EpistemisCarbetocin
Carbetocin (e.g. *Pabal*).
Mechanism
Mechanism of Action
Carbetocin is a long-acting synthetic analogue of oxytocin. It is a selective agonist of the OXTR receptor in the uterine myometrium. Structurally, it differs from oxytocin by the deamination of the amino terminal end of the cysteine and the replacement of the disulfide bridge by a thioether bond, chemical modifications that confer intrinsic resistance to degradation by maternal aminopeptidases and oxytokinases.
Pharmacokinetics
Pharmacokinetics
- Routes of administration: Intravenous (slow bolus administered over a period of no less than 1 minute) or deep intramuscular.
- Bioavailability (F): Does not apply to the IV route; after IM administration it is approx. 80%.
- Distribution: Modest distribution volume. It exhibits rapid tissue clearance kinetics. The maximum plasma concentration after IM administration is reached in about 30 minutes.
- Metabolism: It undergoes enzymatic clearance significantly slower than oxytocin. It is not degraded by circulating placental oxytokinases, which explains its prolonged pharmacodynamic stability.
- Half-life (t1/2): Approximately 40 minutes (almost 10 times longer than that of natural oxytocin).
- Duration of effect: A single dose of carbetocin maintains continuous, rhythmic uterotonic activity for approximately 1 to 2 hours after IV administration, and even longer IM.
Indicators and dose
Indications
- Prevention of uterine atony and postpartum hemorrhage in women undergoing elective cesarean section under epidural or spinal anesthesia.
- Prevention of PPH after vaginal delivery with risk factors for uterine atony.
Precision Dosing
Caesarean section or Vaginal delivery: A single dose of 100 µg (1 mL) administered slowly intravenously over a minimum of 60 seconds, or by deep intramuscular injection, performed immediately after delivery of the fetus (and preferably before manual removal of the placenta).
Pregnancy and Breastfeeding
Contraindicated before birth. Compatible with breastfeeding; Small amounts of the drug are excreted in milk, but are degraded in the infant's digestive tract without exerting measurable biological effects.
Security
Contraindications
- Known hypersensitivity to carbetocin or oxytocin.
- It should not be used for induction or conduction of labor, nor before complete delivery of the fetus.
- Severe liver or kidney failure.
- Severe cardiovascular disease or history of coronary heart disease.
- Active neurological disorders (such as uncontrolled epilepsy).
Adverse Effects (ADR)
| System | Adverse Effect | Mechanism / Occurrence |
|---|---|---|
| Vascular | Hypotension and facial flushing | Transient vasodilation mediated by nitric oxide. More pronounced after fast bowling IV. |
| Gastrointestinal | Nausea, vomiting and abdominal pain | Direct spasmogenic effect of the drug on gastric smooth muscle receptors. |
| Nervous System | Headache and Tremor | Moderate incidence (5-10%), transient and self-limited. |
| Metabolic | Mild hyponatremia | Marginal water retention due to binding to renal vasopressin receptors (much smaller effect than oxytocin per single dose). |
Interactions
Potentiation of the risk of vasoconstriction and severe hypertensive crises if co-administered with ergot alkaloids (ergometrine) or sympathomimetics (adrenaline, ephedrine). It should not be combined with oxytocin in the same line or infusion simultaneously.
Epistemis is educational review material. It is not a medical device, does not diagnose or prescribe treatment, and does not replace formal medical training, current clinical guidelines, or professional clinical judgment.
- System
- Gynecology and Obstetrics
- Cluster
- Uterotonics