N-oxidation, O-demethylation, and excretion of trimethoprim by the turtle Pseudemys scripta elegans

Pharmacokinetics of a sulphamethoxazole/trimethoprim formulation in pigs after intravenous administration

Plasma disposition, metabolism, protein binding and renal clearance of sulphamethoxazole (SMZ) and trimethoprim (TMP) were studied in four pigs after intravenous administration at a dose of 40 and 8 mg/kg, respectively. SMZ and TMP were quickly eliminated (mean elimination half-lives: 2.7 and 2.4 h, respectively). SMZ was predominantly acetylated; no hydroxy and glucuronide derivates could be detected in plasma and urine. TMP was 0-demethylated into 4-hydroxytrimethoprim (M1) and 3-hydroxytrimethoprim (M4) metabolite and subsequently extensively glucuronidated. SMZ, TMP and its M1 metabolite were excreted predominantly by glomerular filtration, while N4-acetylsulphamethoxazole and glucuronide conjugates of the M1 and M4 metabolites of TMP were actively eliminated by tubular secretion. The proportional drug percentage being present in the urine as parent compound was 13.1% for TMP and 16.0% for SMZ. The glucuronide conjugates of the M1 and M4 metabolites formed the main part (81.5%) of urinary TMP excretion pattern.

O-dealkylation and acetylation of sulphamethomidine by the turtle Pseudemys scripta elegans

The turtle Pseudemys scripta elegans acetylates and O-dealkylates sulphamethomidine. The yield of acetylation (3.1%) is about 0.7 times greater than the yield of O-dealkylation (4.3%).

O-demethylation and N4-acetylation of sulphadimethoxine by the turtle Pseudemys scripta elegans

After an oral dose of 350 mg of sulphadimethoxine, the turtle Pseudemys scripta elegans O-dealkylates sulphadimethoxine at the 2- and 6-position at 38% and 19% respectively, the 2-position being favoured. Acetylation of sulphadimethoxine and its hydroxy metabolites occurs for 57.4%.