🧠Exam 1
Foundations: how drugs move through the body, how they are named and scheduled, what goes wrong, and the older adult.
Module 1 · 50 questions · 0 drugs · 45 concepts
Pharmacokinetics
Absorption (What is it, what regulates the process, what affects the process?)⭐ HIGH YIELD
Absorption is the movement of a drug from where it was given into the bloodstream. It is regulated by the ROUTE and the drug's ability to cross cell membranes; it is affected by blood flow, surface area, pH/ionization, lipid solubility, food, and GI motility.
- IV = 100% absorbed with no absorption phase, so it has the fastest onset.
- Most oral drugs are absorbed in the small intestine (huge surface area from villi).
- Small, lipid-soluble, non-ionized molecules cross membranes best.
- Slowed by food, low blood flow, decreased motility, and enteric coatings.
Absorption = getting IN. IV skips the line entirely.
Distribution (What is it, what regulates the process, what affects the process?)⭐ HIGH YIELD
Distribution is the movement of drug from the blood into tissues and fluids. It is regulated by blood flow to the tissue, membrane permeability (blood-brain and placental barriers), and PROTEIN BINDING; it is affected by cardiac output, albumin level, body fat vs water, and competing drugs.
- Only FREE (unbound) drug is active. Low albumin = more free drug = toxicity.
- Two highly protein-bound drugs compete; one gets displaced and becomes toxic (warfarin is the classic).
- Highly perfused organs get drug first: heart, liver, kidney, brain.
- The blood-brain barrier blocks large/water-soluble drugs; the placenta blocks almost nothing.
- Lipid-soluble drugs store in fat, so effects last longer in obese and older adults.
Bound = benched. Only free drug plays.
Metabolism (What is it, what regulates the process, what affects the process?)⭐ HIGH YIELD
Metabolism (biotransformation) chemically changes the drug, usually into a more water-soluble, inactive form so it can be excreted. It happens mainly in the LIVER via cytochrome P450 enzymes; it is affected by liver function, age, genetics, and CYP inducers and inhibitors.
- INHIBITORS (grapefruit, ketoconazole, erythromycin, cimetidine, fluoxetine) raise drug levels toward toxicity.
- INDUCERS (St John's wort, rifampin, phenytoin, carbamazepine, smoking) lower drug levels toward treatment failure.
- Prodrugs are the reverse: metabolism ACTIVATES them (codeine to morphine, enalapril to enalaprilat).
- Infants and older adults metabolize slowly, so they need lower doses.
- Liver disease means reduce the dose.
InDucers Decrease the drug. InHibitors Heighten it.
Elimination/Excretion (What is it, what regulates the process, what affects the process?)⭐ HIGH YIELD
Excretion is removal of drug and metabolites from the body. The primary route is the KIDNEY (glomerular filtration, tubular secretion and reabsorption); it is affected by renal function/GFR, age, hydration, urine pH, and competition at the tubules.
- Other routes: bile and feces, lungs (anesthetics, alcohol), breast milk, sweat, saliva.
- Renal impairment causes accumulation: reduce the dose or lengthen the interval. Check creatinine and GFR.
- Older adults have a lower GFR even when serum creatinine looks normal (less muscle mass).
- Enterohepatic recirculation prolongs some drugs by sending them back through the gut.
The kidney is the exit door. Broken door = drug piles up.
First Pass Metabolism / First Pass Effect (What is it? Which dosage forms are affected?)⭐ HIGH YIELD
First-pass effect: a drug absorbed from the GI tract travels through the portal vein to the liver and is partly metabolized BEFORE it ever reaches systemic circulation, so less active drug arrives. ORAL dosage forms are the ones affected.
- This is why the oral dose of a drug is much larger than its IV dose (morphine, propranolol).
- Nitroglycerin is almost entirely destroyed on first pass, which is why it is given sublingually.
- Rectal is only partially affected: the lower rectal veins bypass the liver, the upper ones do not.
| Affected by first pass | Bypasses first pass |
|---|
| Oral tablets, capsules, liquids | IV, IM, subQ |
| Anything absorbed from stomach/intestine | Sublingual and buccal |
| Enteral tube (NG/PEG) doses | Transdermal, inhaled, and largely rectal |
The liver takes its cut first. SL and IV don't pay the toll.
Bioavailability⭐ HIGH YIELD
Bioavailability is the fraction of an administered dose that actually reaches systemic circulation in active form. IV is 100% by definition; oral is lower and more variable because of incomplete absorption plus first-pass metabolism.
- Rough order: IV (100%) > IM/subQ > sublingual, inhaled, transdermal > oral > rectal (variable).
- Anything that reduces absorption or increases first-pass metabolism reduces bioavailability.
- Formulation matters: brand-to-generic switches can matter for narrow-therapeutic-index drugs like levothyroxine, warfarin, and phenytoin.
- Food, gastric pH, and other drugs change oral bioavailability; IV has none of those variables.
Bioavailability = how much made it to the party, not how much left the house.
Medication Administration
Enteral vs Parenteral Routes⭐ HIGH YIELD
Enteral routes deliver drug through the GI tract (oral, sublingual, buccal, NG/PEG tube, rectal). Parenteral routes deliver drug by injection, bypassing the GI tract entirely (IV, IM, subQ, intradermal, epidural, intrathecal).
| Enteral | Parenteral |
|---|
| PO, SL, buccal, NG/G-tube, rectal | IV, IM, subQ, intradermal, intrathecal, epidural |
| Slower and more variable onset | Fast and predictable (IV is immediate) |
| Subject to first-pass metabolism (except SL/buccal) | Bypasses first-pass metabolism |
| Safer, cheaper, patient can self-administer | Requires sterile technique; cannot be taken back once given |
| Needs a working GI tract and gag reflex | Works when the patient is NPO, vomiting, or unconscious |
'Enteral' has ENTER in it, it enters through the gut. 'Par-enteral' means PAST the gut.
