What is the half-life of oxytocin?

Half-Life of Oxytocin

The half-life of oxytocin is approximately 3-5 minutes when administered intravenously.

Pharmacokinetics of Oxytocin

Oxytocin is a peptide hormone that plays a crucial role in reproductive physiology, particularly during labor and delivery. Understanding its half-life is essential for appropriate clinical use and dosing.

Intravenous Administration

• The median half-life of oxytocin after intravenous administration is 3.2 minutes (range: 2.0-5.7 minutes) following a single injection 1
• When administered as a continuous infusion, the half-life increases slightly to approximately 4.8 minutes (range: 4.4-6.1 minutes) 1
• The clearance of oxytocin is approximately 1.5 L/min, which is higher than that of related peptides like vasopressin 1

Distribution and Metabolism

• Oxytocin has an apparent volume of distribution of about two-thirds of the extracellular volume 1
• Unlike vasopressin, oxytocin is not significantly bound to plasma proteins, with studies showing it to be completely unbound in human plasma 1
• Oxytocin is primarily eliminated through renal and hepatic mechanisms

Stability

• Oxytocin demonstrates relatively good stability in plasma compared to other neurohypophysial hormones
• At 4°C, there is no significant loss of oxytocin activity for up to 7 days 1
• At body temperature (37°C), oxytocin shows a 20% loss after 24 hours and a 50% loss after 48 hours 1

Clinical Implications

The short half-life of oxytocin has important implications for its clinical use:

• Rapid onset of action (1-2 minutes) after IV administration 2
• Duration of effect is typically 30-60 minutes after a single dose 2
• When used for labor induction or augmentation, oxytocin is typically administered as a continuous infusion to maintain steady plasma levels
• Due to its short half-life, the effects of oxytocin quickly diminish after discontinuation of infusion
• Careful titration is required to achieve and maintain adequate uterine contractions while avoiding complications

Administration Considerations

• Initial doses of oxytocin for labor induction typically range from 1-3 mIU/min with gradual increases 3
• Maximum rates may reach up to 36 mIU/min, titrated at 15-40 minute intervals 3
• The total amount administered during labor typically ranges from 5-10 IU 3
• Plasma concentration increases in a dose-dependent manner, with infusion rates of 20-30 mIU/min increasing plasma levels approximately 2-3 fold above baseline 3

The short half-life of oxytocin necessitates continuous infusion for sustained effect during labor management, but also provides a safety advantage as any adverse effects will rapidly resolve upon discontinuation of the infusion.