibitors (direct, and the heparins)10

Block a single clotting factor in the middle of the cascade. The -xabans sit on factor Xa; the -atrans and -rudins block thrombin itself; the heparins work indirectly by supercharging antithrombin.

-Xa-ban tells you the target out loud: BAN factor Xa. The -xabans, -atrans and -rudins hit the factor DIRECTLY; the heparins do it INDIRECTLY, through antithrombin.

  • Bleeding is the effect taken too far - watch for bruising, black stools, headache, and hold before procedures.
  • Heparin needs aPTT monitoring and can cause HIT: a falling platelet count with new clotting, not bleeding.
  • LMWH and the oral agents need little monitoring but depend on kidney clearance - check creatinine.
  • Know the reversal: protamine for heparin, idarucizumab for dabigatran, andexanet for the -xabans.
Vitamin K antagonists (warfarin)1

Block the enzyme that recycles vitamin K, so the liver cannot finish building factors II, VII, IX and X. Existing factors keep working until they expire, which is why the effect takes days.

1972 - factors 10, 9, 7, 2 are the ones that need vitamin K.

  • Monitor INR; target is usually 2-3, and it takes 3-5 days for a dose change to show.
  • Vitamin K is the antidote - which means CONSISTENT green vegetables, not zero, or the INR swings.
  • Bridge with heparin at the start; protein C falls first and can transiently increase clotting.
  • Enormous interaction list (antibiotics, amiodarone, NSAIDs, alcohol, herbals) - recheck INR after any change.
Antiplatelet receptor blockers7

Stop platelets sticking to each other. The -grels block the ADP (P2Y12) receptor that activates the platelet; the IIb/IIIa blockers cover the final receptor that fibrinogen uses to bridge platelets together.

ADP blockers stop the invitation; IIb/IIIa blockers cut the handshake itself.

  • Effect lasts the platelet's lifespan for clopidogrel and prasugrel - stop 5-7 days before surgery.
  • Clopidogrel is a prodrug needing CYP2C19; poor metabolizers and PPIs like omeprazole blunt it.
  • Bleeding plus a low platelet count on a IIb/IIIa infusion means stop and check counts immediately.
  • Dual antiplatelet therapy after a stent is not optional - stopping early causes stent thrombosis.
Fibrinolytics (clot busters)3

Convert plasminogen into plasmin, the enzyme that digests fibrin. Unlike every anticoagulant, these dissolve a clot that already exists.

-plase: it PLAYS the clot apart. Anticoagulants prevent; only these destroy.

  • Time is everything - the drug only helps inside a narrow window from symptom onset.
  • It dissolves ALL clots, including protective ones: screen hard for recent surgery, bleeding, stroke and uncontrolled hypertension.
  • No IM injections, minimal sticks, hold pressure long, and monitor neuro status for intracranial bleeding.
  • Keep the patient on strict bedrest with continuous monitoring during and after the infusion.

Cell wall, membrane and entry agents 58

Beta-lactam antibiotics18

The beta-lactam ring binds the penicillin-binding proteins that cross-link peptidoglycan. Without cross-links the wall cannot be finished, and internal pressure bursts the bacterium.

The wall gets built with no mortar - the cell pops.

  • They only kill growing bacteria, so timing matters: give doses evenly around the clock.
  • Cross-allergy: ask about penicillin reaction before any cephalosporin, and know true anaphylaxis from a rash.
  • Beta-lactamase inhibitors (clavulanate, tazobactam, sulbactam) protect the ring - that is why the combination works when the plain drug fails.
  • Human cells have no cell wall, which is why these are so well tolerated - GI upset and yeast overgrowth are the usual complaints.
Glycopeptides and lipopeptides5

Bind the building block of the wall itself rather than the enzyme, so the bricks can never be laid. Daptomycin goes further and punches holes in the membrane, letting potassium leak out.

Not blocking the bricklayer - grabbing the brick.