Examples of enteral, parenteral, topical, and inhaled dosage forms
Enteral: tablets, capsules, enteric-coated and extended-release tablets, elixirs, suspensions, sublingual tablets, rectal suppositories. Parenteral: IV solutions, IV push, IM and subQ injections, intradermal, depot injections. Topical: creams, ointments, gels, lotions, transdermal patches, eye and ear drops. Inhaled: MDIs, DPIs, nebulizer solutions.
- Never crush enteric-coated or extended-release tablets: it causes dose dumping and toxicity.
- Topical usually means a LOCAL effect; a transdermal patch is applied topically but is meant for a SYSTEMIC effect.
- Inhaled drugs act locally in the lung with fewer systemic side effects, which is the whole advantage in asthma.
| Route | Dosage forms |
|---|
| Enteral | tablet, capsule, EC/ER tablet, elixir, syrup, suspension, sublingual tab, rectal suppository |
| Parenteral | IV piggyback, IV push, IM injection, subQ injection, intradermal (TB test), depot IM |
| Topical | cream, ointment, gel, lotion, paste, transdermal patch, ophthalmic drops, otic drops, vaginal suppository |
| Inhaled | metered-dose inhaler (MDI), dry powder inhaler (DPI), nebulizer solution |
Transdermal Patch Administration🚨 DANGER
Apply a transdermal patch to clean, dry, hairless, intact skin; rotate the site every time; ALWAYS remove the old patch before applying a new one; wear gloves and write the date, time, and your initials on the patch.
- Never cut a patch unless the label allows it. Cutting destroys the controlled-release mechanism.
- Do not apply heat (heating pad, hot tub, fever) over a patch. Heat increases absorption and can cause a fatal overdose with fentanyl.
- Press firmly for 10 to 30 seconds and check that the edges are sealed.
- Dispose of used patches folded sticky-sides together. Leftover drug can kill a child or pet.
- Nitroglycerin patches usually need a 10 to 12 hour patch-free period each night to prevent tolerance.
Old patch OFF before the new patch goes ON. Count patches, not doses.
Depot Medication
A depot medication is a long-acting injectable, usually deep IM, formulated to release drug slowly from the injection site over days, weeks, or months. It is used when adherence is a problem or long-term steady levels are needed.
- Examples: haloperidol decanoate, fluphenazine decanoate, paliperidone palmitate, medroxyprogesterone (Depo-Provera, every 12 weeks), extended-release naltrexone, penicillin G benzathine.
- Give deep IM into a large muscle (often Z-track). Never give a depot preparation IV.
- It cannot be removed once injected, so adverse effects last as long as the depot does.
- Tolerance to the oral short-acting form is usually established first.
Depot = deposit. The muscle is the bank and the drug is withdrawn slowly.
Pharmacodynamics
Half-Life (What is it? How do I calculate the time it takes for a drug to reach a certain serum⭐ HIGH YIELD
Half-life (t1/2) is the time it takes for the serum drug concentration to fall by 50%. It takes about 4 to 5 half-lives to reach steady state on repeated dosing, and about 4 to 5 half-lives to clear a drug after it is stopped.
- Solve the classic question by halving: a drug at 200 mg/L with a 6-hour half-life is 100 at 6 h, 50 at 12 h, 25 at 18 h.
- Half-life determines dosing FREQUENCY. The dose size determines the level.
- Liver or kidney impairment lengthens half-life, so the drug accumulates.
- A loading dose is what you use when you cannot wait 4 to 5 half-lives.
| Half-lives elapsed | % of drug remaining | % of steady state reached |
|---|
| 1 | 50% | 50% |
| 2 | 25% | 75% |
| 3 | 12.5% | 87.5% |
| 4 | 6.25% | 93.75% |
| 5 | ~3% | ~97% |
Cut it in half, then in half again. Five cuts and it is basically gone (or basically full).
Loading Dose⭐ HIGH YIELD
A loading dose is a large initial dose given to reach a therapeutic serum level FAST, instead of waiting 4 to 5 half-lives. Smaller maintenance doses then keep the level there.
- Used for long half-life drugs when you cannot wait: digoxin, amiodarone, phenytoin, vancomycin, heparin bolus.
- The loading dose is based on volume of distribution; the maintenance dose is based on clearance.
- A loading dose does not change the drug's half-life.
- Watch closely after a loading dose: this is when toxicity shows up.
The loading dose fills the tank. Maintenance doses keep topping it off.
Potency vs efficacy⭐ HIGH YIELD
Potency is how MUCH drug it takes to produce an effect. Efficacy is how BIG an effect the drug can produce at its maximum, its ceiling. Efficacy matters more clinically.
- A more potent drug is not a better drug, it just takes fewer milligrams.
- Graphically: potency shifts the dose-response curve left or right; efficacy raises or lowers its ceiling.
| Potency | Efficacy |
|---|
| Amount of drug needed to produce a given effect | Maximum effect the drug can produce at any dose |
| Compares DOSE in mg | Compares RESPONSE, how much relief |
| More potent = smaller dose needed | Higher efficacy = better maximum result |
| 2 mg hydromorphone equals 10 mg morphine, so hydromorphone is more POTENT | Morphine relieves severe pain and ibuprofen never can, so morphine has greater EFFICACY |
Potency = how much. Efficacy = how good. You would rather have the drug that works better than the one you need less of.
