Four drug families, four completely different jobs — and students lose points because they
learn them as a list of names instead of as four answers to four different symptoms. So learn it this
way instead: antihistamines block the itch/sneeze/drip, decongestants shrink swollen nasal
vessels, antitussives turn a useless cough down, and expectorants thin mucus so a useful cough
works better. Get the symptom right and the drug picks itself.
🤧 ANTIHISTAMINEBlocks H₁. Fixes itch, sneeze, drip,
hives. 1st gen = SEDATING. 2nd gen = non-sedating.
👃 DECONGESTANTVasoCONSTRICTOR. Fixes the BLOCK.
Sprays: 3 days max or you get rebound. Caution in hypertension.
😤 ANTITUSSIVEDextromethorphan · codeine. Turns the cough
off. Only for a DRY, useless cough.
💧 EXPECTORANTGuaifenesin. Thins the mucus so the cough
works. Water is part of the dose — about 2 L/day.
🤧
PART 1 · ANTIHISTAMINES
BLOCK IT
Histamine causes four symptoms. The drug blocks the receptor those four symptoms come through.
The whole allergic reaction happens in seconds because
histamine is already made and stored in those gold granules — nothing has to be manufactured. That is why
an antihistamine works best before the exposure.
💊 The mechanism in one sentence
Antihistamines are H₁-receptor blockers. They sit in the receptor so histamine can't — which stops
the itching, sneezing, runny nose, watery eyes and hives.
What they do not do: they don't destroy histamine, they don't undo a reaction that has already
fully happened, and they are not the treatment for anaphylaxis — that is epinephrine.
🧠 The antihistamine takes the seat before histamine can sit down.
🫁 What they are actually used for
Allergic rhinitis — hay fever, seasonal and perennial allergy.
Urticaria (hives) and allergic itching.
Allergic conjunctivitis — itchy, watery eyes.
Mild allergic reactions, and as an adjunct after epinephrine in anaphylaxis — never instead of it.
First-generation ones are also used for motion sickness, nausea and as sleep aids —
because of the very sedation that makes them a nuisance in allergy.
🧠 Itch, sneeze, drip, hive. Four symptoms, one drug family.
One physical property — how easily the molecule crosses the
blood–brain barrier — explains the entire difference between the two generations, including all the
anticholinergic side effects of the older ones.
Peptic ulcer disease and bowel obstruction — motility slows further.
Older adults — a leading cause of drug-induced confusion and falls.
SAME PICTURENG-143 —
"can't see, can't pee, can't spit, can't poop" applies here too.
⭐ Safety teaching for a sedating antihistamine
No driving or machinery until you know how it affects you.
No alcohol, no other sedatives — the effects add.
Change position slowly; these drugs can cause dizziness and orthostatic hypotension.
Take with food if it upsets the stomach.
Increase fluids for the dry mouth; sugar-free gum or hard candy helps.
Take it before the exposure where possible — before mowing the lawn, before the cat's house.
🧠 Sedating + alcohol + an older adult = a fall waiting to happen.
❌ What antihistamines are NOT
An antihistamine is not the treatment for anaphylaxis. Epinephrine is.
They are also poor decongestants — they barely touch a blocked nose, because the block is a
swollen-blood-vessel problem, not a histamine problem. That is exactly why combination products pair an
antihistamine with a decongestant ("-D" products).
A patient may be taking a first-generation antihistamine and an inhaled anticholinergic and
an antidepressant with anticholinergic effects. Each is mild; together they cause retention, constipation
and confusion.
Add up the anticholinergic burden across the whole medication list, not drug by drug.
🧠 Three "mild" dry drugs make one very dry patient.
👃
PART 2 · DECONGESTANTS
SHRINK IT
A blocked nose is a plumbing problem — so the fix is a vasoconstrictor, not an antihistamine.
Look at panel 2: there is almost no mucus in the picture.
The nose is blocked because those turbinate vessels are engorged. Understand this one image and the entire drug
class makes sense — including every one of its cautions.
💊 The mechanism
Decongestants are alpha-adrenergic agonists — sympathetic drugs that constrict blood vessels.
Constrict the vessels in the swollen turbinates and the tissue shrinks, so the airway opens.
Two routes: oral (pseudoephedrine, phenylephrine) and topical nasal spray
(oxymetazoline, phenylephrine).
🧠 DEcongestant = DEflates the swollen tissue.
🚨 A vasoconstrictor doesn't stay in the nose
An oral decongestant constricts vessels everywhere and stimulates the sympathetic system — so it
raises blood pressure and heart rate, and it can cause insomnia, restlessness and tremor.
Use caution or avoid in: hypertension · coronary artery disease · dysrhythmias · hyperthyroidism ·
closed-angle glaucoma · diabetes · BPH, and in older adults generally.
Teach patients to check the label of any over-the-counter cold product — the "-D" on the box means a
decongestant is in it.
