Maternal and fetal response to alphaprodine during labor. A preliminary study.

Alphaprodine is a synthetic narcotic, structurally similar to meperidine. Respiratory depression has been reported as a not-infrequent side effect when larger doses of alphaprodine were used, particularly intravenously. In this study, the maternal respiratory rate and tissue pO2 and pCO2 were determined in patients receiving alphaprodine, 0.4 mg/kg of prepregnancy weight, for first-stage analgesia. Statistically significant falls in maternal tcpO2 and increases in tcpCO2 were observed. The baseline fetal heart rate decreased significantly 20 minutes after the injection (139 to 132 bpm). There was no increase in abnormal fetal heart rate patterns. The variability of the baseline fetal heart rate was unchanged until 25 minutes following alphaprodine administration, when a significant reduction occurred. The changes seen in the parameters monitored in this study were not associated with any clinically adverse effects on the mother or fetus.