Agonist vs antagonist⭐ HIGH YIELD
An agonist binds a receptor and ACTIVATES it, producing a response. An antagonist binds the receptor and BLOCKS it, producing no response and preventing the body's own chemical or an agonist from acting.
- Partial agonist: binds and activates, but with a lower ceiling than a full agonist (buprenorphine).
- A competitive antagonist can be overcome by giving more agonist; a noncompetitive one cannot.
- Antidotes are usually antagonists: naloxone, flumazenil, atropine, protamine.
| Agonist | Antagonist |
|---|
| Binds the receptor AND activates it | Binds the receptor but does NOT activate it |
| Mimics the body's own chemical | Blocks the body's own chemical |
| Turns the response ON or up | Turns the response OFF or down |
| Albuterol (beta-2 agonist) dilates bronchi; morphine (opioid agonist) relieves pain | Metoprolol (beta blocker) slows the heart; naloxone (opioid antagonist) reverses overdose |
Agonist = the key that turns the lock. Antagonist = the key that fits but won't turn, and now nobody else can get in.
Therapeutic index⭐ HIGH YIELD
Therapeutic index (TI) = TD50 divided by ED50 (the toxic dose in 50% of subjects over the effective dose in 50%). A HIGH/wide TI means a large safety margin; a LOW/narrow TI means toxic and therapeutic doses are close together and the drug needs serum level monitoring.
- The therapeutic range or window is the concentration between the minimum effective level and the toxic level.
- For narrow-TI drugs also watch renal and hepatic function, drug interactions, and brand-to-generic switches.
- Practical example: a digoxin level of 2.5 ng/mL is already toxic while the target is roughly 0.5 to 2 ng/mL.
| Narrow (low) therapeutic index | Wide (high) therapeutic index |
|---|
| Small gap between effective and toxic dose | Large gap between effective and toxic dose |
| Requires serum drug levels, peaks and troughs | Routine level monitoring not needed |
| Warfarin, digoxin, lithium, phenytoin, theophylline, vancomycin, gentamicin, carbamazepine | Penicillins, most antihistamines, acetaminophen at label dose |
| Small dose changes or interactions can be dangerous | More forgiving of dose variation |
Narrow index = narrow ledge. One step and the patient falls into toxicity.
Peak and trough⭐ HIGH YIELD
Peak is the HIGHEST serum level, drawn shortly after a dose, and it tells you about toxicity. Trough is the LOWEST level, drawn immediately BEFORE the next dose, and it tells you whether the drug is staying therapeutic and clearing properly.
- Classic peak and trough drugs: vancomycin, gentamicin, tobramycin, amikacin.
- Document the exact time the level was drawn AND the time the last dose was given, or the result is meaningless.
- Follow the order: some protocols hold the next dose until the trough result returns.
| Peak | Trough |
|---|
| Highest concentration | Lowest concentration |
| Drawn after the dose (commonly about 30 min after an IV infusion ends; timing varies by drug and policy) | Drawn 0 to 30 minutes BEFORE the next scheduled dose |
| A high peak signals toxicity: ototoxicity, nephrotoxicity | A high trough means the drug is accumulating; a low trough means subtherapeutic |
| Answers: is it too much? | Answers: is it enough, and is it clearing? |
TROUGH is the low spot in the road, and it comes right before you climb (the next dose).
Onset of action
Onset of action is the time from administration until the drug produces a measurable therapeutic effect, meaning the time it takes for the serum level to cross the minimum effective concentration.
- The three time terms: onset is when it starts, peak is maximum effect, duration is how long it lasts.
- Route drives onset: IV seconds to minutes, IM/subQ minutes, sublingual 1 to 5 minutes, oral 30 to 60 minutes, transdermal hours.
- Use onset to time nursing care: give the analgesic so its peak lines up with the dressing change or physical therapy.
- Reassess pain at the drug's expected onset or peak, not five minutes after a PO dose.
Onset = when it starts working. Peak = when it works hardest. Duration = when it quits.
Adverse Effects
Tolerance vs dependence⭐ HIGH YIELD
Tolerance means the body needs MORE drug over time to get the same effect. Dependence means the body has adapted so that stopping the drug causes WITHDRAWAL. Neither one is the same as addiction.
- Addiction (substance use disorder) is compulsive use, craving, and continued use despite harm. It is behavioral, not a lab value.
- Cross-tolerance: tolerance to one drug in a class carries over to others in that class.
- Tachyphylaxis is rapid tolerance after only a few doses, classically with nitrates.
- Physical dependence is expected and normal in a patient on long-term opioids and does not mean they are addicted.
| Tolerance | Dependence |
|---|
| Decreased response to the same dose | Physiologic adaptation to the drug's presence |
| Sign: patient needs a higher dose for the same relief | Sign: withdrawal symptoms when the drug is stopped or reduced |
| Seen with opioids, nitrates, benzodiazepines | Seen with opioids, benzodiazepines, alcohol, beta blockers, corticosteroids |
| Managed by dose adjustment or drug rotation | Managed by TAPERING, never abrupt discontinuation |
Tolerance = 'need more.' Dependence = 'can't stop without withdrawal.' Addiction = 'can't stop and it's wrecking my life.'
Allergic Responses⭐ HIGH YIELD
An allergic (hypersensitivity) response is an IMMUNE-mediated reaction to a drug. It requires a prior sensitizing exposure, is not dose-related, and ranges from a mild rash to fatal anaphylaxis.
