Full Prescribing Info
Each mL contains: Oxytocin BP 10 I.U.
Water for Injection BP q.s.
Pharmacology: Pharmacodynamics: Uterine motility depends on the formation of the contractile protein actomyosin under the influence of the Ca2-dependent phosphorylating enzyme myosin light-chain kinase. Oxytocin promotes contraction by increasing the intracellular Ca2. Oxytocin has specific receptors in the myometrium and the receptor concentration increase greatly during pregnancy, reaching a maximum in early labor at term. The response to a given dose of oxytocin is very individualized and depends on the sensitivity of the uterus, which determined by the Oxytocin receptor concentration. Oxytocin and vasopressin differ in regards to only two of the eight amino acids.
Pharmacokinetics: Intravenous infusion: When Oxytocin injection is given by continuous I.V. Infusion at doses appropriate for induction or enhancement of labour the uterine response sets in gradually and usually reaches a steady state within 20 to 40 minutes. The corresponding plasma levels of oxytocin are comparable to those measured during spontaneous first-stage labour. For example, oxytocin plasma levels in 10 pregnant women at term receiving a 4 milliunits per minute intravenous infusion were 2 to 5 microunits/mL. Upon discontinuation of the infusion, or following a substantial reduction in the infusion rate, e.g. in the event of over stimulation, uterine activity declines rapidly but may continue at an adequate lower level.
Intravenous injection and intramuscular injection: When administered by I.V. or I.M. Injection for prevention or treatment of post-partum hemorrhage, Oxytocin Injection acts rapidly with a latency period of less than 1 minute by I.V. Injection and of 2 to 4 minutes by I.M. Injection. The oxytocin response last for 30 to 60 minutes after I.M. administration, possibly less after I.V. Injection.
Distribution: Oxytocin distributes throughout the extracellular fluid, with minimal amounts reaching the foetus. The steady-state distribution volume determined in 6 healthy men after intravenous injection was 12.2 L or 0.17 L/kg. Plasma protein binding is very low. Oxytocin may be found in small quantities in mother's breast milk.
Elimination: The relative ease with which the rate and force uterine contractions can be regulated by the I.V. infusion of Oxytocin Injection is due to the short half-life of oxytocin. Values reported by various investigators range from 3 to 20 minutes. Removal of oxytocin from plasma is accomplished mainly by the liver and by the kidneys. The metabolic clearance rate amounts to about 20 mL/kg per minute in men as well as in pregnant women. Less than 1% of a given dose is excreted unchanged in the urine.
For induction or stimulation of labour in hypotonic uterine inertia, prevention and treatment of post-partum uterine atony and hemorrhage, and early pregnancy as adjunct therapy for management of incomplete, inevitable or missed abortion.
Dosage/Direction for Use
Induction or enhancement of labor: I.V. drip infusion 10 IU added to 1L physiologic saline electrolyte solution. For patients whom infusion of NaCl must be avoided use 5% dextrose solution as diluent. Initial infusion rate 1-4 mU/min (2-8 drops/min). Gradually increase intervals <20 min. until a contraction pattern similar to that of normal labor is established. Max. rate: 20 mU/min (40 drops/ min).
Caesarean section: 5 IU by slow I.V. injection immediately after delivery.
Prevention of post-partum uterine hemorrhage: 5 IU infusion followed in severe cases by I.V. infusion of 5-20 IU of oxytocin in 500 ml of non-hydrating diluent.
Missed abortion: 5 IU, I.M. or slowly I.V., if necessary, followed by I.V. Infusion 20-40 mU/min.
Or as prescribed by the physician.
Hypertonic uterine contraction, mechanical obstruction to delivery, fetal distress, significant cephalopelvic disproportion, fetal malabsorption, placenta previa, placenta abruption, cord presentation or prolapse, over distention or impaired resistance of the uterus to rupture as in multiple pregnancy, polyhydramnios, grand multiparity and in uterine scars. Do not use for prolonged period in patients with oxytocin-resistant uterine inertia, severe pre-eclamptic toxemia or severe CV disorder.
Special Precautions
Administration should be under hospital condition and qualified medical supervision. For induction and enhancement of labour administer only as an I.V. infusion. Carefully monitor fetal heart rate and motility. Caution use in borderline Cephalopelvic disproportion, secondary uterine inertia mild to moderate degrees of pregnancy-induced HPN or cardiac disease and patients >35 year or with history of lower-uterine-segment caesarian section. Avoid tumultuous labor in fetal death and utero and/or meconium-stained amniotic hemorrhage. Avoid rapid I.V. infusion.
Adverse Reactions
Uterine spasm, in low doses. High doses may result in uterine over stimulation that may cause fetal distress, asphyxia, and death, or may lead to hypertonicity, tetanic contractions, soft tissue damage or rupture of the uterus. Rapid I.V. bolus injection may cause short-lasting hypotension accompanied with flushing and relax tachycardia.
Drug Interactions
Prostaglandin, inhalation, anesthetics e.g., cyclopropane or halothane, sympathomimetic vasoconstrictor agent.
Store at temperatures between 2°C-8°C. Do not freeze.
MIMS Class
Drugs Acting on the Uterus
ATC Classification
H01BB02 - oxytocin ; Belongs to the class of oxytocin and analogues. Used in posterior pituitary lobe hormone preparations.
Soln for inj (amp) 10 IU/mL x 1 mL x 5's.
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