Substrate for nitric oxide synthesis NOS → endothelial NO → vasodilation. Intermediate in the urea cycle. Precursor to creatine (with glycine and methionine), polyamines (via ornithine), and proline. Oral F limited by saturable CAT-1 transport and first-pass hepatic arginase activity.
Half-Life (t½)
PO: 1.7h, IV: 1.7h
Dosing Guidelines
PO: Typical 4 g (Range: 3–6 g)
IV: Typical 4 g (Range: 3–6 g)
Target Organ Systems
cardiovascular
digestive
Interactions
Lysine (caution): Arg and Lys compete for CAT-1 uptake; high-dose Arg promotes HSV reactivation whereas Lys suppresses it — opposing effects on herpes recurrence.
Agmatine (synergistic): Direct precursor via arginine decarboxylase.
Citrulline (synergistic): Citrulline bypasses arginase first-pass metabolism and is recycled to arginine — yielding higher and more sustained plasma arginine than oral arginine itself.
Pathways It Modulates
Urea cycle (substrate) — urea cycle + NO precursor