Profile of urinary caffeine excretion in Indonesian volunteers

Thirty one volunteers (15-30 years old, 42-78 kg, 26 men, 5 women) were recruited and completed the study. The volunteers fulfilled the inclusion criteria (healthy, no previous history of chronic diseases or sensitivity to caffeine), passed medical examination (physical examinations, blood chemistry determination, chest-X-ray and treadmill exercise test) and signed a letter of informed consent. All volunteers had undergone a week wash-out period of free caffeine before entering the study, stayed in lodging and were provided with standard food and drink. A medical doctor, a nurse and an ambulance were available on site during the study period. Each volunteer drank 3 bottles of a brand beverage which provided 240 mg caffeine per person, at one time. Thereafter the urinary caffeine excretion was determined at various time points up to 50 hours. Urinary caffeine concentration was determined by means of high performance liquid chromatography (HPLC). The range of maximum urinary caffeine excretion of most volunteers was 5.00-5.99 μg.ml^-1. Peak excretion occurred at 3 hours after caffeine drinking. The mean or cumulative caffeine excreted in the urine from all volunteers at hour 2 was 1.13±0.76 mg.h^-1. After 32 hour, caffeine could no longer be detected in the urine of most volunteers. This data indicated that one time drinking of 240 mg of caffeine by healthy Indonesian volunteers did not result in urinary caffeine excretion above 12 μg.ml^-1, the upper limit permitted by the International Olympic Committee.