  • Vancomycin infused too fast releases histamine: flushing of the face and torso, 'red man' - slow the rate, do not call it an allergy.
  • Nephrotoxic and ototoxic; monitor trough or AUC levels and creatinine.
  • These are big molecules that cannot cross the gut, so oral vancomycin stays in the bowel - which is exactly why it treats C. difficile.
  • Daptomycin damages skeletal muscle - check a baseline CK and repeat weekly, and hold statins.
Antifungals that attack the fungal membrane and wall19

Fungal membranes use ergosterol where ours use cholesterol. Azoles and allylamines block the enzymes that build ergosterol, polyenes bind it and tear pores in the membrane, and echinocandins block the glucan wall instead.

Ergosterol is the fungus's cholesterol - break it and the membrane leaks.

  • Azoles are strong CYP inhibitors and are hepatotoxic - screen every co-medication and monitor LFTs.
  • IV amphotericin B is 'shake and bake': fevers, rigors and severe nephrotoxicity - premedicate, hydrate with saline, follow K+ and Mg2+.
  • Echinocandins target a wall humans do not have, so they are the best tolerated - IV only.
  • Because human cells share sterol chemistry, systemic antifungals are far more toxic than antibacterials - always check renal and liver function.
Antimycobacterial, antimalarial and antiparasitic agents16

Attack a structure or pathway only the organism has. TB drugs block the waxy mycolic acid wall or the organism's ATP supply; antimalarials poison the parasite's ability to detoxify heme; topical scabicides paralyze the arthropod's own nerve channels.

RIPE for TB - Rifampin, Isoniazid, Pyrazinamide, Ethambutol; and the antimalarials poison what the parasite eats.

  • Isoniazid burns through vitamin B6 - give pyridoxine to prevent neuropathy; INH and pyrazinamide are hepatotoxic, so no alcohol and monthly LFTs.
  • Ethambutol damages the optic nerve: baseline and monthly color vision and acuity checks.
  • Antimalarials cause retinal damage over time and prolong the QT; primaquine and tafenoquine hemolyze in G6PD deficiency - test first.
  • Topical scabicides: treat the whole household the same day and wash all bedding in hot water.

Nucleic acid and protein synthesis interference 90

Alkylating and DNA-damaging agents18

Stick a reactive chemical group onto DNA, cross-linking the two strands so they cannot separate. The cell cannot copy or read its own genome and dies - the nitroimidazoles do the same thing to anaerobes using free radicals.

Superglue for DNA: the strands can never unzip again.

  • Damage is not cell-cycle specific, so fast-dividing normal tissue suffers too: marrow, gut lining, hair follicles.
  • Cyclophosphamide's metabolite scars the bladder - hemorrhagic cystitis; push fluids and give mesna.
  • Platinum agents are nephrotoxic and ototoxic with severe delayed nausea - hydrate hard and give aggressive antiemetics.
  • Metronidazole causes a disulfiram reaction: absolutely no alcohol during and for 3 days after.
Antimetabolites (nucleotide and folate analogs)25

Counterfeit building blocks. They look enough like a real nucleotide - or like folate, which is needed to build nucleotides - that the cell picks them up, and then the DNA or RNA chain jams. The same trick that starves a tumor also stops a virus copying itself.

A fake brick in the wall: the builder keeps laying, and the wall collapses.

  • They hit cells in S phase, so marrow suppression and mucositis are expected - check counts and inspect the mouth.
  • Methotrexate blocks folate: leucovorin RESCUE restores normal cells, and folic acid supplements are standard in low-dose weekly use.
  • Weekly methotrexate dosed daily by mistake is fatal - confirm the schedule out loud every time.
  • Nucleoside antivirals (acyclovir, ganciclovir) crystallize in the kidney - push fluids and watch creatinine.
Topoisomerase inhibitors and DNA-intercalating antibiotics10

Wedge between DNA base pairs and freeze the enzymes that unwind and re-seal the double helix. The strand is cut and never repaired, and free radicals from the drug add more breaks.

The zipper is opened and the drug jams it - the DNA can never close again.

  • Anthracyclines are cumulative cardiotoxins - track lifetime dose and get baseline and serial ejection fractions.
  • They are potent vesicants: check blood return constantly, and stop at the first complaint of burning.
  • Red-orange urine after doxorubicin is harmless dye, not bleeding - tell the patient before it happens.
  • Irinotecan causes early cholinergic diarrhea (atropine) and late severe diarrhea (high-dose loperamide) - two different problems.
Antitubulin (mitotic spindle) agents7

Attack the microtubule, the rope the cell uses to pull chromosomes apart. Vincas stop the rope from forming; taxanes freeze it so it can never let go. Either way mitosis stalls and the cell dies.

