Oxytocin

 

 

Uses

Used during delivery

IV oxytocin is effective within 30-60 seconds

IM oxytocin is effective in 3-4 minutes.

Its duration of action is 5-15 mins.

 

 

Treatment of Post-partum hemorrhage

Prophylaxis in the 3rd stage of labour has demonstrated a significant reduction in blood loss >500ml and in the need for therapeutic oxytocin (RR 0.5 for each) Cochrane Review, 2001

 

Augmentation of labour is controversial; some say high dose, some say low dose, and others say none at all. It is, as of 2009, the only drug approved for augmentation of labour. It appears to reduce the duration of labour somewhat but does not reduce the risk of C-section.

 

Induction of labour is another use for oxytocin, in which prostaglandin PGE2 may also be used.

SOGC Clinical Practice Guideline 2001 suggests we use the minimum dose to achieve active labour, that dose intervals are no less that 30 min, and that reassessment is reasonable once a dose of 20 mU/ml is reached.

ACOG Practice Bullitin 10 1999 (2006) supports both low and high dose protocols.

RCOG (NICE guidelines) 2008 - IV oxytocin alone should not be used for induction of labour. Amniotomy and oxytocin should not be used as a primary method unless there are specific contraindications to the use of PGE2. This is due to its increased invasiveness, increased discomfort, and increased risk of uterine hyperstimulation

 

 

 

Mechanism

 

 

 

Dose and Half Life

Physiologic and pharmacotherapeutic half life is on the order of minutes.

 

 

 

Side Effects

SE are dose-related

hyperstimulation

fetal heart decel

hyponatremia occurs really only after dose of 40 mIU/min

 

 

 

Contraindications and Drug Interactions

 

 

 

 

Metabolism and Excretion