- Type I (IgE, immediate): urticaria, angiedema, anaphylaxis, within minutes to an hour.
- Type II and III (cytotoxic and immune complex): hemolytic anemia, thrombocytopenia, serum sickness, drug fever.
- Type IV (delayed, T-cell): contact dermatitis, morbilliform rash, and SJS/TEN, appearing days to weeks later.
- An allergy is NOT a side effect or intolerance. GI upset from erythromycin is not an allergy. Always ask WHAT happened, not just 'are you allergic,' and document the actual reaction.
- Top offenders: penicillins and cephalosporins, sulfonamides, NSAIDs, contrast media, neuromuscular blockers.
First exposure sensitizes, second exposure reacts. That is why 'I've taken it before' does not protect the patient.
Mild allergy⭐ HIGH YIELD
A mild allergic reaction involves the SKIN AND MUCOUS MEMBRANES ONLY: itching, hives (urticaria), flushing, localized rash, mild swelling, watery eyes, runny nose, with NO airway, breathing, or blood pressure involvement.
- Treatment: stop the drug, antihistamine (diphenhydramine or cetirizine), sometimes a topical or oral corticosteroid, and keep monitoring.
- Add it to the allergy list with a description of what happened.
- A mild reaction can become severe on re-exposure, so never dismiss one.
| Mild reaction | Anaphylaxis |
|---|
| Hives, itching, flushing, localized rash | Skin findings PLUS airway, breathing, or circulation involvement |
| Vital signs stable | Hypotension, tachycardia, dizziness, near-syncope |
| Stop the drug, give an antihistamine, monitor | Give IM EPINEPHRINE first, then antihistamine and corticosteroid |
| Notify the provider and document | Call the rapid response team; this is life-threatening |
Skin only = mild. Skin plus breathing or blood pressure = epinephrine.
Anaphylaxis (What are the signs & symptoms?)🚨 DANGER
Anaphylaxis is a rapid, life-threatening IgE-mediated reaction involving two or more body systems, usually within minutes of exposure. Give IM EPINEPHRINE into the anterolateral thigh IMMEDIATELY. Do not wait, and do not give an antihistamine first.
- Skin/mucosa (most common): hives, flushing, intense itching, angiedema of lips, tongue, and face.
- Respiratory: throat tightness, hoarseness, stridor, wheezing, cough, dyspnea. Laryngeal edema is what kills first.
- Cardiovascular: hypotension, tachycardia, weak thready pulse, dizziness, syncope, shock. GI: cramping, nausea, vomiting, diarrhea. Plus a reported sense of impending doom.
- Adult epinephrine: 0.3 to 0.5 mg IM of the 1 mg/mL (1:1000) concentration in the thigh, repeat every 5 to 15 minutes as needed.
- Then: stop the drug, ABCs, high-flow oxygen, IV fluids, supine with legs elevated. Antihistamine and corticosteroid are ADJUNCTS only. Biphasic reactions can recur up to 72 hours later, so observe rather than discharging immediately.
Epi in the THIGH and don't ask why. Benadryl treats the itch; epinephrine treats the dying.
Stevens Johnson Syndrome🚨 DANGER
Stevens-Johnson syndrome is a rare, life-threatening drug reaction causing widespread blistering and sloughing of skin AND mucous membranes. Stop the drug immediately and never rechallenge. SJS involves less than 10% of body surface area; TEN involves more than 30%.
- Prodrome first: fever, sore throat, malaise, burning eyes. It looks like the flu, typically 1 to 3 weeks after starting the drug.
- Then: painful targetoid or purpuric macules, flaccid blisters, and a positive Nikolsky sign (skin sloughs with light lateral pressure).
- Mucosal involvement is the tip-off: mouth, lips, eyes, and genitals ulcerate.
- Top triggers: sulfonamides (TMP-SMX), allopurinol, anticonvulsants (lamotrigine, carbamazepine, phenytoin, phenobarbital), nevirapine, oxicam NSAIDs, penicillins, cephalosporins, quinolones.
- Manage like a major burn: burn or intensive care unit, fluid and electrolyte replacement, wound care, ophthalmology consult, no prophylactic antibiotics. Teach every patient starting lamotrigine or allopurinol to report ANY new rash immediately.
New rash + fever + sore mouth + burning eyes after a new drug = stop the drug and call now.
Bone Marrow Suppression (What cell types are affected? What are the signs and symptoms?)🚨 DANGER
Bone marrow suppression (myelosuppression) is decreased production of blood cells by the marrow. All three cell lines are affected: neutrophils/WBCs (infection), RBCs (anemia), and platelets (bleeding).
- Fever in a neutropenic patient is an EMERGENCY: cultures and broad-spectrum antibiotics within one hour.
- Nadir, the lowest counts, is usually 7 to 14 days after chemotherapy.
- Nursing: neutropenic precautions, no rectal temps or suppositories, soft toothbrush, electric razor, no aspirin or NSAIDs, fall precautions.
- Common causes: chemotherapy, radiation, chloramphenicol, clozapine, methimazole/PTU, carbamazepine, linezolid, zidovudine, methotrexate, immunosuppressants.
| Cell line affected | Resulting problem | Signs and symptoms |
|---|
| Neutrophils (WBC) | Neutropenia: ANC under 1,500; severe under 500 | Fever 100.4 F (38 C) or higher, sore throat, cough, burning urination, often with NO pus or redness |
| Red blood cells | Anemia | Fatigue, pallor, dyspnea on exertion, tachycardia, dizziness, cold intolerance |
| Platelets | Thrombocytopenia: under 150,000; bleeding risk under 50,000; spontaneous bleeding under 20,000 | Easy bruising, petechiae, gum and nose bleeds, blood in urine or stool, prolonged bleeding |
Low WBC = infection. Low RBC = exhaustion. Low platelets = bleeding. Three lines, three problems.
