Oxytocics

Oxytocics are agents which increase the force of uterine contraction.

Property Oxytocin Ergometrine PGF (Dinoprost) Carboprost
Class Endogenous (typically synthetic version used) posterior pituitary hormone Ergot alkaloid Prostaglandin
Uses Augmentation of labour, increase uterine tone (PPH) PPH Severe PPH Severe PPH
Presentation Clear liquid at 5-10 U.ml-1 Clear liquid at 250μg.ml-1, up to 8 doses (2mg)
Route of Administration IV IV, IM Intramyometrial injection, IM Intramyometrial, IM
Dosing 1.5-12mU.min-1 250μg IM (IV in emergency via slow push) 500μg IM
Metabolism Oxytocinases in liver and kidney
Mechanism of Action Oxytocin GPCR in the uterus, increase Ca2+ influx. Structurally similar to ADH. Acts on α and 5HT2 receptors on uterine and vascular smooth muscle
Resp Bronchospasm (may be severe) Bronchospasm (severe if IV so this route is contraindicated) Bronchospasm, APO due to ↑ PVR with subsequent hypoxia
CVS HR, ↓ BP following boluses SVR, ↑ BP (may cause, ↓ HR) coronary vasoconstriction SVR, ↑ BP SVR, ↑ BP (usually transient)
CNS Headache, nausea, vomiting Headache, nausea Nausea, vomiting Headache
Renal ↓ UO due to ADH-like effects with prolonged infusions
GU ↑ Uterine tone (↑ frequency at low dose, tetanic contraction at high dose), foetal distress, lactation ↑ Uterine contraction frequency and tone ↑ Uterine contraction frequency and tone ↑ Uterine contraction frequency and tone, contraindicated in pelvic inflammatory disease
Other May be metabolised by oxytocinases in blood products if coadministered on the same line Contraindicated in pre-eclampsia due to HTN Deprecated by carboprost, increased body temperature

References

  1. Peck TE, Hill SA. Pharmacology for Anaesthesia and Intensive Care. 4th Ed. Cambridge University Press. 2014.
  2. Petkov V. Essential Pharmacology For The ANZCA Primary Examination. Vesselin Petkov. 2012.
  3. Smith S, Scarth E, Sasada M. Drugs in Anaesthesia and Intensive Care. 4th Ed. Oxford University Press. 2011.
  4. Royal Women's Hospita. Postpartum Haemorrhage - Carboprost. 2017.
Last updated 2019-02-19

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