Nifedipine vs. ritodrine for arresting preterm labor - Tips from Other Journals

Date: Nov, 1990

Nifedipine vs. Ritodrine for Arresting Preterm Labor The beta-receptor agonist ritodrine is commonly used to arrest premature labor. However, its use is associated with significant side effects, including nausea, vomiting, palpitations and chest pain. Because of these side effects, the calcium channel blocker nifedipine is being investigated for the treatment of preterm labor. In a prospective study of 66 patients with the onset of labor between 20 and 36 weeks of gestation, Ferguson and colleagues compared the tocolytic effects of nifedipine and ritodrine.

Thirty-three patients received nifedipine sublingually in 10-mg capsules. If uterine contractions persited after 20 minutes, this dose was repeated at intervals of 20 minutes, up to maximum dose of 40 mg during the first hour of treatment. The remaining 33 patients received intravenous ritodrine, 50 [micrograms] per minute. If necessary, the infusion rate was increased by 50 [micrograms] per minute every 15 to 30 minutes, until a maximum dose of 350 [micrograms] per minute was reached or unacceptable side effects developed. Five of the patients who received nifedipine initially did not respond and were given ritodrine. Similary, five of the patients who received ritodrine initially were given nifedipine because of treatment failure.

Among the nifedipine-treated group, delivery was delayed 48 hours in 84 percent of patients, seven days in 70 percent and until the 36th week of gestation in 41 percent. With ritodrine, delivery was delayed 48 hours in 72 percent, seven days in 63 percent and until the 36th week of gestation in 52 percent.

Nifedipine was associated with significantly fewer side effects. Eighteen of 38 women treated with ritodrine (including five crossover patients) had side effects, compared with only five of 38 women treated with nifedipine (including five crossovers). Fetal and neonatal outcomes were similar in both groups.

On the basis of this study, it appears that nifedipine is comparable but not superior to ritodrine. The authors caution, however, that further study is needed before nifedipine is recommended for the treatment of preterm labor. (American Journal of Obstetrics and Gynecology, July 1990, vol. 163, p. 105.)

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