Nephrotoxicity (What is it? What groups of drugs are nephrotoxic?)⭐ HIGH YIELD
Nephrotoxicity is drug-induced kidney injury: rising creatinine and BUN with falling urine output and GFR. Monitor renal function, keep the patient hydrated, and avoid stacking nephrotoxic drugs.
- Nephrotoxic groups to know: aminoglycosides (gentamicin, tobramycin, amikacin), vancomycin, amphotericin B, NSAIDs, IV contrast media, cisplatin, cyclosporine and tacrolimus, IV acyclovir, lithium, sulfonamides, and ACE inhibitors/ARBs in low-flow states.
- Signs: rising serum creatinine and BUN, urine output under 30 mL/hr, edema, weight gain, electrolyte derangement.
- Nursing: baseline and serial BUN/creatinine, strict intake and output, daily weights, hydration, trough levels, and do not combine nephrotoxins.
- Many nephrotoxic drugs are also OTOTOXIC: aminoglycosides, vancomycin, loop diuretics, cisplatin, high-dose aspirin. Ask about tinnitus, vertigo, and hearing loss.
The kidney killers travel together: Aminoglycosides, Vancomycin, Amphotericin ('ampho-terrible'), NSAIDs, Contrast, Cisplatin.
Cardiotoxicity⭐ HIGH YIELD
Cardiotoxicity is drug-induced damage to heart muscle or conduction. It shows up three ways: cardiomyopathy and heart failure, arrhythmias and conduction block, or QT prolongation leading to torsades de pointes.
- Cardiomyopathy/HF: anthracyclines (doxorubicin, with a lifetime cumulative dose limit), trastuzumab, cyclophosphamide, some tyrosine kinase inhibitors.
- QT prolongation and torsades: amiodarone, sotalol, haloperidol, droperidol, methadone, macrolides, fluoroquinolones, ondansetron, TCAs, citalopram.
- Rate and conduction: digoxin toxicity, beta blockers, and non-dihydropyridine calcium channel blockers (verapamil, diltiazem) cause bradycardia and heart block.
- Monitoring: baseline and serial echocardiogram/ejection fraction for anthracyclines; ECG with QTc plus potassium and magnesium for QT drugs.
- Teach the patient to report new dyspnea, orthopnea, swelling, weight gain over 2 to 3 lb in a day, palpitations, or syncope.
Doxorubicin is 'the red devil': cardiotoxic, and dose-limited for life.
Torsade de Pointes
Drug Interactions⭐ HIGH YIELD
A drug interaction occurs when one drug, food, or herb changes another drug's effect. Interactions can be additive/synergistic, antagonistic, or pharmacokinetic (altered absorption, protein binding, CYP metabolism, or excretion). Under the torsade de pointes heading on this handout: combining two QT-prolonging drugs, or adding a CYP3A4 inhibitor to a QT drug, is a classic cause of torsades.
- Torsades combinations to know: macrolide or fluoroquinolone plus amiodarone or sotalol; haloperidol or methadone plus ondansetron; any QT drug plus HYPOKALEMIA or HYPOMAGNESEMIA.
- A QTc over 500 ms is the danger threshold. Treat torsades with IV magnesium sulfate, and defibrillate if the patient is pulseless.
- Pharmacokinetic: CYP inhibitors (grapefruit, ketoconazole, erythromycin, cimetidine, fluoxetine) raise levels; CYP inducers (St John's wort, rifampin, phenytoin, carbamazepine) lower them.
- Pharmacodynamic: warfarin plus an NSAID causes bleeding; opioid plus benzodiazepine causes respiratory depression; two serotonergic drugs cause serotonin syndrome.
- Correct potassium and magnesium before blaming the drug alone.
Two QT drugs plus a low potassium equals twisting ribbons on the monitor.
Examples of common drug-food interactions
Medication Errors (What are common causes? What are some prevention strategies?)⭐ HIGH YIELD
Medication errors are preventable events that lead to inappropriate medication use or patient harm. The most common causes are communication failures, look-alike/sound-alike drugs, illegible or verbal orders, distraction and interruption, and heavy workload. Prevention centers on the rights of medication administration, barcode scanning, and independent double checks.
- Common causes: decimal and dose miscalculations, unapproved abbreviations, LASA drugs (hydralazine/hydroxyzine, celecoxib/citalopram), verbal or telephone orders, interruptions during administration, and incomplete medication reconciliation at transitions of care.
- Prevention: the rights (patient, drug, dose, route, time, documentation, reason, response), two identifiers, barcode scanning, read-back of verbal orders, the 'do not use' abbreviation list, a leading zero (0.5 mg) and never a trailing zero (never 5.0 mg).
- High-alert drugs (insulin, heparin, opioids, chemotherapy, concentrated electrolytes) require an INDEPENDENT double check by a second nurse.
- Report every error and near-miss. Non-punitive reporting is what fixes the system.
- After an error: assess and stabilize the PATIENT first, then notify the provider, then complete the incident report. Do not chart 'incident report filed' in the medical record.
Patient first, provider second, paperwork third.
Geriatric Pharmacology
Physiological changes of the elderly⭐ HIGH YIELD
Aging changes all four pharmacokinetic phases: absorption slows, distribution shifts (less body water, more fat, less albumin), hepatic metabolism declines, and renal excretion declines. The result is that drugs last longer and accumulate, so you start low and go slow.