🧠 If it can squeeze a nose vessel, it can squeeze a coronary artery.
Rebound congestion is a topical spray phenomenon.
It is the single most-tested teaching point about decongestants, and this shape — each rebound worse than the
last — is why the 3-day rule exists.
🚨 Rebound congestion — rhinitis medicamentosa
The rule: nasal spray decongestants for no more than about 3 days.
With continued use, the vessels adapt. Each dose wears off leaving more swelling than before, so
the patient sprays more often and the cycle tightens — ending with a nose more blocked than it was before
treatment started.
Coming off it means a few genuinely uncomfortable days. Saline spray, a humidifier and reassurance carry
them through.
🧠 THREE days, then STOP — even if it's still blocked.
✅ The non-drug measures that actually help
Saline nasal spray or rinse — no rebound, safe to use as often as needed.
Humidified air, especially overnight.
Increase fluids to thin secretions.
Elevate the head of the bed for night-time congestion.
Remove the trigger — dust covers, pet-free bedroom, close windows on high-pollen days.
For ongoing allergic congestion, an intranasal corticosteroid is the long-term answer, not a
decongestant spray. It takes days to work, so it has to be taken every day.
🧠 Saline is free, safe and unlimited. Always offer it first.
💊 Antihistamine + decongestant combinations
Products labeled "-D" (loratadine-D, cetirizine-D, fexofenadine-D) contain a second-generation
antihistamine plus pseudoephedrine.
They cover both symptom groups — but they carry all the decongestant cautions. A hypertensive
patient who was safely taking plain loratadine is not safe on the "-D" version.
🧠 The "D" stands for decongestant — and for "don't, if they're hypertensive".
😤
PART 3 · COUGH DRUGS
STOP IT OR HELP IT
First decide whether this cough is doing a job. Everything follows from that one question.
Two drugs, two completely different places on the same loop.
An antitussive interrupts the signal. An expectorant changes the cargo. They are not
interchangeable and they can be prescribed together.
⭐ The question that comes before the drug: is this cough productive?
DRY / non-productiveHacking, tickly, brings nothing up, keeps the patient
awake, hurts the chest and throat. The cough is doing no useful work → suppress it.
WET / productiveRattly, loose, brings up sputum. The cough is clearing the
lungs → do NOT suppress it. Thin the mucus and let it work.
Suppressing a productive cough traps secretions — that is how
atelectasis and pneumonia start.
🧠 SUPPRESS a cough that does nothing. HELP a cough that is bringing something up.
💊 Antitussives — dextromethorphan
The "DM" in a cough-syrup name. It acts centrally, raising the threshold of the cough center
in the medulla so the same irritation no longer triggers a cough.
Non-opioid at normal doses; drowsiness and dizziness are the usual side effects. It is abused at
high doses, so many places keep it behind the counter — worth asking about in adolescents.
🧠 DM = "Doesn't Move" the mucus. It just turns the cough down.
🚨 Antitussives — codeine-containing
Codeine is an opioid. It suppresses the cough center well, and it carries every opioid problem
with it:
Respiratory depression — the reason it is not used in COPD and used very cautiously in
anyone with poor respiratory reserve.
Sedation — no driving, no alcohol, no other CNS depressants.
Constipation — the one opioid side effect that never fades. Fluids, fiber, and often a
stool softener from day one.
Orthostatic hypotension — change position slowly.
Dependence potential — short courses only.
Nausea — take it with food.
Contraindicated in children in most current guidance.
🧠 Codeine is an opioid wearing a cough-syrup label. Treat it like one.
🧠 The codeine teaching list — and the three traps
Teach: ① slow position changes ② not for COPD ③ take with food ④ increase fluids
⑤ at least 8 glasses of water a day.
Do NOT expect: photosensitivity · heart palpitations · insomnia or anxiety. Those three appear as
distractors constantly. Codeine sedates; it does not wind you up.
🧠 If an option sounds stimulating, it is not a codeine effect.
Notice what guaifenesin does not do — it does not stop
the cough and it does not fight infection. It changes the mucus so the machinery you already have can shift it.
💧 Expectorants — guaifenesin (Mucinex)
Thins and loosens secretions so that the cilia and the cough can move them. It makes a cough
more productive, not less.
Increase fluid intake — at least about 2 L a day (roughly 8 full glasses) unless fluids are
restricted. Water is part of the dose. Humidified air helps too.
It is asthma-safe.
🧠 Guaifenesin without water is a pill with no partner.
🚨 Acetylcysteine (Mucomyst) — the mucolytic with two faces
Face 1 — mucolytic: it breaks the bonds inside thick mucus so it can be suctioned or coughed out.
It smells strongly of rotten eggs, which makes patients gag — warn them.
Face 2 — antidote: acetylcysteine is the antidote for acetaminophen (Tylenol) overdose.
That is the fact most likely to be tested.
