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.