[In vivo kinetics of cotrimoxazole in alveolar macrophages]

The aim of this work was to study the kinetic of intramacrophage penetration of cotrimoxazole in guinea pigs which had received 100 mg/kg of sulfamethoxazole and 20 mg/kg of trimethoprim after a single intraperitoneal injection. 30 minutes, 1, 3, 6 and 24 hours after this injection an intra-cardiac blood sample was taken and pulmonary lavage was performed immediately after sacrificing the animal by cervical cord dislocation. The level of trimethoprim and sulfamethoxazole was measured in each sample by high performance liquid chromatography (HPLC). An estimation of the dilution of the supernatant was obtained by comparing the supernatant glucose with the serum glucose. The serum kinetics of trimethoprim and sulfamethoxazole progressed in a parallel fasion with time with a maximal concentration at 30 minutes (for trimethoprim: 6.7 +/- 0.9 micrograms/ml and for sulfamethoxazole 176.1 +/- 16.2 micrograms/ml). On the other hand their penetration capacity was different in the supernatant and in the alveolar macrophages: the maximal concentrations were obtained after one hour in the supernatant and after 3 hours in the cellular extract and were respectively for trimethoprim 0.43 +/- 0.07 microgram/ml and 20.9 +/- 8.06 micrograms/ml of intramacrophage water and for sulfamethoxazole 1.86 +/- 0.24 micrograms/ml and 23.8 +/- 12.7 micrograms/ml of intramacrophage water. A concentration around six times greater was noted for the trimethoprim inside the cells compared with serum and was only 0.25 time for sulfamethoxazole. On the other hand the supernatant/serum ratio showed a greater concentration for trimethoprim (4 to 10) than for sulfamethoxazole (0.6 to 1).(ABSTRACT TRUNCATED AT 250 WORDS)