USMLE STEP 1 PHARMACOLOGY COMPLETE HIGH-YIELD STUDY GUIDE WITH DRUG MECHANISMS AND NOTES

USMLE STEP 1 PHARMACOLOGY
COMPLETE HIGH-YIELD REVIEW GUIDE
WITH DRUGS AND MECHANISMS
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Updated 2026 Questions and Answers

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,What are the major functions of the D2 receptor? Modulates transmitter release, especially in the brain


What are the major functions of the H1 receptor? Increase nasal and bronchial mucus production, increase vascular permeability,
contraction of bronchioles, pruritis, pain


What are the major functions of the H2 receptor? Increase gastric acid secretion


What are the major functions of the V1 receptor? Increase vascular smooth muscle contraction




What are the major functions of the V2 receptor? Increase H2O permeability and reabsorption in collecting tubules of kidney (V2 is
found in the "2" kidneys)


What receptors are associate with Gq? H1, α1, V1, M1, and M3


What receptors are associated with Gs? H2, B1, B2, V2, D1


What receptors are associated with Gi? M2, α2, D2


Bethanechol -Direct cholinergic agonist
-Activates bowel and bladder smooth muscle
-Used in postoperative and neurogenic ileus
-Resistant to AChE


Carbachol -Direct cholinergic agonist
-Carbon copy of acetylcholine
-Constricts pupils and relieves intraocular pressure in glaucoma


Methacholine -Direct cholinergic agonist
-Stimulates muscarinic receptors in airways when inhaled
-Used as a challenge test for diagnosis of asthma


Pilocarpine -Direct cholinergic agonist
-Contracts ciliary muscle of eye (open angle glaucoma), contracts pupillary
sphincter (closed angle glaucoma)
-Potent stimulator of sweat, tears and saliva
-AChE resistant


Donepezil -Anticholinesterse - increases ACh
-Alzheimer disease




Galantamine -Anticholinesterse - increases ACh
-Alzheimer disease

,Rivastigmine -Anticholinesterse - increases ACh
-Alzheimer disease


Edrophonium -Anticholinesterse - increases ACh
-Historically used to diagnose myasthenia gravis (MG is now diagnosed by anti-
AChR Ab test.


Neostigmine -Anticholinesterse - increases ACh
-Used in postoperative and neurogenic ileus and urinary retention, myasthenia
gravis, and postoperative reversal of neuromuscular junction blockade


Physostigmine -Anticholinesterse - increases ACh
-Used in anticholinergic toxicity
-Crosses the blood-brain barrier (CNS)


Pyridostigmine -Anticholinesterse - increases ACh
-Increases muscle strength
-Used in myasthenia gravis (long acting)
-Does not penetrate CNS


Atropine -Muscarinic antagonist
-Used in bradycardia and for ophthalmic applications
-Also used as antidote for cholinesterase inhibitor poisoning
-Actions include increase pupil dilation, cycloplegia, decreased airway secretions,
decreased acid secretions, decreased gut motility, decreased bladder urgency in
cystitis
-Toxicity: increased body temp (due to decreased sweating), rapid pulse, dry
mouth, dry and flushed skin, cycloplegia, constipation, disorientation;
-Can cause acute angle-closure glaucoma in elderly (due to mydriasis), urinary
retention in men with prostatic hyperplasia, and hyperthermia in infants
-See also homatropine and tropicamide


Benztropine -Muscarinic antagonist
-Works in CNS
-Used in Parkinson disease and acute dystonia


Glycopyrrolate -Muscarinic antagonist
-Parental use: preoperative use to reduce airway secretions
-Oral use: drooling, peptic ulcer




Hyoscyamine -Muscarinic antagonist
-Antispasmodics for IBS


Dicyclomide -Muscarinic antagonist
-Antispasmodics for IBS


Ipratropium -Muscarinic antagonist
-Used in COPD and asthma

, Tiotropium -Muscarinic antagonist
-Used in COPD and asthma


Oxybutynin -Muscarinic antagonist
-Reduced bladder spasms and urge urinary incontinence


Solifenacin -Muscarinic antagonist
-Reduced bladder spasms and urge urinary incontinence


Tolterodine -Muscarinic antagonist
-Reduced bladder spasms and urge urinary incontinence


Scopalamine -Muscarinic antagonist
-Motion sickness


Tetrodotoxin -Poisoning can result from ingestion of poorly prepared puffer fish (exotic sushi)
-Highly potent toxin that binds fast voltage-gated Na+ channels in cardiac and
nerve tissue, preventing depolarization - blocks action potential without changing
resting potential (same mechanism as Lidocaine)
-Causes nausea, diarrhea, paresthesias, weakness, dizziness, loss of reflexes.
-Treatment is primarily supportive.




Ciguatoxin -Consumption of reef fish (e.g. barracuda, snapper, eel...)
-Causes ciguatera fish poisoning.
-Opens Na+ channels causing depolarization. Symptoms easily confused with
cholinergic poisoning.
-Temperature-related dysesthesia (e.g., "cold feels hot; hot feels cold") is
regarded as a specific finding of ciguatera.
-Treatment is primarily supportive.


Scombroid poisoning -Caused by consumption of dark-meat fish (e.g., bonito, mackerel, mahi-mahi,
tuna) improperly stored at warm temperature.
-Bacterial histidine decarboxylase converts histidine to histamine. Histamine is not
degraded by cooking.
-Acute-onset burning sensation of the mouth, flushing of face, erythema, urticaria,
pruritus, headache. May cause anaphylaxis-like presentation (i.e., bronchospasm,
angioedema, hypotension).
-Frequently misdiagnosed as allergy to fish.
-Treat supportively with antihistamines; if needed, antianaphylactics (e.g.,
bronchodilators, epinephrine).


Albuterol -β2 > β1 direct agonist
-Acute asthma


Salmterol -β2 > β1 direct agonist
-Long term asthma or COPD control