Comparative bioavailability of sulfamethoxazole in three formulations of cotrimoxazole suspensions

The pharmacokinetic parameters and relative bioavailability of sulfamethoxazole were estimated using three commercially available cotrimoxazole suspensions on six human volunteers. Maximum concentration in plasma was shown by product 1, i.e., 89.69+/-0.84 and were lower in products 2 and 3, i.e., 38.33+/-0.58 and 16.50+/-0.89, respectively. The time for maximum concentration was 4 hours in products 1 and 3 while it was 3.50 in product 2. There was prolonged elimination half-life of formulation 2 (7.50+/-0.94) than formulation 3 (7.43+/-0.54) while product 1 (4.54+/-0.15) showed lowest half-life. The values of absorption half-lives for formulations 1, 2 and 3 were 1.92+/-0.05. 1.80+/-0.41 and 2.78+/-0.25, respectively. The volume of distribution was highest in formulation 1 (0.9+/-0.00) lower in formulation 3 (0.40+/-0.03) and was lowest in formulation 2 (0.21+/-0.03). The values for total body clearance was lowest i.e., 0.24+/-0.00 in formulation 1, higher in formulation 2 i.e., 0.35+/-0.05 and still higher in formulation 3, i.e., 0.62+/-0.02. By taking the formulation 1, as standard (100%), the relative bioavailabilities of formulation 2 and 3 were 79.05 and 38.53%, respectively.