- The aging CNS is more sensitive, so benzodiazepines, anticholinergics, and opioids cause more sedation, confusion, and falls.
- Blunted baroreceptor response means more orthostatic hypotension. Thinner skin changes topical and transdermal absorption.
- Practical nursing: use renally adjusted dosing, review the whole med list at every visit, and treat new confusion or falls as a drug side effect until proven otherwise.
| Phase | Change with aging | Consequence |
|---|
| Absorption | Less gastric acid, slower motility, less GI blood flow | Slower onset; usually the least significant change |
| Distribution | Less total body water, more body fat, less serum albumin | Water-soluble drugs are more concentrated, fat-soluble drugs are stored and prolonged, more free active drug |
| Metabolism | Smaller liver, less hepatic blood flow, reduced CYP activity | Higher levels and longer half-life; first-pass drugs hit harder |
| Excretion | Reduced GFR and renal blood flow | Accumulation; a 'normal' creatinine can still hide a poor GFR because of low muscle mass |
Less water, less albumin, less liver, less kidney: the same dose hits harder and stays longer.
Groups of medications to avoid in the elderly (i.e., Beers criteria)⭐ HIGH YIELD
The Beers Criteria (American Geriatrics Society) is a list of potentially inappropriate medications for adults 65 and older, where the risk outweighs the benefit. The biggest categories are anticholinergics, benzodiazepines and Z-drugs, antipsychotics, NSAIDs, and certain cardiac and endocrine drugs.
- First-generation antihistamines (diphenhydramine, hydroxyzine) and other strong anticholinergics (oxybutynin, amitriptyline and other TCAs, cyclobenzaprine, muscle relaxants): confusion, dry mouth, urinary retention, constipation, falls.
- Benzodiazepines (lorazepam, diazepam) and Z-drugs (zolpidem): falls, fractures, delirium.
- Antipsychotics used for behavioral symptoms of dementia: increased stroke risk and mortality.
- Chronic NSAIDs: GI bleeding, kidney injury, worsening heart failure and hypertension.
- Others: meperidine (neurotoxic metabolite), sliding-scale insulin as the only regimen, long-acting sulfonylureas like glyburide and chlorpropamide (prolonged hypoglycemia), digoxin above 0.125 mg/day, PPIs beyond 8 weeks without indication. Beers is a caution and review list, not an absolute ban. It prompts you to find a safer alternative.
Anticholinergics in the elderly: blind as a bat, dry as a bone, red as a beet, mad as a hatter, and then they fall.
Polypharmacy⭐ HIGH YIELD
Polypharmacy is the use of multiple medications, commonly defined as 5 or more at once, or the use of more drugs than are clinically necessary. It multiplies the risk of interactions, adverse effects, nonadherence, falls, and prescribing cascades.
- Prescribing cascade: a drug side effect is mistaken for a new disease and treated with another drug (metoclopramide causes EPS, which gets treated with an anti-Parkinson drug).
- Risk factors: multiple prescribers, multiple pharmacies, OTC and herbal use, several chronic conditions, and no medication reconciliation.
- Nursing role: a 'bring all your bottles' medication review, reconciliation at every transition, and specifically asking about OTCs, supplements, eye drops, and creams, which patients rarely volunteer.
- Deprescribing is legitimate care. Fewer drugs is often better outcomes in older adults.
Every new symptom in an older adult is a drug side effect until proven otherwise.
Herbal Supplements - Focus on the indications and contraindications
Aloe
Aloe is used TOPICALLY for burns, minor wounds, and skin irritation, and ORALLY (aloe latex) as a stimulant laxative. The oral form is the dangerous one: chronic use causes cramping, diarrhea, and HYPOKALEMIA.
- Hypokalemia from aloe latex potentiates DIGOXIN TOXICITY and adds to potassium-wasting diuretics and corticosteroids.
- May lower blood glucose, which is additive with insulin and oral antidiabetics.
- Contraindicated in pregnancy (uterine stimulation), bowel obstruction, inflammatory bowel disease, appendicitis, and with chronic laxative use.
- Topical gel is generally safe; oral aloe latex products have largely been removed from the US market as OTC laxatives.
Aloe on the skin, fine. Aloe down the hatch means diarrhea and a dangerously low potassium.
Black cohosh (How does it work?)
Black cohosh is taken for MENOPAUSAL symptoms (hot flashes, night sweats, mood swings) and for PMS and dysmenorrhea. It appears to work centrally on serotonin receptors and as a selective estrogen-receptor modulator rather than as a true estrogen.
- Contraindicated in pregnancy (may stimulate uterine contractions) and in breastfeeding.
- Biggest safety concern is HEPATOTOXICITY. Teach the patient to report jaundice, dark urine, right upper quadrant pain, and unusual fatigue. Avoid in liver disease and with other hepatotoxic drugs.
- Use cautiously in estrogen-sensitive cancers (breast, uterine) and with hormone therapy or tamoxifen.
- May add to antihypertensives (hypotension) and may reduce the effectiveness of some statins.
- Common effects: GI upset, headache, dizziness, rash.
Black cohosh cools the flash but watch the liver.
Cannabis
Cannabis and prescription cannabinoids are used for chemotherapy-induced nausea and vomiting, appetite stimulation in AIDS-related wasting, chronic and neuropathic pain, spasticity in multiple sclerosis, and specific seizure disorders (cannabidiol for Lennox-Gastaut and Dravet syndromes).
- Prescription forms: dronabinol and nabilone (synthetic THC) and cannabidiol (Epidiolex).
