Effect of caffeine on sulfamethazine N-acetylation and urinary excretion in healthy volunteers

ABSTRACT

The aim of the present work has been to study the influence of caffeine on the gastrointestinal absorption as well as the elimination of sulfamethazine following their concomitant oral administration in man. Five healthy volunteers [2 males and 3 females] participated in the study. Sulfamethazine was orally given in the does of 1 g either alone or preceded by 100 mg caffeine. Urinary excreted amounts of sulfamethazine and N-acetylsulfamethazine were determined at different time intervals during at least 36 hours. The following pharmacokinetic parameters were computed for sulfamethazine and its N- acetyl derivative in each individual Cumulative amount excreted, urinary excretion rate, Cmax, Tmax, rate constant of elimination and AUC. The obtained data showed that the effect of caffeine on the gastrointestinal absorption of sulfamethazine is individual-dependent. Significant decrease in absorption occurred in 3 volunteers. The extent of N-acetylation was not affected. The obtained findings are discussed in view of the pharmacodynamics of caffeine as well as the possible pharmacotherapeutic consequences