Drug Mnemonic

Vasopressin

Antidiuretics • V1 = vasoconstriction • v2 = Water Reabsorption
April 13, 2026

A story built from the name vasopressin itself - so the mechanism of action, key side effects, and the way Step 1 actually tests it stick on the first read.

RxMnemonic Antidiuretics
Vasopressin
Antidiuretics • V1 = vasoconstriction • v2 = Water Reabsorption
VASO = vessel + PRESSIN = pressing
Separate vasopressin into VASO (sounds like vessel) and PRESSIN (sounds like pressing). Now imagine a hand pressing (PRESSIN) on a blood vessel (VASO), reminding you of vasoconstriction. At the same time, imagine a hand pressing (PRESSIN) on the collecting duct, stopping water flow, like how vasopressin stops water from leaving the body via urine.
Vasopressin pharmacology mnemonic illustration
V1 & V2 agonist VASO = vessel | PRESSIN = pressing
HOW STEP TESTS IT
1
Causes vasoconstriction via V1 receptors on vascular smooth muscle, which is why it helps in esophageal variceal bleeding and vasodilatory shock.
2
Increases water reabsorption via V2 receptors in the collecting duct by increasing aquaporin insertion, so it can treat central diabetes insipidus, but can cause hyponatremia/water intoxication.
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Practice Question

Which adverse effect is most classically associated with excessive V2-mediated action of vasopressin?

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Pharmacology Summary

Vasopressin: Mechanism, Uses & High-Yield Facts for USMLE Step 1

Vasopressin (ADH) acts on two receptor subtypes with distinct effects. V1 receptors on vascular smooth muscle cause vasoconstriction, making vasopressin useful in vasodilatory shock and esophageal variceal bleeding. V2 receptors in the collecting duct increase aquaporin-2 insertion, concentrating urine — this is the basis for treating central diabetes insipidus. Excess V2 activity leads to water retention, hyponatremia, and water intoxication.

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