Intravenous Treatment and prophylaxis of postpartum haemorrhage
Adult: 5 units given via infusion over 5 minutes. Dosing instructions may vary between countries, refer to specific product guidelines.
Intravenous Labour induction
Adult: 1-4 milliunits/minute via infusion, may increase at intervals of at least 20 minutes in increments of 1-2 milliunits/minute until a max of 3-4 contractions occur every 10 minutes. Discontinue if regular contractions are not established after a total of 5 units, may be repeated on the following day starting again from a rate of 1-4 milliunits/minute. Max rate: 20 milliunits/minute. Dosing instructions may vary between countries, refer to specific product guidelines.
Intravenous Adjunct in abortion
Adult: In incomplete, inevitable or elective abortion: Initially, 5 units given via slow inj over 5 minutes, may be followed by an infusion at a rate of 20-40 milliunits/minute as necessary. Dosing instructions may vary between countries, refer to specific product guidelines.
Reconstitution
Vials labelled as 5 IU and 10 IU should be reconstituted with 500 and 1000 mL of 0.9% NaCl or lactated ringer’s solution respectively. Instructions for reconstitution vary depending on the indication and country of use, refer to detailed product guidelines.
Incompatibility
Incompatible with fibrinolysin, norepinephrine bitartrate, prochlorperazine edisylate, warfarin Na, solutions containing bisulphites and metabisulphites as preservatives.
Contraindications
Hypertonic uterine contractions, mechanical obstruction to delivery, foetal distress; conditions wherein spontaneous labour or vaginal delivery is contraindicated (e.g. significant cephalopelvic disproportion, foetal malpresentation, placenta praevia, vasa praevia, placental abruption, cord presentation or prolapse, overdistension or impaired resistance of the uterus to rupture, multiple pregnancy, polyhydramnios, grand multiparity); presence of a uterine scar from previous surgery including caesarean section. Prolonged use in resistant uterine inertia, severe CV disease, severe pre-eclamptic toxaemia.
Special Precautions
Women with borderline cephalopelvic disproportion, secondary uterine inertia, mild or moderate degrees of pregnancy-induced hypertension, CV disease (e.g. hypertrophic cardiomyopathy, valvular heart disease, ischaemic heart disease, coronary artery vasospasm), long QT syndrome, haemodynamically unstable states, history of lower-uterine-segment caesarean section. Women ≥35 years. Not intended for elective induction of labour. Pregnancy and lactation.
Adverse Reactions
Significant: Foetal distress, arrhythmias, hypotension, myocardial ischaemia, peripheral vasodilation, tachycardia, QT prolongation, uterine hypertonicity, spasm, tetanic contraction, disseminated intravascular coagulation (DIC). Cardiac disorders: Bradycardia. Gastrointestinal disorders: Nausea, vomiting. Immune system disorders: Anaphylaxis. Nervous system disorders: Headache. Pregnancy, puerperium and perinatal conditions: Postpartum haemorrhage. Reproductive system and breast disorders: Pelvic hematoma. Potentially Fatal: Water intoxication, hypertension, subarachnoid haemorrhage, rupture of the uterus.
Monitor fluid intake and output, uterine activity, maternal blood pressure, and foetal heart rate in relation to uterine contractions.
Overdosage
Symptoms: Water intoxication with convulsions; uterine hyperstimulation with hypertonic or tetanic contractions, tumultuous labour, uterine rapture, cervical and vaginal lacerations, postpartum haemorrhage, and uteroplacental hypoperfusion. Management: Symptomatic and supportive treatment. To treat water intoxication, restrict fluid intake, promote diuresis, and correct electrolyte imbalance. Convulsions may be controlled by giving diazepam.
Drug Interactions
Enhanced effect of prostaglandins. Reduced therapeutic efficacy and increased risk of hypotension with inhalation anaesthetics (e.g. halothane, sevoflurane, desflurane, cyclopropane). Enhanced effect of vasoconstrictors and sympathomimetics. Increased risk of arrhythmia with drugs that may prolong QT interval.
Action
Description: Oxytocin, a cyclic nonapeptide, activates G-protein-coupled receptors at the uterus, which causes an increase in intracellular Ca levels in uterine myofibrils, thus promoting uterine contractions. Onset: Uterine contractions: approx 1 minute. Duration: 1 hour. Pharmacokinetics: Distribution: Distributed throughout the extracellular fluid. Crosses placenta, enters breast milk (small amounts). Metabolism: Metabolised in the liver and kidneys. Excretion: Via urine (in small amounts and as unchanged drug). Elimination half-life: 1-6 minutes.
Chemical Structure
Oxytocin Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 439302, Oxytocin. https://pubchem.ncbi.nlm.nih.gov/compound/Oxytocin. Accessed Nov. 25, 2020.
H01BB02 - oxytocin ; Belongs to the class of oxytocin and analogues. Used in posterior pituitary lobe hormone preparations.
References
Anon. Oxytocin. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 29/09/2020.Anon. Oxytocin. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 29/09/2020.Buckingham R (ed). Oxytocin. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 29/09/2020.Joint Formulary Committee. Oxytocin. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 29/09/2020.Oxyla 10 IU/mL Injection (PT. Novell Pharmaceutical Laboratories). MIMS Malaysia. http://www.mims.com/malaysia. Accessed 30/09/2020.Oxytocin Injection Solution (Fresenius Kabi USA, LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 29/09/2020.Syntocinon 10 IU/mL Concentrate for Solution for Infusion; Solution for Injection (Novartis Corporation [Malaysia] Sdn. Bhd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my/. Accessed 29/09/2020.Syntocinon 5 IU/mL Concentrate for Solution for Infusion (Mylan Products Ltd.). MHRA. https://products.mhra.gov.uk/. Accessed 29/09/2020.
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