RT Journal Article SR Electronic T1 Elimination of chronically consumed caffeine in the pregnant monkey (Macaca fascicularis). JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 891 OP 897 VO 239 IS 3 A1 Gilbert, S G A1 So, Y A1 Klassen, R D A1 Geoffroy, S A1 Stavric, B A1 Rice, D C YR 1986 UL http://jpet.aspetjournals.org/content/239/3/891.abstract AB Characterization of alterations in caffeine elimination during pregnancy is essential in assessing the potential exposure of the fetus to caffeine and its metabolites. Female monkeys (Macaca fascicularis) were exposed to caffeine in their drinking water 7 days/week before, during and after pregnancy. The low exposure (0.15 mg/ml) corresponded to a level sometimes consumed by pregnant women (10-15 mg/kg/day) whereas the high exposure (0.35 mg/ml) was above average human consumption (25-30 mg/kg/day). Blood samples and 24-hr urine samples were collected every 2 weeks throughout dosing. Caffeine and metabolite concentrations in serum and urine were determined by high-performance liquid chromatography. Before pregnancy, geometric mean serum caffeine concentrations were approximately 1.6 and 4.9 micrograms/ml and serum theophylline concentrations were 6.6 and 13.3 micrograms/ml for the low and high dose groups, respectively. During pregnancy, serum caffeine concentrations increased by approximately 100% for both dose groups and, after parturition, declined to prepregnancy concentrations. Serum theophylline concentrations were usually greater than serum caffeine concentrations and did not change during pregnancy. The amount of caffeine and theophylline excreted in the urine over 24 hr increased during pregnancy and returned to prepregnancy levels after parturition. The results of this study indicate that pregnancy decreased caffeine elimination, resulting in a significant increase in serum caffeine levels. The changes in caffeine elimination may be related to alterations in serum estrogen and progesterone levels.