A double-blind placebo-controlled randomized trial on the effect of hyosine n-butyl bromide for improving duration of labor in term pregnancies.

Aim: To compare the effectiveness of intramuscular hyocine n-butyl bromide (HBB) with placebo for shortening the duration of the first stage of labor in term pregnancies.
Methods: A double blind placebo-controlled randomized trial of parturients who presented at term in the active phase of labor was conducted. They were randomly (1:1 ratio) given intramuscular injection of either 40 mg (2 mL) of HBB or 2 mL of water for injection as a placebo. The primary outcome measures were the duration of first and second stages of labor. Subgroup analysis of primigravid and multigravid women were also performed for various outcomes. We did intention-to-treat analysis.
Results: Sixty-two women were randomized to each group and none were lost to follow-up. Baseline characteristics were similar between the HBB and placebo groups. The mean duration of first stage of labor was noted to be significantly shorter in the HBB group for both the primigravidas (246.6 ± 21.9 vs 391.8 ± 56.6 min for control; P < 0.001) and for multigravidas (205.9 ± 17.8 vs 323.8 ± 16.0 min for control;P < 0.001).There was also significantly shorter duration of second stage of labor in the HBB group (primigravida: P = 0.013; multigravida: P = 0.016). The duration of third stage of labor, mode of delivery and maternal and/or neonatal outcomes for both classes of parturients were not significantly different.
Conclusion: HBB is effective in reducing the first and second stages of labor without adverse maternal or neonatal outcome. HBB does not significantly influence the duration of third stage of labor including mode of delivery. More evidence is needed to further explore the potential useful role of HBB in the active phase of labor.
(© 2020 Japan Society of Obstetrics and Gynecology.)