Vinca = no rope. Taxane = rope stuck. Mitosis stops either way.

  • Microtubules also carry cargo down nerve axons, so peripheral neuropathy is the dose-limiting effect - screen for numbness and constipation.
  • Vinca alkaloids are fatal if given intrathecally and are severe vesicants - IV only, verified by two nurses.
  • Taxanes cause hypersensitivity from the solvent - premedicate with steroid and antihistamine and stay at the bedside for the first minutes.
  • Colchicine uses the same mechanism on neutrophils in gout; diarrhea is the sign the dose is too high.
30S ribosome binders (aminoglycosides, tetracyclines)12

Lock onto the small 30S subunit of the bacterial ribosome. Aminoglycosides make it misread the code and build nonsense protein; tetracyclines block the incoming tRNA so the chain never grows.

Bacteria have 30S and 50S; we have 40S and 60S - that is the whole reason these are safe for us.

  • Aminoglycosides are nephrotoxic and ototoxic - trough levels, daily creatinine, and report tinnitus, vertigo or hearing loss immediately.
  • They also potentiate neuromuscular blockade - a real risk in surgery and myasthenia.
  • Tetracyclines chelate calcium: no dairy, antacids or iron within 2 hours, and avoid in pregnancy and children under 8 (tooth staining).
  • Photosensitivity with tetracyclines is severe - sunscreen and covering clothing, every time.
50S ribosome binders (macrolides, lincosamides, oxazolidinones)12

Bind the large 50S subunit and stop the growing protein chain from moving along the ribosome. Protein production halts, so the bacterium cannot grow or repair itself.

Macrolides, clindamycin and linezolid all crowd the same 50S seat - which is why they compete with each other.

  • Macrolides prolong QT and inhibit CYP3A4 - check the ECG and screen every co-prescription.
  • Clindamycin's wipeout of normal flora is the classic C. difficile setup - report new watery diarrhea at once.
  • Linezolid is a weak MAO inhibitor: watch for serotonin syndrome with SSRIs and avoid tyramine-rich foods.
  • These are bacteriostatic at usual doses - the immune system still has to finish the job, so complete the course.
Gene and RNA-directed agents6

Work on the message rather than the protein. Antisense strands and siRNA bind a specific mRNA so it is destroyed or read differently; gene therapies insert a working copy of the gene into the patient's own stem cells.

Fix the recipe, not the meal.

  • These are given intrathecally, IV or as a one-time infusion by specialty teams - not routine floor medications.
  • Because they are sequence-specific, they only work for patients with the matching mutation - genetic confirmation first.
  • Watch for infusion reactions, thrombocytopenia and renal or hepatic effects depending on the agent.

Immune modulation 113

Corticosteroids (nuclear receptor agonists)21

Slip into the cell, bind a receptor in the cytoplasm, and travel to the nucleus to change which genes are transcribed. Inflammatory proteins are switched off and anti-inflammatory ones switched on - which is why the effect takes hours, not minutes.

Not a fast-acting drug - it rewrites the cell's instructions.

  • Genomic action means it is never a rescue drug in an acute asthma attack; the bronchodilator is.
  • Exogenous steroid shuts down the adrenal axis - never stop abruptly, always taper, and stress-dose during illness or surgery.
  • Cushingoid effects are the mechanism at full volume: high glucose, thin skin, moon face, muscle wasting, osteoporosis, mood swings.
  • Immune suppression masks infection - a normal temperature does not rule sepsis out.
Calcineurin and antiproliferative immunosuppressants8

Cripple the T lymphocyte itself. Calcineurin inhibitors block the signal that makes IL-2, so T cells never get the order to multiply; the antiproliferatives block the purine supply lymphocytes uniquely depend on.

No IL-2 signal, no T cell army.

