SYNTOCINON
Clinical safety rating
cautionComprehensive clinical and safety monograph for SYNTOCINON (SYNTOCINON).
Comprehensive clinical and safety monograph for SYNTOCINON (SYNTOCINON).
Induction or augmentation of laborFacilitation of abortion in the second trimesterPostpartum hemorrhage prevention and treatment
Vomiting, Headache, Uterine contractions, Nausea
Synthetic oxytocin binds to oxytocin receptors in the myometrium, causing increased intracellular calcium and uterine smooth muscle contraction. Also acts on mammary gland myoepithelium for milk ejection.
| Metabolism | Rapidly metabolized in the liver and kidneys by oxytocinase (cysteine aminopeptidase) and other peptidases. |
| Excretion | Renal: >99% as intact oxytocin; biliary/fecal: negligible (<1%). |
| Half-life | Terminal elimination half-life: 1–6 minutes (intravenous); 1–9 minutes (intramuscular). Clinically, effects dissipate rapidly after infusion cessation. |
| Protein binding | Low (~30%); primarily binds to albumin and oxytocin-specific carrier proteins (e.g., neurophysin I). |
| Volume of Distribution | 0.2–0.3 L/kg; reflects limited distribution into extracellular fluid and minimal tissue binding. |
| Bioavailability | Intramuscular: ~20–40% (due to rapid enzymatic degradation); Intravenous: 100%. |
| Onset of Action | Intravenous: 1–2 minutes; Intramuscular: 3–5 minutes. |
| Duration of Action | Intravenous: 15–60 minutes (dose-dependent); Intramuscular: 30–120 minutes. Uterine response wanes quickly after infusion stop. |
| Molecular Weight | 1007.2 |
| Action Class | Uterotonic and abortificient |
| Brand Substitutes | Itocin 5IU Injection, Wotocin 5IU Injection, Indox 5IU Injection, Zygon 5IU Injection, Labtocin 5IU Injection |
10 units (1 mL) intravenously as a single dose after delivery; continuous infusion: 20 units in 1 L of normal saline or lactated Ringer's solution at 2-10 mU/min (0.1-0.5 mL/min) titrated to uterine response.
| Dosage form | INJECTABLE |
| Renal impairment | No dosage adjustment required for renal impairment; oxytocin is rapidly metabolized and renally excreted, but no specific GFR-based guidelines exist. |
| Liver impairment | No dosage adjustment required for hepatic impairment; oxytocin is metabolized primarily by the liver, but no Child-Pugh based modifications have been established. |
| Pediatric use | Not indicated for pediatric use; safety and efficacy in children have not been established. |
| Geriatric use | Use with caution in elderly patients due to potential for uterine hyperstimulation and adverse cardiovascular effects; no specific dosage adjustments recommended. |
| 1st trimester | Limited data; risk cannot be ruled out. Use only if clearly indicated. |
| 2nd trimester | Use only for clear medical indications; may cause uterine hypertonus or rupture. |
| 3rd trimester | Contraindicated for obstetric use except during labor; high risk of uterine rupture. |
Clinical note
Comprehensive clinical and safety monograph for SYNTOCINON (SYNTOCINON).
| Placental transfer | Crosses placenta; endogenous oxytocin similarly crosses. Exogenous oxytocin may induce uterine contractions. |
| Breastfeeding | Excreted in breast milk in negligible amounts; not expected to cause adverse effects in infants. However, use with caution in mothers with cardiovascular disease or preeclampsia. |
| Lactation Rating | L1 (Safe) |
| Teratogenic Risk | Syntocinon (oxytocin) is not associated with teratogenic effects when used at standard doses for labor induction. However, prolonged high-dose exposure may cause fetal hypoxia, bradycardia, and neonatal hyperbilirubinemia. No trimester-specific malformation risk is established; uterine hyperstimulation risk is greatest during second and third trimester use. |
| Fetal Monitoring | Continuous fetal heart rate monitoring and uterine activity assessment via tocodynamometry or intrauterine pressure catheter. Monitor maternal vital signs, fluid balance (risk of water intoxication with prolonged infusion), and signs of uterine hyperstimulation. |
| Fertility Effects | No known adverse effects on fertility. Used therapeutically to induce labor; does not impair future fertility. |
■ FDA Black Box Warning
NOT FOR ELECTIVE INDUCTION OF LABOR AT TERM DUE TO RISK OF UTERINE HYPERSTIMULATION, UTERINE RUPTURE, AND FETAL DISTRESS. SHOULD ONLY BE USED UNDER CONTINUOUS MEDICAL SUPERVISION WITH FETAL AND UTERINE MONITORING.
| Serious Effects |
Hypersensitivity to oxytocin or any componentSignificant cephalopelvic disproportionUnfavorable fetal positions (e.g., transverse lie)Obstetric emergencies where surgical intervention is favoredFetal distress when not imminent deliveryActive genital herpes infectionElective induction of labor when such is contraindicatedUterine hypertonus or co-existing pathologic uterine activityPlacenta previa or vasa previaCord prolapse
| Precautions | Uterine hyperstimulation and tetany, Uterine rupture, especially in grand multipara or with prior cesarean, Water intoxication and hyponatremia due to antidiuretic effect (high doses), Fetal bradycardia, hypoxia, and neonatal jaundice, Hypotension and tachycardia with rapid IV administration |
| Food/Dietary | No food interactions are known. However, because oxytocin can cause water retention, advise moderate sodium intake to reduce risk of hyponatremia. No specific dietary restrictions. |
| Clinical Pearls | Syntocinon (oxytocin) is used for induction or augmentation of labor. Administer via controlled IV infusion using an infusion pump. Start at 0.5-2 mU/min and titrate every 30-60 min to achieve adequate contractions (3-5 per 10 min). Monitor for uterine hyperstimulation, fetal distress, or water intoxication (antidiuretic effect). Have magnesium sulfate, terbutaline, or other tocolytics available for hyperstimulation. Do not use if contraindicated (e.g., cephalopelvic disproportion, fetal distress, placenta previa). |
| Patient Advice | Syntocinon is given intravenously to start or strengthen labor contractions. · You will be closely monitored with an electronic fetal monitor. · Report any excessively frequent or prolonged contractions or severe pain immediately. · It may increase the risk of postpartum hemorrhage; staff is prepared to manage it. · Tell your healthcare provider about any history of heart disease or high blood pressure. |
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