What are the maternal and fetal side effects of hyoscine butylbromide and scopolamine when used in pregnant women during active labor?

Side Effects of Hyoscine Butylbromide and Scopolamine in Pregnant Women During Active Labor

Hyoscine Butylbromide (HBB) - Maternal Side Effects

Hyoscine butylbromide demonstrates an excellent safety profile during labor with minimal to no serious adverse maternal effects reported across multiple randomized controlled trials. 1, 2, 3, 4, 5

Common Maternal Effects

• No serious adverse maternal events were documented in randomized trials involving over 1,400 pregnant women receiving HBB during active labor 1, 2, 3, 4, 5
• Maternal tachycardia is theoretically possible but was not reported as clinically significant in labor studies 1
• Dry mouth and other anticholinergic effects are minimal when used as a single intravenous dose during labor 4, 5

Obstetric Outcomes

• No increase in cesarean section rates compared to placebo (statistically insignificant slight increase noted in one trial) 3, 5
• No increase in postpartum hemorrhage rates 5
• No increase in instrumental delivery rates 5

Hyoscine Butylbromide - Fetal/Neonatal Side Effects

Hyoscine butylbromide shows no adverse fetal or neonatal effects when administered during labor, with reassuring Apgar scores across all studies. 1, 2, 3, 4, 5

Neonatal Outcomes

• Apgar scores at 1 and 5 minutes were comparable between HBB and control groups 2, 3, 4, 5
• No short-term adverse neonatal effects were observed in any randomized trial 4
• Neonatal condition at birth was not compromised by maternal HBB administration 4

Scopolamine (Transdermal/Parenteral) - Maternal Side Effects

Scopolamine carries significantly more maternal risks than hyoscine butylbromide, particularly central nervous system and anticholinergic effects, and should be avoided in pregnant women with severe preeclampsia. 6

Common Maternal Effects (from FDA labeling)

• Dry mouth (29% vs 16% placebo) - most common adverse effect 6
• Dizziness (12% vs 7% placebo) 6
• Somnolence/drowsiness (8% vs 4% placebo) 6
• Agitation (6% vs 4% placebo) 6
• Visual impairment including mydriasis (5% and 4% respectively) 6
• Confusion (4% vs 3% placebo) 6

Serious Maternal Risks

• Eclamptic seizures have been reported in pregnant women with severe preeclampsia soon after intravenous or intramuscular scopolamine administration 6
• Acute psychosis including hallucinations, disorientation, and paranoia (postmarketing reports) 6
• Angle closure glaucoma (postmarketing reports) 6
• Amnesia, coordination abnormalities, speech disorders, and restlessness 6

Critical Contraindication

• Avoid scopolamine in patients with severe preeclampsia due to documented cases of eclamptic seizures following administration 6

Scopolamine - Fetal/Neonatal Effects

Limited data exist on fetal effects of scopolamine during labor, though animal studies showed embryotoxicity at high doses. 6

Available Safety Data

• Embryotoxicity observed in rabbits at intravenous doses producing plasma levels approximately 100 times higher than human therapeutic levels 6
• No adverse effects on uterine contractions or labor duration in animal studies 6
• Scopolamine is present in human milk, though effects on breastfed infants are unknown 6
• Pediatric patients are particularly susceptible to adverse reactions including mydriasis, hallucinations, amblyopia, and drug withdrawal syndrome 6

Key Clinical Distinctions

Hyoscine butylbromide is the preferred agent for labor augmentation due to its superior safety profile, while scopolamine should generally be avoided during pregnancy and labor. 1, 2, 3, 4, 5, 6

Why HBB is Safer

• Quaternary ammonium structure limits systemic absorption and CNS penetration 7
• Minimal placental transfer due to ionization at physiological pH 7
• Single-dose intravenous administration (20-40 mg) during active labor minimizes exposure 2, 4, 5
• No documented serious maternal or fetal adverse events in over 1,400 patients across multiple RCTs 1, 5

Why Scopolamine Carries More Risk

• Tertiary amine structure allows CNS penetration and systemic effects 7, 6
• Documented eclamptic seizures in severe preeclampsia 6
• High incidence of CNS effects (dizziness, confusion, hallucinations) 6
• Crosses placenta and is present in breast milk 6

Important Clinical Caveats

• Elderly patients and those with CNS disorders are at increased risk for neurologic and psychiatric adverse reactions with scopolamine 6
• Drug interactions are significant with scopolamine when combined with other CNS depressants, anticholinergics, or sedatives 6
• HBB should be given as a single intravenous dose (not repeated dosing) to minimize any theoretical anticholinergic effects 5
• Monitor for maternal tachycardia if using any anticholinergic agent, though this was not clinically significant in HBB labor studies 1