  • Narrow therapeutic index - trough levels drive dosing, and grapefruit and CYP3A4 drugs wreck them.
  • Both cyclosporine and tacrolimus are nephrotoxic; creatinine and blood pressure at every visit.
  • Deep immunosuppression means opportunistic infection and long-term skin cancer and lymphoma - sun protection and screening.
  • Never stop or substitute brands on your own; even a formulation switch changes the blood level.
Cytokine blockers (TNF, interleukin and IgE)20

Antibodies and fusion proteins that grab a specific inflammatory messenger - TNF-alpha, an interleukin, or IgE - or block its receptor, so the inflammatory conversation is cut off before it starts.

Take one voice out of the immune conversation and the whole argument quiets down.

  • Blocking TNF removes the signal that walls off tuberculosis - screen for latent TB and hepatitis B BEFORE the first dose.
  • No live vaccines during therapy; give inactivated vaccines beforehand where possible.
  • Any fever, cough or wound that will not heal must be reported - infection is the main risk.
  • Most are subcutaneous injections kept refrigerated; teach site rotation and let them warm before injecting.
Tumor-antigen, growth-factor and checkpoint antibodies27

Antibodies aimed at a protein on or around a cancer cell. Some block a growth-factor receptor (HER2, EGFR) or the VEGF that builds tumor blood vessels; checkpoint antibodies instead release the brake the tumor puts on T cells.

-mab is a guided missile; checkpoint drugs take the muzzle off your own T cells.

  • Infusion reactions are the immediate risk - premedicate, run the first dose slowly, and stay at the bedside.
  • Trastuzumab is cardiotoxic (and worse with anthracyclines) - baseline and serial ejection fraction.
  • Checkpoint inhibitors cause autoimmune 'itis' anywhere: colitis, hepatitis, pneumonitis, thyroiditis - new diarrhea or breathlessness needs steroids, not loperamide.
  • EGFR antibodies cause a severe acneiform rash that actually predicts response - treat it, do not stop the drug.
Other therapeutic antibodies and immune globulins22

Ready-made antibodies aimed at a target that is not a cytokine or a tumor: a bone signal, a complement protein, a clotting factor, an integrin, a toxin, or - with pooled human immune globulin - whatever the donors were immune to.

Borrowed immunity: the antibody is made outside the patient and simply handed over.

  • Passive antibody works immediately and wears off in weeks - it is protection, not immunity.
  • Infusion and hypersensitivity reactions are the main risk; have epinephrine available and monitor vitals.
  • Complement blockers (eculizumab, ravulizumab) leave the patient defenceless against meningococcus - vaccinate first and carry a safety card.
  • Never mix immune globulin with live vaccines; wait months or the vaccine will not take.
Cytokines, interferons and colony-stimulating factors15

Give the body more of a signalling protein instead of blocking one. Colony-stimulating factors tell the marrow to build neutrophils or red cells; interferons switch on antiviral and antitumor defences.

The opposite of a blocker - this is the immune system's megaphone.

  • Filgrastim drives marrow production, so deep bone pain is expected - it is a good sign; treat with acetaminophen.
  • Erythropoiesis stimulators need iron to work; check ferritin and do not overshoot hemoglobin (clot and stroke risk).
  • Interferons cause flu-like syndrome, depression and marrow suppression - dose at bedtime, premedicate, screen mood.
  • These are refrigerated proteins: never shake the vial, and teach subcutaneous technique and disposal.

Replacement, binding and metabolic agents 108

Hormone replacement25

Supply the hormone the body is not making enough of. The drug IS the signal - it binds the same nuclear or membrane receptor the natural hormone would, so the dose has to match physiology, not a symptom.

Not blocking anything - just refilling an empty tank.

  • Replacement is lifelong and dose-sensitive: too little leaves symptoms, too much creates the opposite disease.
  • Levothyroxine on an empty stomach, 30-60 minutes before food, away from calcium, iron and PPIs; recheck TSH in 6-8 weeks.
  • Estrogen and testosterone raise clot and cardiovascular risk - screen for VTE history and teach warning signs.
  • Insulin is high-alert: verify the dose and concentration with a second nurse and know the onset and peak of each type.
Bisphosphonates (bone resorption inhibitors)5

Bind tightly to the mineral surface of bone and sit there. When an osteoclast tries to chew that bone up it swallows the drug, its internal enzyme pathway fails, and the osteoclast dies - so breakdown slows and density climbs.

-dronate: poison bait laid on the bone for the cells that eat it.