- Adverse effects: sedation, dizziness, orthostatic hypotension, tachycardia, impaired coordination and judgment, dry mouth, euphoria or dysphoria, cognitive impairment.
- Additive CNS depression with alcohol, opioids, and benzodiazepines, which is a fall and respiratory risk.
- Avoid in pregnancy and breastfeeding, in psychotic disorders (can precipitate psychosis), and in unstable cardiac disease.
- Cannabinoid hyperemesis syndrome: paradoxical cyclic vomiting relieved by hot showers, seen in chronic heavy users.
Echinacea⭐ HIGH YIELD
Echinacea is taken to PREVENT or shorten the common cold and upper respiratory infections by stimulating the immune system. That is exactly why it is CONTRAINDICATED in autoimmune disease and in transplant or immunosuppressed patients.
- Avoid in multiple sclerosis, lupus, rheumatoid arthritis, HIV, tuberculosis, and with cyclosporine, tacrolimus, or corticosteroids: it works against the drugs suppressing the immune system.
- Cross-allergy with ragweed, daisies, chrysanthemums, and marigolds (Asteraceae family).
- Inhibits CYP1A2 and CYP3A4, so it can raise levels of some drugs. Limit continuous use (commonly 8 weeks or less) because of reported hepatotoxicity.
- Evidence for actual benefit is weak and inconsistent.
- Common effects: GI upset, rash, and a temporary tingling of the tongue.
Echinacea REVS the immune system, so never give it to someone whose immune system we are trying to shut down.
Feverfew
Feverfew is taken to PREVENT migraines (prophylaxis, not acute treatment) and for arthritis and fever. The tested safety issue is bleeding: it inhibits platelet aggregation and adds to anticoagulants, antiplatelets, and NSAIDs.
- Stop about 1 to 2 weeks before surgery or an invasive procedure.
- Contraindicated in pregnancy (uterine stimulant) and in ragweed/Asteraceae allergy.
- Abrupt discontinuation after long-term use causes 'post-feverfew syndrome': rebound headache, anxiety, insomnia, and muscle stiffness. Taper instead.
- Chewing fresh leaves causes mouth ulcers and loss of taste; GI upset is common.
Feverfew prevents the migraine before it starts, but it thins the blood.
Garlic⭐ HIGH YIELD
Garlic is taken to lower cholesterol and blood pressure and for general cardiovascular prevention. The tested problem is BLEEDING: it inhibits platelet aggregation and adds to warfarin, aspirin, clopidogrel, heparin, and NSAIDs.
- Stop about 7 to 10 days before surgery or an invasive procedure.
- May lower blood glucose, which is additive with insulin and oral antidiabetics.
- Reduces levels of saquinavir and other HIV protease inhibitors, risking treatment failure.
- May lower blood pressure, which is additive with antihypertensives.
- Common effects: breath and body odor, heartburn, and GI upset.
The G-herbs that make you bleed: Garlic, Ginger, Ginkgo, Ginseng (plus feverfew, fish oil, and vitamin E).
Ginger
Ginger is taken for NAUSEA AND VOMITING (motion sickness, postoperative nausea, and morning sickness of pregnancy) and for osteoarthritis pain. Like the other G-herbs, high doses increase bleeding risk.
- It is one of the safer options for pregnancy-related nausea, but doses should stay modest and be cleared with the provider.
- Caution with warfarin, aspirin, clopidogrel, and NSAIDs; hold before surgery.
- May lower blood glucose and blood pressure, so it is additive with antidiabetics and antihypertensives.
- High doses cause heartburn and GI upset. Use caution with gallstones because it increases bile flow.
Ginger for the gut. Still a G-herb, still bleeds.
Gingko Biloba (How does it work?)⭐ HIGH YIELD
Ginkgo biloba is taken for MEMORY and dementia, cognitive decline, and intermittent claudication. It works by increasing blood flow (vasodilation) and inhibiting platelet-activating factor, and that antiplatelet action is exactly why it is dangerous: BLEEDING.
- Serious risk of intracranial and postoperative bleeding with warfarin, aspirin, clopidogrel, heparin, NSAIDs, and vitamin E. Stop 1 to 2 weeks before surgery or any invasive procedure.
- LOWERS THE SEIZURE THRESHOLD. Avoid in seizure disorders and with bupropion, TCAs, and tramadol.
- Avoid with SSRIs and MAOIs (serotonin effects) and in pregnancy.
- Adverse effects: headache, dizziness, GI upset, palpitations.
- Never eat raw or roasted ginkgo SEEDS: they are toxic and can cause seizures.
Ginkgo helps you think and helps you bleed.
Ginseng
Ginseng is taken for energy, stress and fatigue (an 'adaptogen'), concentration, immune support, and to lower blood glucose in type 2 diabetes. Watch for HYPOGLYCEMIA with antidiabetic drugs and an altered INR with warfarin.
- Lowers blood glucose, which is additive with insulin, sulfonylureas, and metformin. Teach hypoglycemia signs.
- Reduces warfarin effectiveness (lowers the INR), risking clots. Either way, the INR must be monitored.
- Avoid with MAOIs (headache, mania, tremor) and with stimulants or caffeine (nervousness, insomnia, tachycardia).
- Can raise blood pressure and cause insomnia. Avoid in uncontrolled hypertension and do not take at bedtime.
- Avoid in pregnancy, breastfeeding, and hormone-sensitive cancers.
Ginseng is the energizer: it drops the sugar, raises the pressure, and messes with the INR.
