Vasopressin
Vasopressin, a peptide. Posterior-pituitary peptide differing from oxytocin by two residues (Phe-3 + Arg-8 vs Ile-3 + Leu-8). Activates V1a… IV half-life 0.4 h.
Posterior-pituitary peptide differing from oxytocin by two residues (Phe-3 + Arg-8 vs Ile-3 + Leu-8). Activates V1a (vascular smooth muscle → vasoconstriction), V1b (pituitary → ACTH release), and V2 (renal collecting-duct → aquaporin-2 insertion → antidiuresis). Rapidly inactivated by peptidases — IV infusion required for vasopressor use.
PK: Baumann 1976 (PMID:1262458), 10 hydrated normal subjects, IV radioiodinated tracer, verbatim "the mean plasma half-life 24.1 min" = 0.4 h. The half-life stands as stored. V 14 L dropped 2026-09-06: the abstract gives only the qualitative "rapidly distributed into a space approximating the extracellular fluid volume", so 14 L was an inference from that phrase rather than a cited value, and no human numeric volume for vasopressin appears in any indexed abstract. CAVEAT: this is a tracer study at physiological concentrations, not vasopressor dosing, and clearance is infusion-rate dependent in dog (PMID:216270).
Pharmacokinetics
- IV — t½ 24 min
Sources: PMID:1262458