Comparison of pharmacokinetics of sulphadiazine and sulphamethoxazole after intravenous infusion.

The pharmacokinetics of sulphadiazine/trimethoprim (1000 mg/320 mg) and sulphamethoxazole/trimethoprim (1000 mg/200 mg) were compared in a cross-over study after intravenous infusion of the drugs over a 60 min period to six young, healthy volunteers. Serum protein bindings of sulphadiazine and sulpha-methoxazole were 50 and 71%, elimination half-lives were 7·0 and 7·9 h, apparent distribution volumes were 0·29 and 0·21 1/kg (<0 05 total clearances were 0·55 and 0·31 ml/min/kg (<0.05) and AUC values were 510 and 795 mg/l×h (<0.01), respectively. The total 48-h recovery of sulphadiazine was 71·8% of the dose and 62% of the dose was excreted as active drug in urine. With sulphamethoxazole, the total recovery was 78·6% and only 23% of the dose was excreted unmetabolized. Protein binding of trimethoprim was 42–46%, its half-life was 9·4–10·7 h, the distribution volume was 1·35 1/kg and the total clearance was 1·41– ml/min/kg. It is concluded that sulphadiazine is pharmacokinetically superior to sulphamethoxazole, since it is less bound to serum proteins, its distribution volume is larger and it gives higher concentrations of active sulphonamide in serum and urine. [ABSTRACT FROM PUBLISHER]