  • Oral doses are corrosive to the esophagus: first thing in the morning, full glass of plain water, upright for 30-60 minutes, nothing else by mouth.
  • Absorption is terrible and calcium blocks it - separate from food, dairy, antacids and supplements.
  • Correct low calcium and vitamin D first, or the drug will drive the patient hypocalcemic.
  • Rare but real: osteonecrosis of the jaw and atypical femur fracture - dental work before starting, and report new thigh or groin pain.
Vitamins, electrolytes and minerals27

Replace a cofactor or ion the body runs on. Vitamins slot into enzymes as helper molecules; electrolytes and minerals restore the gradients nerves, muscle and the heart depend on.

These are ingredients, not drugs - the body already knew what to do with them.

  • IV potassium is never pushed - always diluted, always on a pump, and it burns if the line is bad.
  • Iron is best absorbed with vitamin C on an empty stomach; expect black stools and constipation, and give IV forms with test-dose vigilance.
  • Fat-soluble vitamins (A, D, E, K) accumulate and can be toxic; water-soluble ones are largely excreted.
  • Correct electrolytes slowly - fast sodium correction damages the brain, fast calcium causes arrhythmia.
Binders, chelators and antidotes19

Physically grab a substance and take it out of circulation. Resins and binders trap it in the gut so it leaves in the stool; chelators and reversal agents latch onto it in the blood so the kidney can clear it.

Chemical handcuffs - nothing is switched on or off, something is simply removed.

  • Binders grab other drugs too - separate every other oral medication by at least 1-4 hours.
  • Potassium binders work over hours, not minutes; a critical K+ still needs calcium, insulin with dextrose and albuterol first.
  • Bile acid sequestrants cause constipation and block fat-soluble vitamin absorption - add fiber, fluids and supplements.
  • For every reversal agent, know the half-life: many antidotes wear off before the poison does, so keep monitoring.
Osmotic, bulk, stimulant and protectant agents18

Work by physics and chemistry rather than by any receptor. Osmotic agents hold water where it is drawn; surfactants and lubricants soften; coating agents form a physical barrier over damaged tissue.

No receptor, no enzyme - water, oil, a barrier, or a poke at the bowel wall.

  • Osmotic laxatives pull water into the bowel, so push fluids or the patient trades constipation for dehydration.
  • Senna and bisacodyl are STIMULANT laxatives - they irritate the bowel wall and stir up peristalsis, which is a different mechanism from the osmotic ones. Give at bedtime for a morning result, and pair one with any opioid.
  • Lactulose also traps ammonia in the gut - in hepatic encephalopathy the goal is 2-3 soft stools a day, not comfort.
  • Mannitol pulls water out of the brain but expands intravascular volume first - use a filter and watch for heart failure and rising osmolality.
  • Sucralfate needs an acid stomach to form its barrier: give on an empty stomach and separate it from antacids and other drugs.
Enzyme replacement and metabolic agents14

Supply an enzyme the patient cannot make, stabilise a misfolded protein, or shift how a cell handles fuel. The target is the body's own metabolism rather than a receptor or a pathogen.

Give back the missing worker, or change what the cell burns.

  • Pancreatic enzymes must be taken with every meal and snack, capsules swallowed whole, never crushed or chewed.
  • Metformin does not cause hypoglycemia alone; hold it around IV contrast and check renal function for lactic acidosis risk.
  • Thiazolidinediones cause fluid retention and weight gain - a real problem in heart failure; weigh daily.
  • Enzyme infusions cause hypersensitivity reactions - premedicate and monitor closely for the first several doses.

Mixed & unclear mechanism 5

Mixed or unclear mechanism5

These drugs either work through several mechanisms at once or through a pathway that is genuinely not settled. They are parked here on purpose - a confidently wrong mechanism is worse than an honest 'not sure'.

If you cannot name the target, do not invent one - look it up before you teach it.

  • Look this drug up individually; there is no class shortcut to lean on.
  • Learn it by its indication and its monitoring parameters instead of by mechanism.
  • Check for interactions from scratch - you cannot predict them from a class here.
Nothing matched that. Try a shorter word — a drug name, a class, or something like "potassium" or "bleeding".
Drug Guide · study summary only, no dosing · always check the current package insert, your course materials and facility policy.