Pharmacology · USMLE Step 1

USMLE Pharmacology: Drug Classes and Mechanisms II

High-yield drug classes (second half: GI, renal, endocrine, respiratory, antineoplastic) with mechanism of action, one card per class or key drug.

48 cards · basic cards · AI-written, checked twice. Edit anything.

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How do proton pump inhibitors reduce gastric acid?
Irreversible inhibition of the H+/K+-ATPase pump on parietal cells
Mechanism of action of H2 receptor antagonists (e.g., ranitidine, famotidine)
Competitive antagonism of histamine H2 receptors on parietal cells
How does sucralfate protect against peptic ulcers?
Forms a protective barrier coating over the ulcer base by binding to ulcer crater proteins
Metoclopramide increases gastric emptying by which mechanism?
D2 dopamine receptor antagonism; increases acetylcholine effect on smooth muscle
Ondansetron's primary mechanism for preventing nausea and vomiting
5-HT3 serotonin receptor antagonism in the chemoreceptor trigger zone and GI tract
How does loperamide reduce diarrhea?
Mu opioid receptor agonist that increases intestinal muscle tone and reduces propulsive contractions
Bismuth subsalicylate reduces diarrhea by which mechanism?
Antimicrobial activity and anti-inflammatory effects on the intestinal mucosa
Mesalamine (5-ASA) mechanism in inflammatory bowel disease
Local anti-inflammatory action on GI mucosa; inhibits NF-kappa-B and reduces TNF-alpha production
Antacids reduce gastric acid by what mechanism?
Direct chemical neutralization of gastric acid (HCl) via bases like CaCO3, MgOH, Al(OH)3
Why is omeprazole more effective than H2 blockers at controlling acid?
Irreversible H+/K+-ATPase inhibition (vs. competitive antagonism) produces near-complete acid suppression
Loop diuretics increase urine volume by inhibiting which transporter?
Na+/K+/2Cl- cotransporter (NKCC2) in the thick ascending limb of the loop of Henle
Thiazide diuretics inhibit which renal transporter?
Na+/Cl- cotransporter (NCC) in the distal convoluted tubule
Potassium-sparing diuretics work by which two main mechanisms?
ENaC channel blockers (amiloride, triamterene) or aldosterone antagonists (spironolactone)
How do osmotic diuretics increase urine output?
Increase plasma osmolarity, drawing water into the blood, then filtered by the glomerulus but not reabsorbed in the tubule
ACE inhibitors reduce blood pressure by inhibiting which enzyme?
Angiotensin-converting enzyme (ACE), blocking formation of angiotensin II from angiotensin I

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