Objective This study was undertaken to evaluate whether the administration of meperidine decreases the length of labor in patients with a diagnosis of dystocia during the first stage of labor. Study design Women with term singleton pregnancies who received a diagnosis of dystocia and required an active management of labor were randomly assigned to receive either 100 mg of meperidine or placebo. The primary outcome measure was length of labor. Results Four hundred seven pregnant women were included. There were no significant statistical differences between meperidine and placebo groups in length of labor and operative delivery rates such as forceps and cesarean section by intentiontotreat analysis. Low Apgar scores, umbilical artery acidosis, and admission to neonatal care units were increased in the meperidine group. Conclusion Because of the absence of any benefits in patients with dystocia in labor and the presence of harmful effects on neonatal outcomes, meperidine should not be used during labor for this specific indication. Objective This study was undertaken to evaluate whether the administration of meperidine reduce the length of labor in patients with a diagnosis of dystocia during the first stage of labor. Study design Women with term singleton pregnancies who received a diagnosis of dystocia and required an active management of The first outcome measure was length of labor. There are no significant statistical differences between meperidine and placebo groups in length of labor and operative delivery rates such as forceps and cesarean section by intentiontotreat analysis. Low Apgar scores, umbilical artery acidosis, and admission to neonatal care units were increased in the meperidine group. Conclusion Because of the absence of any benefits in patients with dystocia in labor and the presence of harmful effects on neonatal outcomes, meperidine should not be used during labor for this specific indication