Glucosamine
Glucosamine, usually combined with chondroitin, is taken for OSTEOARTHRITIS, most often of the knee, for joint pain and cartilage support. Two contraindications get tested: SHELLFISH ALLERGY and diabetes.
- Most products are derived from shellfish and crustacean shells. Always ask about shellfish allergy.
- May raise blood glucose and insulin resistance, so monitor glucose in diabetics.
- Chondroitin is structurally similar to heparin, adding bleeding risk with warfarin and antiplatelets. Monitor the INR.
- Takes weeks to months to show any benefit, and the evidence is mixed.
- Avoid in pregnancy and breastfeeding due to insufficient data.
Glucosamine = shells and sugar: shellfish allergy and glucose control.
Kava🚨 DANGER
Kava is taken for anxiety, restlessness, and insomnia. It is the herb most associated with SEVERE HEPATOTOXICITY, including liver failure requiring transplant, and it is banned or restricted in several countries.
- Never combine with alcohol, acetaminophen, statins, or other hepatotoxic drugs. Avoid in any liver disease.
- Teach the patient to report jaundice, dark urine, pale stools, right upper quadrant pain, nausea, and unusual fatigue.
- Additive CNS depression with benzodiazepines, barbiturates, opioids, and alcohol: sedation, falls, respiratory depression.
- May worsen Parkinson's symptoms (dopamine antagonism) and causes a scaly yellowed rash (kava dermopathy) with chronic use.
- Contraindicated in pregnancy, breastfeeding, and depression. No driving.
Kava calms the mind and kills the liver.
Omega-3 Fatty Acids
Omega-3 fatty acids (fish oil, EPA and DHA) are taken to lower TRIGLYCERIDES, to reduce cardiovascular risk, and for rheumatoid arthritis joint pain. The main caution is increased bleeding at high doses.
- Prescription forms (icosapent ethyl, omega-3-acid ethyl esters) are used for triglycerides of 500 mg/dL or higher.
- High doses inhibit platelet aggregation: caution with warfarin, aspirin, clopidogrel, and NSAIDs, and hold before surgery.
- Common effects: fishy aftertaste and burps, GI upset, diarrhea. Taking with meals or freezing the capsules helps.
- High doses increase the risk of atrial fibrillation and can slightly raise LDL.
- Use caution with fish or shellfish allergy.
Fish oil drops the triglycerides and thins the blood.
Saw Palmetto⭐ HIGH YIELD
Saw palmetto is taken for BENIGN PROSTATIC HYPERPLASIA: urinary frequency, nocturia, and weak stream. It is thought to act like a mild 5-alpha-reductase inhibitor, blocking conversion of testosterone to DHT.
- Contraindicated in pregnancy and in women who could become pregnant. The hormonal effect can harm a male fetus, and pregnant women should not even handle the capsules.
- Can LOWER the PSA level and mask or delay a prostate cancer diagnosis. Tell the provider before PSA testing.
- Mild antiplatelet effect: caution with anticoagulants and antiplatelets, and hold before surgery.
- May add to finasteride, dutasteride, and alpha blockers, and may interact with hormonal contraceptives and estrogen therapy.
- Never let it delay evaluation of urinary retention or hematuria.
Saw palmetto saves the stream and saws down the PSA number.
St John’s wort🚨 DANGER
St John's wort is taken for MILD TO MODERATE DEPRESSION, anxiety, and sleep problems. It is the single most dangerous herb for drug interactions: it is a potent CYP3A4 and P-glycoprotein INDUCER, so it makes other drugs stop working, and it is serotonergic, so it causes serotonin syndrome.
- Drugs it can render INEFFECTIVE: oral contraceptives (breakthrough pregnancy), warfarin, digoxin, cyclosporine and tacrolimus (transplant rejection), HIV protease inhibitors and NNRTIs, theophylline, statins, anticonvulsants, and some chemotherapy.
- Serotonin syndrome risk with SSRIs, SNRIs, TCAs, MAOIs, triptans, tramadol, and linezolid: agitation, hyperthermia, hyperreflexia, clonus, diaphoresis, tachycardia.
- Causes PHOTOSENSITIVITY. Teach sunscreen and protective clothing.
- Contraindicated in pregnancy and bipolar disorder (can trigger mania). Stop about 5 days before surgery because of anesthesia interactions.
- Never stop a prescribed antidepressant in order to start it, and taper rather than stopping abruptly.
St John's wort makes everything else WORTHLESS, and stacked with an SSRI it makes serotonin syndrome.
Valerian
Valerian is taken for INSOMNIA and anxiety. It shortens the time it takes to fall asleep, most likely by increasing GABA activity. The main issue is additive CNS depression with sedatives and alcohol.
- Avoid combining with benzodiazepines, barbiturates, Z-drugs, opioids, antihistamines, alcohol, and kava: oversedation, falls, respiratory depression.
- Stop before surgery because it interacts with anesthesia, and taper after long-term use since abrupt stopping can cause benzodiazepine-like withdrawal.
- Effects: morning grogginess, headache, dizziness, vivid dreams, GI upset, and a strong unpleasant odor. No driving.
- Avoid in pregnancy, breastfeeding, and liver disease. Rare hepatotoxicity has been reported.
- Takes days to weeks for full effect, so it is not for one bad night.
Valerian is herbal Ambien: sedating, and it doubles up with everything else sedating.
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Where this came from. Drug cards are pulled from your own drug guide, which was fact-checked against FDA labeling. The concept answers were written for this guide from your course textbook,
Pharmacology (WTCS, 2e), so they should match your lectures. Check anything that contradicts what your instructor said — they write the exam.