Oxytocics
Oxytocics are agents which increase the force of uterine contraction.
| Property | Oxytocin | Ergometrine | PGF2α (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 co-administered on the same line | Contraindicated in pre-eclampsia due to HTN | Deprecated by carboprost, increased body temperature |
References
- Peck TE, Hill SA. Pharmacology for Anaesthesia and Intensive Care. 4th Ed. Cambridge University Press. 2014.
- Petkov V. Essential Pharmacology For The ANZCA Primary Examination. Vesselin Petkov. 2012.
- Smith S, Scarth E, Sasada M. Drugs in Anaesthesia and Intensive Care. 4th Ed. Oxford University Press. 2011.
- Royal Women's Hospita. Postpartum Haemorrhage - Carboprost. 2017.