Drugs used in Obstetrics

Prostaglandins and oxytocics

Prostaglandins and oxytocics are used to induce abortion or induce or augment labour and to minimise blood loss from the placental site. They include oxytocin, carbetocin, ergometrine, and the prostaglandins. All induce uterine contractions with varying degrees of pain according to the strength of contractions induced.

CARBOPROST:

Indications: postpartum haemorrhage due to uterine atony in patients unresponsive to ergometrine and oxytocin.

Contraindications: untreated pelvic infection; cardiac, renal, pulmonary, or hepatic disease

Dose and Administration: By deep intramuscular injection, 250 micrograms repeated if necessary at intervals of 11/2 hours (in severe cases the interval may be reduced but should not be less than 15 minutes); total dose should not exceed 2 mg (8 doses).

DINOPROSTONE:

Indications: Cervical Ripening Procedure, Induction of Labor.

Contraindications: active cardiac, pulmonary, renal or hepatic disease; placenta praevia or unexplained vaginal bleeding during pregnancy, ruptured membranes, major cephalopelvic disproportion or fetal malpresentation, history of caesarean section or major uterine surgery, untreated pelvic infection, fetal distress, grand multiparas and multiple pregnancy, history of difficult or traumatic delivery; avoid extra-amniotic route in cervicitis or vaginitis.

Dose and Administration: By vagina, cervical ripening and induction of labour at term, 1 pessary (in retrieval device) inserted high into posterior fornix and removed when cervical ripening adequate; if oxytocin necessary, remove 30 minutes before oxytocin infusion; remove if cervical ripening inadequate after 24 hours (dose not to be repeated).

By vagina, induction of labour, inserted high into posterior fornix, 3 mg, followed after 6–8 hours by 3 mg if labour is not established; max. 6 mg.

METHYLERGOMETRINE:

Indications: For routine management after delivery of the placenta; postpartum atony and hemorrhage; subinvolution. Under full obstetric supervision, it may be given in the second stage of labor following delivery of the anterior shoulder.

Contraindications: Hypertension; toxemia; pregnancy; and hypersensitivity.

Dose and Administration: Intramuscularly, 1 mL, 0.2 mg, after delivery of the anterior shoulder, after delivery of the placenta, or during the puerperium. May be repeated as required, at intervals of 2-4 hours. Orally, One tablet, 0.125 mg, 3 or 4 times daily in the puerperium for a maximum of 1 week.

OXYTOCIN:

Indications: Induction of labour for medical reasons or stimulation of labour in hypotonic uterine inertia.

Contraindications: hypertonic uterine contractions, fetal distress; any condition where spontaneous labour or vaginal delivery inadvisable; avoid prolonged administration in oxytocin-resistant uterine inertia, severe pre-eclamptic toxaemia, or severe cardiovascular disease.

Dose and Administration: max. 5 units in 1 day (may be repeated next day starting again at 0.001–0.002 units/minute).

Ductus arteriosus

ALPROSTADIL:

Indications: Aorta Dextratransposition with Intact Ventricular Septum, Coarctation of Aorta, Congenital Atresia of Pulmonary Valve, Congenital Heart Defect Requiring Open Patent Ductus Arteriosus, Ebstein’s Anomaly of the Tricuspid Valve, Pulmonary Artery Stenosis, Tetralogy Of Fallot, Tricuspid Valve Atresia.

Contraindications: Apnea, Pyloroduodenal Obstruction, and Respiratory Distress Syndrome in the Newborn.

Dose and Administration: By intravenous infusion, initially 10 nanograms/kg/minute, adjusted according to response in steps of 5– 10 nanograms/kg/minute; max. 100 nanograms/kg/minute.

INDOMETHACIN:

Indications: Patent Ductus Arteriosus, Nephrogenic Diabetes Insipidus, Twin Reversal Arterial Perfusion Syndrome.

Contraindications: Pregnancy, Blood Coagulation Disorder, Depression, Gastrointestinal Ulcer, Parkinsonism, Renal Disease, and Tobacco Smoker.

Dose and Administration: By intravenous injection, over 20–30 minutes, 3 doses at intervals of 12–24 hours, neonate under 48 hours, 200 micrograms/kg then 100 micrograms/kg then 100 micrograms/kg; neonate 2–7 days, 200 micrograms/kg then 200 micrograms/kg then 200 micrograms/kg; neonate over 7days, 200 micrograms/kg then 250 micrograms/kg then 250 micrograms/kg; solution prepared with 1–2 mL sodium chloride 0.9% or water for injections (not glucose and no preservatives).

Myometrial relaxants

Tocolytic drugs postpone premature labour and they are used with the aim of reducing harm to the child. However, there is no satisfactory evidence that the use of these drugs reduces mortality. The greatest benefit is gained by using the delay to administer corticosteroid therapy or to implement other measures which improve perinatal health (including transfer to a unit with neonatal intensive care facility).

ATOSIBAN:

Indications: uncomplicated premature labour.

Contraindications: eclampsia and severe pre-eclampsia, intra-uterine infection, intra-uterine fetal death, antepartum haemorrhage (requiring immediate delivery), placenta praevia, abruptio placenta, intra-uterine growth restriction with abnormal fetal heart rate, premature rupture of membranes after 30 weeks’ gestation.

Dose and Administration: By intravenous injection, initially 6.75 mg over 1 minute, then by intravenous infusion 18 mg/hour for 3 hours, then 6 mg/hour for up to 45 hours; max. duration of treatment 48 hours.

RITODRINE HYDROCHLORIDE:

Indications: uncomplicated premature labour.

Contraindications: in cardiac disease and in patients with significant risk factors for myocardial ischaemia; also be avoided in antepartum haemorrhage, intra-uterine infection, intra-uterine fetal death, placenta praevia, abruptio placenta, threatened miscarriage, cord compression, and eclampsia or severe pre-eclampsia.

Dose and Administration: By intravenous infusion, initially 50 micrograms/minute, increased gradually according to response by 50 micrograms/minute every 10 minutes until contractions stop or maternal heart rate reaches 140 beats per minute; continue for 12–48 hours after contractions cease(usual rate 150–350 micrograms/minute); max. rate
350 micrograms/minute; or by intramuscular injection, 10 mg every 3–8 hours continued for 12–48 hours after contractions have ceased; then by mouth (but see notes above), 10 mg 30 minutes before termination of intravenous infusion, repeated every 2 hours for 24 hours, followed by 10–20 mg every 4–6 hours, max. oral dose 120 mg daily. Orally, 10 to 20 mg every four to six hours.