USMLE STEP 1 Pharmacology 2022 Complete Solution guide.

USMLE STEP 1 Pharmacology 2022
Complete Solution guide.
What are the major functions of the α1 receptor?
✅- Increase vascular smooth muscle contraction, increase pupillary dilator muscle contraction
(mydriasis), increase intestinal and bladder sphincter muscle contraction

What are the major functions of the α2 receptor?
✅- Decrease sympathetic outflow, decrease insulin release, decrease lipolysis, increase platelet
aggregation, decrease aqueous humor production

What are the major functions of the β1 receptor?
✅- Increase heart rate, increase contractility, increase renin release, increase lipolysis

What are the major functions of the β2 receptor?
✅- Vasodilation, bronchodilation, increase lipolysis, increase insulin release, decrease uterine
tone (tocolysis), ciliary muscle relaxation, increase aqueous humor production

What are the major functions of the M1 receptor?
✅- CNS, enteric nervous system

What are the major functions of the M2 receptor?
✅- Decrease heart rate and contractility of atria

What are the major functions of the M3 receptor?
✅- Increase exocrine gland secretions (e.g., lacrimal, salivary, gastric acid), increase gut
peristalsis, increase bladder contraction, increase bronchoconstriction, pupillary sphincter muscle
contraction (miosis), ciliary muscle contraction (accommodation)

What are the major functions of the D1 receptor?
✅- Relaxes renal vascular smooth muscle

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.