Effects of orally administered Clenbuterol on oxytocin-induced uterine activity

Abstract

Clenbuterol is a sympathicomimetic agent with a predominant effect on beta2-adrenergic receptors [6]. In addition to its bronchospasmolytic effect it inhibits uterine contractions and has been recommended for treatment of premature labor [6]. The results of pharmacokinetic studies in nonpregnant animals [4, 7] and in nonpregnant human individuals [8] indicate rapid absorption of an oral dose of Clenbuterol by the gastro-intestinal tract, resulting in relatively high plasma levels of the unchanged compound. Elimination of orally administered isotope-labelled Clenbuterol was shown to follow a biphasic curve with a half-life of 30— 35 hours in the second, slow phase [8]. If these pharmacologic properties would also be valid in pregnant women with uterine contractions, oral administration of Clenbuterol would appear to be an attractive approach to the treatment of premature labor. Therefore, the present study was designed to measure the effects of single oral doses of Clenbuterol on uterine activity as well as on variables of maternal and fetal cardiovascular function. The study was performed in term pregnant women with oxytocin-induced labor in order to obtain standardized uterine activity and to allow continuous measurement of in trauterine pressure and fetal heart rate.