Comparison of the urinary metabolite profile of caffeine in young and elderly males.

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Abstract
The urinary metabolite profile of caffeine was compared in a group of seven healthy young men aged 18‐29 years and in a group of five healthy elderly men aged 66‐71 years. All subjects were given 5 mg/kg doses of caffeine as an aqueous oral solution or an intravenous infusion on two separate occasions in a randomized crossover design. Urine samples were collected for 24 h after dosing and analysed for caffeine and eleven of its metabolites by high‐performance liquid chromatography. The effects of age, route of administration, and order of administration by route on the metabolite profile of caffeine were examined. The route of administration and the order of administration by the two routes were found not to influence the urinary metabolite pattern significantly. The urinary metabolite profile did not vary substantially with age except for the observation that significantly greater amounts of 1‐ methyluric acid, 7‐methyluric acid and 1,7‐dimethyluric acid were excreted by the elderly subjects.