NOT SAFE in asthma — it can cause or worsen bronchospasm. Have a bronchodilator available
and monitor closely when it is given by inhalation.
🧠 Acetylcysteine → Antidote for Acetaminophen · and Avoid in
Asthma.
🎓 Cough teaching that isn't a drug
Fluids first — the cheapest and most effective mucolytic there is.
Humidifier, steamy shower, saline nebs if ordered.
Sit upright and use controlled coughing / huff coughing to clear secretions.
Honey (in patients over 1 year) soothes a dry throat; never honey under 1 year — botulism risk.
Stop smoking and avoid smoke exposure.
Report a cough lasting more than about 1 week, a fever, blood in the sputum, or shortness of breath.
🧠 Water, upright, humidity. Free, safe and it works.
🎯
PART 4 · PICK THE DRUG
EXAM
Read the symptom, name the job, then name the family. In that order.
Print this one. Every upper-respiratory drug question is
really asking you to walk one of these four rows from left to right.
🎯 TRAP 1 — the "requires further teaching" cough question
A client with a productive cough and thick secretions is prescribed guaifenesin. Which
statement by the client requires further teaching?
1
"I will drink about 8 glasses of water a day." —
correct; fluid is part of how the drug works.
2
"This will stop my cough so I can sleep." ✅
Needs correction. Guaifenesin is an expectorant, not a suppressant — it makes the cough
more productive.
3
"I'll use a humidifier at night." — correct.
4
"I'll call if the cough lasts more than a week." —
correct.
The confusion to kill: "cough medicine" is not one thing. Expectorant = help the
cough. Antitussive = stop the cough. A question that pairs the wrong verb with the right drug is the
commonest version of this item.
🎯 TRAP 2 — which client should not get this decongestant?
The nurse reviews a request for an over-the-counter oral pseudoephedrine product. Which
client should the nurse advise against it?
1
A 68-year-old with uncontrolled hypertension ✅ —
an alpha agonist constricts vessels systemically and raises blood pressure.
2
A 24-year-old with seasonal allergies and no other
history.
3
A 30-year-old with a mild sinus headache.
4
A 40-year-old with a cold and no chronic conditions.
The trigger words: hypertension, heart disease, dysrhythmia, hyperthyroidism,
glaucoma, diabetes, BPH. Any of those next to a decongestant = the answer. Note that the same client
could safely take plain loratadine — it is the decongestant, not the antihistamine, that is the
problem.
🎯 TRAP 3 — the codeine distractors
A client is prescribed a codeine-containing cough syrup. Which side effects should the
nurse teach the client to expect? Select all that apply.
A
Drowsiness ✅
B
Constipation ✅
C
Dizziness on standing ✅ — change position slowly.
D
Photosensitivity ❌ — not a codeine effect.
E
Insomnia and anxiety ❌ — the opposite; codeine sedates.
F
Heart palpitations ❌ — that belongs to
decongestants and beta-2 agonists.
Sort every option into "up" or "down". Codeine is a downer: sedation, slowed
breathing, slowed gut, lowered blood pressure. Any option that speeds something up is wrong.
🎯 TRAP 4 — the asthma-safety question
Which of these is safe to give a client with asthma who has thick secretions?
1
Guaifenesin ✅ — asthma-safe expectorant.
2
Inhaled acetylcysteine ❌ — can cause or worsen
bronchospasm.
3
Naproxen for the associated headache ❌ —
NSAIDs can trigger bronchospasm in a subset of asthmatics.
4
Propranolol ❌ — a non-selective beta blocker;
directly opposes bronchodilation.
Keep an "asthma no-fly list" in your head: non-selective beta blockers, NSAIDs and
aspirin, and inhaled acetylcysteine. Guaifenesin is the safe one and it is worth remembering by name.
⭐ The one-line summary of the whole page
Itch/sneeze/drip → antihistamine. 1st gen sedates, 2nd gen doesn't.
🧠 Upper airway = this page. Lower airway = NG-102 and NG-143.
🤧 1st GEN SEDATESDiphenhydramine crosses into the brain and is
an anticholinergic: dry, blurred, retained, constipated, confused. Avoid in older adults.
🚨 SPRAY = 3 DAYS MAXBeyond that you get rebound congestion
— a nose more blocked than when you started. Saline instead.
🚨 DECONGESTANT ≠ JUST THE NOSEIt constricts everywhere. Question
it in hypertension, heart disease, hyperthyroidism, glaucoma, BPH.
😤 DRY vs WETSuppress a cough that does nothing. Never
suppress a productive one — trapped secretions become pneumonia.
💧 GUAIFENESIN + WATERAt least 2 L/day
(~8 glasses) unless restricted. Asthma-safe. It doesn't stop the cough — it makes it work.
🧪 ACETYLCYSTEINEAntidote for acetaminophen overdose ·
smells like rotten eggs · avoid in asthma (bronchospasm).