Epidosin (Valethamate Bromide) Dosing for Labour
Epidosin (valethamate bromide) should be administered at 8 mg intramuscularly when cervical dilatation reaches 3–4 cm in active first‑stage labour, repeated every hour for a maximum of three doses (total 24 mg). 1, 2
Standard Dosing Protocol
- Initial dose: 8 mg intramuscularly at 3–4 cm cervical dilatation 1, 2
- Repeat dosing: 8 mg every hour 1, 2
- Maximum doses: Three injections (total 24 mg over 2–3 hours) 1, 2
- Timing: Begin administration only after establishing active labour with regular contractions and cervical dilatation of at least 3–4 cm 1, 2
Expected Clinical Effects
- Cervical dilatation rate: Increases to approximately 1.86–2.4 cm/hour (compared to 1.0–1.9 cm/hour without medication) 1, 2
- Duration of first stage: Reduces by approximately 60–90 minutes compared to no intervention 1, 3, 4
- Injection‑to‑delivery interval: Approximately 206–221 minutes (3.4–3.7 hours) 1, 2
- Normal vertex delivery rate: Not significantly affected by valethamate administration 3, 4
Common Side Effects to Monitor
Maternal effects that occur transiently with valethamate include: 1, 2
- Maternal tachycardia (most common)
- Fetal tachycardia
- Facial flushing
- Dry mouth
These side effects are more frequent with valethamate than with alternative antispasmodics like drotaverine, though no serious maternal or neonatal adverse events have been reported in clinical trials. 1, 2, 3
Important Clinical Caveats
Do not administer if:
- Cervical dilatation is less than 3 cm (not yet in active labour) 1, 2
- Evidence of fetal distress is present 3
- Uterine rupture or dehiscence is suspected 3
- Known hypersensitivity to anticholinergic agents exists 3
Monitoring requirements:
- Assess maternal heart rate before each dose and 15–30 minutes after administration 1, 2
- Monitor fetal heart rate continuously during labour 3
- Document cervical dilatation progress hourly 1, 2
Comparative Efficacy Context
While valethamate bromide is effective for labour augmentation, evidence from head‑to‑head trials demonstrates that drotaverine hydrochloride produces faster cervical dilatation (3.0 cm/hour versus 2.4 cm/hour) and shorter injection‑to‑delivery intervals (183 minutes versus 207 minutes) with fewer side effects. 1, 2 However, valethamate remains a reasonable option when drotaverine is unavailable, as it still significantly reduces first‑stage labour duration compared to no intervention (reduction of 65–74 minutes). 3, 4
The overall quality of evidence supporting antispasmodics in labour is low to moderate, with significant heterogeneity across studies and inconsistent reporting of maternal and neonatal safety outcomes. 3, 4 Nevertheless, the consistent finding across multiple trials is that valethamate accelerates cervical dilatation without increasing operative delivery rates. 3, 4