Studies of sulfamethoxydiazine

Serum, plasma, and urine concentrations resulting from the administration of sulfamethoxydiazine, a new long‐acting sulfonamide, were studied in twelve adults. A single dose of 0.5,1.0, or 2.0 Gm. was found to produce peak serum levels of free drug of 3.6,8.0, and 13.4 mg. per 100 ml. in 6 to 8 hours. Seventy‐five per cent of the peak remained after 24 hours and 50 per cent was still present after 48 hours. About 5 per cent of the drug in the blood was in the acetylated form. Twenty‐five per cent of a dose of SMOD was excreted in the urine during the first 24 hours and 50 per cent in 48 hours; 20 to 30 per cent of the drug in the urine was acetylated. After various “loading doses,” SMOD was administered at 24 to 48 hour intervals for 7 to 10 days. The administration of an initial dose of 1.0 to 2.0 Gm. followed by 0.5 Gm. once daily produced serum concentrations of 6 to 14 mg. per 100 ml.; slightly higher levels were produced in individuals given somewhat larger “loading doses.” The accumulation of SMOD in the blood levels which followed its administration were similar to those of other long‐acting sulfonamides. No untoward effects were observed.