Pharmacokinetics of low dose sulfadiazine in patients with renal failure.

The pharmacokinetics of sulfadiazine (SD) in a lower dose (500 mg once a day, loading dose 1000 mg) than generally used was studied in patients with normal, moderately (creatinine 154--360 mumol/l) and severely (creatinine 753--1600 mumol/l) impaired renal function. In all groups SD concentrations in serum and urine were high enough for the treatment of urinary tract infections (UTI). The serum concentration of SD and metabolites showed a clear increase in severely uremic patients within 5 days. The patients showed, on the other hand, no signs of side-effects. In moderate uremia hardly any tendency towards an accumulation of SD and its metabolites was detectable during the same period of investigation. SD can thus evidently be used for the treatment of UTI with a low dose of 500 mg daily (loading dose 1000 mg), but caution should be taken in cases of impaired renal function. In moderate uremia treatment can be continued for more than one week provided that the drug concentrations in serum can be monitored. In severe uremia treatment should be limited to a period of one week.