Pharmacology confusion pairs
54 Pharmacology topics students commonly mix up on Step 1, each with the fastest separator, a side-by-side comparison, and a free practice question.
- Serotonin syndrome vs Neuroleptic malignant syndromeSerotonin syndrome: hours, clonus and hyperreflexia. NMS: days, lead-pipe rigidity.Video
- Antimuscarinic toxidrome vs Sympathomimetic toxidromeAntimuscarinic: dry skin with quiet bowel sounds; sympathomimetic: diaphoretic skin with preserved or hyperactive bowel sounds.Video
- Methanol overdose vs Ethylene glycol overdoseMethanol: visual loss from optic injury; ethylene glycol: acute kidney injury with calcium oxalate crystalluria.Video
- ACE inhibitors vs Angiotensin receptor blockersACE inhibitors raise bradykinin; ARBs block the receptor without the same bradykinin cough signal.Video
- Beta-1 selective blockers vs Nonselective beta blockersBeta-1 selective blockers are heart/renin focused; nonselective blockers add beta-2 lung and metabolic effects.Video
- Dihydropyridine calcium channel blockers vs Non-dihydropyridine calcium channel blockersDihydropyridines (-dipine): vascular, cause edema and reflex tachycardia; non-dihydropyridines (verapamil, diltiazem): cardiac, slow the…
- Loop diuretics vs Thiazide and potassium-sparing diureticsLoop means NKCC2, strong diuresis, calcium wasting, ototoxicity; thiazide means calcium retention; potassium-sparing means hyperkalemia.Video
- Class I antiarrhythmics vs Classes II, III, and IV antiarrhythmicsClass I block sodium channels; class II are beta blockers, class III block potassium channels, class IV block AV-node calcium channels.
- Class IA sodium-channel blockers vs Class IB and IC sodium-channel blockersIA prolongs action potential/QT; IB shortens action potential; IC strongly slows conduction and widens QRS.
- Heparin vs Warfarin and direct oral anticoagulantsHeparin is immediate antithrombin/PTT; warfarin is vitamin K/PT-INR; direct oral agents are factor Xa or thrombin without routine INR.Video
- Aspirin vs P2Y12 inhibitorsAspirin: irreversibly blocks platelet COX-1 and thromboxane A2; P2Y12 inhibitors (clopidogrel, ticagrelor): block the platelet ADP receptor.
- tPA derivatives vs StreptokinasetPA is recombinant and relatively fibrin-specific; streptokinase is antigenic and more systemic.
- Statins vs Non-statin lipid drugsStatins block cholesterol synthesis; non-statins are sorted by triglycerides, absorption, bile binding, VLDL, or LDL receptor recycling.Video
- Metformin and insulin sensitizers vs Insulin secretagogues, incretin drugs, and SGLT2 inhibitorsMetformin lowers liver glucose output; sulfonylureas force insulin; incretin drugs are glucose-dependent; SGLT2 drugs spill glucose into…
- Prandial insulin vs Basal insulinPrandial insulin covers meals or acute correction; basal insulin covers fasting/background needs.
- COX-1 inhibition vs COX-2 selective inhibitionCOX-1 is stomach/platelet protection; COX-2 is inflammation-focused with thrombotic tradeoff when selectively blocked.
- SSRIs and SNRIs vs TCAs, MAOIs, and atypical antidepressantsSSRI/SNRI questions center on reuptake and tolerability; TCA/MAOI questions center on toxicity and interactions.Video
- Typical antipsychotics vs Atypical antipsychoticsTypical means more EPS/prolactin from strong D2 blockade; atypical means more metabolic risk with serotonin-D2 profile.
- First-generation antihistamines vs Second-generation antihistaminesFirst generation crosses into brain and is anticholinergic; second generation is more peripheral and cleaner.
- Benzodiazepines vs Barbiturates and Z-drugsBenzodiazepines increase frequency; barbiturates increase duration; Z-drugs are insomnia-focused benzodiazepine-site drugs.
- Full opioid agonists vs Partial agonists and antagonistsFull agonists maximally activate mu receptors; partial agonists cap activation; antagonists block activation.
- Penicillins vs Cephalosporins and carbapenemsPenicillins are named by penicillin family; cephalosporins are generation-sorted; carbapenems are broad severe-infection beta-lactams.Video
- Early-generation cephalosporins vs Later-generation cephalosporinsEarly generations are skin/gram-positive focused; later generations add gram-negative, Pseudomonas, or MRSA anchors.
- Macrolides and tetracyclines vs AminoglycosidesMacrolides are 50S/QT; tetracyclines are 30S/teeth-photosensitivity; aminoglycosides are 30S bactericidal with oto-nephrotoxicity.
- Fluoroquinolones vs SulfonamidesFluoroquinolones: block DNA gyrase, risk tendon rupture and QT prolongation; sulfonamides: block folate synthesis, risk SJS and…Video
- Vancomycin vs Linezolid and daptomycinVancomycin is wall plus infusion/renal; linezolid is 50S plus marrow/serotonin; daptomycin is membrane plus CK/no pneumonia.
