Abstract
Evaluation of: Smith GN, Walker MC, Ohlsson A, O’Brien K, Windrim R; Canadian Preterm Labour Nitroglycerin Trial Group. Randomized double-blind placebo-controlled trial of transdermal nitroglycerin for preterm labor. Am. J. Obstet. Gynecol. 196(1), 37.e1–37.e8 (2007).
The aim of finding a new tocolytic drug through the adaptation of a substance commonly utilized for other pathologies but that has been proven to have a tocolytic effect in vitro or in vivo deserves to be explored. However, care must be taken to avoid misleading results, especially when protocols are not carefully designed. On the basis that glyceril trinitrate (GTN) has been found in both animal and human studies to act as a tocolytic agent with unclear maternal–fetal side effects, a multicenter, randomized, placebo-controlled trial was set up by the Canadian Preterm Labour Nitroglycerin Trial Group and the results were recently published. The risk of developing neonatal morbidity was reduced by 79% if mothers were treated with GTN. Moreover, nitric oxide donor treatment led to a reduction in the risk of a birth before 28 weeks’ gestation compared with placebo. This article analyzes the study, provides and discusses the rationale, results and pitfalls, and concludes that the Canadian study cannot add any support for the routine application and prescription of these drugs. There is much to be done before the true efficacy and safety of GTN can be determined, with the ultimate aim being an accurate reflection of its performance in clinical practice.