Abstract
Pharmacological properties of sulfamethoxazole (SMX), trimethoprim (TMP) and their mixture (SMX-TMP=5 : 1) were investigated, and the following results were obtained.
1. SMX, TMP and SMX-TMP, when administered orally in rats, did not affect urine volume and urinary sugar concentration. TMP and SMX-TMP, but not SMX, increased sodium excretion and decreased potassium excretion. These actions were dose-dependent and are attributed to TMP.
2. On daily administration of TMP and SMX-TMP, the above effects were maintained, and there was no change in the plasma levels of sodium and potassium ions.
3. TMP had no effect on the blood sugar level, but high doses of SMX and SMX-TMP had a hypoglycemic action. This hypoglycemic action is probably due to SMX.
4. SMX, TMP and SMX-TMP did not inhibit the gastrointestinal propulsion of a charcoal meal in mice.
5. When administered intravenously, SMX (sodium salt), TMP (lactate) and SMX+TMP did not affect contraction of skeletal muscle in rabbits.
6. SMX (sodium salt), TMP (lactate) and SMX+TMP did not affect contraction of the isolated smooth muscle preparations.
