Single dose pharmacokinetics of syrup of ipecac.

Abstract

Syrup of ipecac (SI) has been used medicinally since the 1500s; however, little is known about the pharmacokinetics in humans of SI's active ingredients, emetine and cephaeline. The objective of this study was to evaluate the rate of absorption and the rate of elimination of emetine and cephaeline. Ten healthy, adult, human volunteers between 18 and 45 years of age who were of ideal body weight (body mass index 20-25) completed this study. After an overnight fast, 30 mL SI were ingested. Blood samples were collected 30, 45, 60, 90, 120, 150, and 180 minutes post-ingestion and urine was collected throughout the study period. Plasma and urine concentrations of emetine and cephaeline were measured by reverse-phase HPLC with fluorescence detection. In virtually all subjects, emetine and cephaeline were detected within 5-10 minutes of dosing with the time to maximum concentration being approximately 20 minutes. The mean areas under the concentration-time curve (AUC) for both emetine and cephaeline were similar; however, the ratio of mean cephaeline maximum concentration (Cmax) to emetine Cmax was approximately 1.5. Four of the ten subjects exhibited a type of concentration-time profile in which the levels of cephaeline were substantially higher than those of emetine and the levels of cephaeline were substantially higher than noted for the other six subjects. In these remaining six subjects, the levels of emetine and cephaeline were lower than 10 ng/mL at all time-points. An initial elimination phase was noted in some subjects but not in others. Individuals in whom an initial elimination phase was not observed also exhibited low levels of both alkaloids as compared with the other subjects suggestive of a slower distribution phase. Less than 0. 15% of the administered emetine and cephaeline was recovered in the urine at 3 hours. No relationship between vomiting episodes and peak concentrations of emetine or cephaeline was found. Administration of SI results in rapid appearance and disappearance of emetine and cephaeline in plasma becoming almost undetectable at 3 hours. Very little of either alkaloid is eliminated in the urine within this time period, suggesting extensive distribution. The length of time that an administered dose of SI can result in the detection of emetine and/or cephaeline in the urine has not been determined; future studies in humans are required.