PITOCIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PITOCIN (PITOCIN).
Oxytocin receptor agonist; stimulates uterine smooth muscle contractions and myoepithelial cell contraction in the mammary gland.
| Metabolism | Primarily metabolized in the liver and kidneys by oxytocinase; also degraded in the gastrointestinal tract and by the lungs. |
| Excretion | Primarily renal: 90-95% of the dose is excreted in urine as intact peptide and metabolites; <1% excreted in feces via bile. |
| Half-life | Terminal elimination half-life is 3-5 minutes (plasma) with a terminal half-life of 1-6 minutes for exogenously administered oxytocin; clinical effects persist 20-30 minutes due to receptor binding. |
| Protein binding | Approximately 30%, bound primarily to serum albumin and oxytocin-specific binding proteins. |
| Volume of Distribution | 0.3 L/kg (total body water distribution; higher in pregnancy). Clinical meaning: reflects distribution to peripheral tissues and uterus. |
| Bioavailability | Intramuscular: approximately 50-80% due to first-pass metabolism; Intravenous: 100%; Oral: negligible (<1%) due to rapid peptidase degradation. |
| Onset of Action | Intravenous: 0.5-1 minute; Intramuscular: 2-5 minutes. |
| Duration of Action | Intravenous: 15-30 minutes (tonic uterine contraction); Intramuscular: 30-60 minutes. |
IV infusion: 0.5-2 mU/min, increase by 1-2 mU/min every 15-60 minutes until contractions are established; maximum 20 mU/min.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment required; monitor for fluid overload. |
| Liver impairment | No specific dose adjustment required. |
| Pediatric use | Not indicated for pediatric use. |
| Geriatric use | Use lowest effective dose; monitor for fluid overload and hypertension. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PITOCIN (PITOCIN).
| Breastfeeding | Oxytocin is rapidly metabolized in maternal plasma and gastrointestinal tract; negligible amounts enter breast milk. Estimated infant dose is <1% of maternal therapeutic dose. No adverse effects reported in breastfed infants. M/P ratio not established; oxytocin is not measurable in milk after IV administration. |
| Teratogenic Risk | Pitocin (oxytocin) is not associated with structural teratogenicity when used at therapeutic doses. However, prolonged high-dose exposure during labor may cause fetal distress, neonatal hyperbilirubinemia, and transient hyponatremia. In first trimester, no evidence of increased malformation risk. In second and third trimesters, use may induce uterine hyperstimulation leading to fetal hypoxia or uterine rupture. Risk is dose- and duration-dependent. |
■ FDA Black Box Warning
Only for use in hospital settings with adequate personnel and equipment. High doses or prolonged use may cause uterine hyperstimulation, tetanic contractions, or uterine rupture. Risk of water intoxication and hyponatremia due to antidiuretic effect.
| Serious Effects |
Hypersensitivity to oxytocin; significant cephalopelvic disproportion; unfavorable fetal presentation; fetal distress; hypertonic or hyperactive uterine patterns; contraindication to vaginal delivery; severe toxemia; invasive cervical cancer; previous uterine surgery (relative).
| Precautions | Monitor uterine activity and fetal heart rate continuously. Use cautiously in grand multiparity, cervical trauma, or overdistended uterus. Avoid simultaneous IV administration of fluids containing electrolytes in large volumes to minimize water intoxication. |
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| Fetal Monitoring | Continuous fetal heart rate monitoring (cardiotocography) and maternal uterine activity monitoring (tocodynamometry) are required during infusion. Assess maternal blood pressure (risk of hypotension with rapid IV bolus) and fluid balance (risk of water intoxication). Monitor for signs of uterine hyperstimulation or tetanic contractions. Postpartum, monitor for retained placenta and neonatal Apgar scores. |
| Fertility Effects | No known adverse effects on fertility. Oxytocin is not used for fertility treatment; high doses may disrupt implantation if used during luteal phase, but not relevant in clinical use for labor induction/augmentation. |