Effectiveness and Safety of Isoxsuprine Hydrochloride as Tocolytic Agent in Arresting Active/Threatened Preterm Labor and Its Role in Maintenance Tocolysis: A Prospective, Open-Label Study

Abstract

Objective The aim of the study is to obtain insights on the short and long-term safety and effectiveness of isoxsuprine hydrochloride as a tocolytic agent in the management of PTL. Study Design In this prospective, single-center, noncomparative study, patients (with preterm labor at gestational age of 24–37 weeks) were administered intravenous (IV) infusion of 40-mg isoxsuprine hydrochloride until uterine quiescence, followed by intramuscular (IM) injection of isoxsuprine hydrochloride 10 mg/4-hourly for first 24 hours and maintained with retard 40-mg sustained release capsule (two times a day) till the time of delivery or 37 completed weeks of pregnancy. Results All patients (n = 50) achieved successful tocolysis in 24 hours and 48 hours postadministration of isoxsuprine hydrochloride (IV/IM/oral). Mean (±SD) gestation age at the time of delivery was 39.8 ± 2.1 weeks, with latency period of 58.5 ± 18.7 days. Pregnancy outcomes were normal in all the patients and no congenital anomaly/fetal infection was reported. Mean (±SD) fetal birth weight was 2.7 ± 0.3 kg; mean (±SD) Apgar score at 1 and 5 minutes were 7.5 ± 0.6 and 9.2 ± 0.4, respectively. Maternal tachycardia and vomiting (8.0% each) were the commonly reported adverse drug reactions, which were resolved with dose adjustment. Conclusion Isoxsuprine was found to be an effective and well-tolerated tocolytic agent in arresting PTL, in turn resulting in the overall improvement in maternal and perinatal outcomes.

Oral nifedipine and parenteral isoxsuprine in arresting preterm labor

“…In a study conducted by Jaju,[ 11 ] the most common side effects of isoxsuprine were maternal tachycardia, vomiting, and facial flushing, while tachycardia was the major side effect of nifedipine. Furthermore, peripheral vasodilation by isoxsuprine causes decreased peripheral vascular resistance.…”

“…[ 18 ] This comparatively high incidence of RDS, tachycardia, and low APGAR score in the isoxsuprine group could be due to the direct transplacental passage of the drug and a direct effect on the fetal myocardium, resulting in adverse neonatal outcomes after birth. [ 11 ]…”

“…[ 4 ] Previous studies have demonstrated that isoxsuprine, when administered intravenously along with maintenance therapy (oral administration), is effective in pregnancy prolongation in women at risk of preterm delivery. [ 10 11 ] Studies have shown that nifedipine suppresses preterm labor with minimum fetal and maternal side effects. [ 12 ] Its administration has been associated with decreased blood flow in the uterus, causing fetal hypoxia and acidosis, maternal palpitation, and headache, and the safety data is not well established.…”

“…The available literature does not contain adequate number of studies comparing the effects of nifedipine and isoxsuprine as tocolytic agents. [ 11 ] The better tocolytic agent among the two still needs to be explored. Therefore, the present study focused on comparing the efficacy of oral nifedipine and parenteral isoxsuprine in arresting preterm labor.…”

Management Dilemmas in Threatened Preterm Labor (TPTL) and its Impact: A Mini Review

“…(29.73 ± 3.10 days vs. 11.13 ± 5.08 days). A study conducted in southern part of India to assess the efficacy of Isoxsuprine hydrochloride in threatened preterm labor showed 100% success rate and an apparent lengthening of pregnancy [15]. The main limitation of this study was its sample size (n=50) and it was a non-comparative study.…”