Terlipressin

Terlipressin (via its active metabolite Lys8-vasopressin) binds V1a receptors on vascular smooth muscle, particularly in the splanchnic circulation. V1a couples through Gq to activate PLC-beta, generating IP3/DAG and releasing intracellular Ca2+, causing smooth muscle contraction. Splanchnic vasoconstriction reduces blood flow to the portal venous system, decreasing portal pressure and collateral flow through gastroesophageal varices. Systemic vasoconstriction also occurs, increasing mean arterial pressure.

HRS-1 occurs when extreme splanchnic vasodilation in cirrhosis reduces effective arterial blood volume, triggering intense renal vasoconstriction via the renin-angiotensin-aldosterone system and sympathetic nervous system. Terlipressin reverses this by constricting the splanchnic bed (increasing effective blood volume), which reflexively reduces renal vasoconstriction and restores renal perfusion. Combined with albumin infusion (which expands plasma volume), terlipressin achieves reversal of HRS-1 in ~32-34% of patients in clinical trials.

The triglycine prodrug design converts terlipressin from a very short-acting compound into one with 4-6 hour dosing intervals. After IV bolus, terlipressin is cleaved to lysine-vasopressin over 30-60 minutes, avoiding the severe initial cardiovascular side effects of direct vasopressin bolus. This gradual conversion mimics continuous infusion kinetics while allowing simple intermittent bolus dosing. The prodrug strategy was a key pharmacological innovation enabling practical clinical use.

The CONFIRM trial (Phase III, n=300) showed terlipressin + albumin achieved HRS-1 reversal (serum creatinine <1.5 mg/dL) in 32% vs 17% placebo. Dialysis-free survival and transplant-free survival improved. The FDA approved terlipressin (Terlivaz) in 2022, providing the first approved pharmacotherapy for HRS-1 in the US. European guidelines had already recommended terlipressin as first-line for HRS since the 2000s.

Terlipressin is first-line pharmacotherapy for acute esophageal variceal bleeding in Europe, Asia, and most non-US markets. Meta-analyses demonstrate superior efficacy over placebo and comparability to somatostatin/octreotide for bleeding control, with a proven mortality benefit in meta-analyses (the only vasoactive drug showing mortality benefit in variceal bleeding). It reduces rebleeding and is combined with endoscopic band ligation as standard care.

In vasodilatory septic shock, vasopressin and its analogues including terlipressin have been studied as catecholamine-sparing agents. The TERLIVAZ and other trials evaluated terlipressin in septic shock, showing vasopressor-sparing effects and maintained MAP without improved 28-day mortality. Terlipressin reduces norepinephrine requirements in septic shock but is not currently guideline-recommended as first-line vasopressor.