- Acyclovir vs Ganciclovir and foscarnetAcyclovir is HSV/VZV plus viral TK; ganciclovir is CMV plus marrow; foscarnet is resistant CMV/HSV plus renal-electrolyte toxicity.
- Oseltamivir vs Amantadine and ribavirinOseltamivir is neuraminidase/influenza A and B; amantadine is M2/influenza A but resistance-limited; ribavirin is hemolytic-teratogenic…
- Reverse transcriptase inhibitors vs Protease, integrase, and entry inhibitorsNRTI/NNRTI act at reverse transcription; protease acts at maturation; integrase acts at integration; entry drugs act before cell infection.
- Azoles vs Echinocandins and polyenesAzoles make less ergosterol; echinocandins weaken the wall; polyenes punch membrane pores by binding ergosterol.
- Primaquine vs Chloroquine, mefloquine, and atovaquone-proguanilPrimaquine clears dormant liver forms; the others mainly cover blood-stage treatment or prophylaxis lanes.
- Isoniazid and rifampin vs Pyrazinamide and ethambutolINH equals B6 neuropathy; rifampin equals orange/CYP; pyrazinamide equals uric acid; ethambutol equals eyes.
- Methotrexate vs 5-fluorouracil and capecitabineMethotrexate blocks DHFR and uses leucovorin rescue; 5-FU/capecitabine block thymidylate synthase and leucovorin strengthens 5-FU binding.
- Cisplatin vs Carboplatin and oxaliplatinCisplatin equals kidney/ear; carboplatin equals marrow; oxaliplatin equals cold neuropathy.
- Tamoxifen and raloxifene vs Aromatase inhibitorsSERMs (tamoxifen, raloxifene): bind the estrogen receptor and can protect bone; aromatase inhibitors: block estrogen synthesis and worsen…
- Bisphosphonates and denosumab vs TeriparatideBisphosphonates/denosumab reduce osteoclast resorption; teriparatide builds bone through intermittent PTH signaling.
- Levothyroxine and liothyronine vs PTU and methimazoleLevothyroxine/liothyronine add thyroid hormone; PTU/methimazole stop thyroid hormone production.
- Propylthiouracil vs MethimazolePTU first trimester or thyroid storm; methimazole usual nonpregnant default after early pregnancy risk window.
- Bromocriptine vs CabergolineBoth lower prolactin through D2 agonism; bromocriptine is shorter and pregnancy-familiar, cabergoline is longer and usually better…
- Octreotide and lanreotide vs Dopamine agonistsSomatostatin analogs (octreotide): suppress GH and GI hormones; dopamine agonists (cabergoline, bromocriptine): suppress prolactin.
- Naloxone vs NaltrexoneNaloxone: short-acting antagonist for acute overdose rescue; naltrexone: long-acting antagonist for maintenance after detox.Video
- Flumazenil vs NaloxoneFlumazenil reverses benzodiazepine sedation but can cause seizures; naloxone reverses opioid respiratory depression.
- N-acetylcysteine vs FomepizoleNAC restores glutathione for acetaminophen; fomepizole blocks alcohol dehydrogenase for toxic alcohols.
- Cholinergic excess vs Anticholinergic toxicityCholinergic excess: wet toxidrome with miosis (SLUDGE-M); anticholinergic toxicity: dry toxidrome with mydriasis and ileus.Video
- Atropine vs PralidoximeAtropine blocks muscarinic receptors; pralidoxime restores the enzyme and helps nicotinic toxicity if early.
- Phase I metabolism vs Phase II metabolismPhase I modifies by oxidation/reduction/hydrolysis, often CYP-mediated; Phase II conjugates with…
- First-order kinetics vs Zero-order kineticsFirst-order: a constant fraction cleared per unit time, constant half-life; zero-order: a constant amount cleared, half-life rises with…
- Low volume of distribution vs High volume of distributionLow volume of distribution: drug stays in plasma (heparin, warfarin); high volume of distribution: drug binds widely to tissue…
- Competitive inhibition vs Noncompetitive inhibitionCompetitive inhibition increases apparent Km with unchanged Vmax; noncompetitive inhibition decreases Vmax because substrate cannot…
- Agonists and partial agonists vs Antagonists and inverse agonistsAgonists activate, partial agonists activate less, antagonists block, inverse agonists push below baseline.
- Acetaminophen overdose vs Aspirin overdoseAcetaminophen is delayed hepatic necrosis treated with NAC; aspirin is tinnitus plus mixed respiratory alkalosis/anion-gap metabolic…
- Ethylene glycol and methanol poisoning vs Isopropyl alcohol poisoningEthylene glycol = kidney/oxalate acidosis; methanol = eye/formate acidosis; isopropyl = ketosis without anion-gap acidosis.
- Cyanide poisoning vs Carbon monoxide poisoningCyanide is complex IV blockade with severe lactic acidosis/shock; CO is carboxyhemoglobin with normal PaO2, low oxygen content, left…
- Lead poisoning vs Mercury poisoningLead is abdominal pain plus heme-synthesis anemia/basophilic stippling; mercury is tremor, neuropsychiatric change, sensory loss, and…