Lack of oxidative pathways in the metabolism of sulphisomidine by the turtle Pseudemys scripta elegans

O‐dealkylation and acetylation of sulphamethomidine by the turtlePseudemys scripta elegans

“…As soon as a methyl group is substituted at the 2 position of the pyrimidine group in the 4-sulphanilamides, such as in sulphisomidine and sulphamethomidine, no oxidation takes place at these methyl groups (12). This situation differs completely from that in methyl-substituted 2-sulphanilamides, such as sulphamerazine and sulphadimidine (7,8).…”

“…In sulphamonomethoxine an 0-dealkylation reaction can only be carried out at the 6 position. In man and in the turtle, sulphisomidine (4-sulphanilamido-2,6-dimethylpyrimidine) undergoes no oxidation of the methyl groups at the 2 and 6 positions of the pyrimidine ring (12). Sulphamethomidine can be considered a hybrid of sulphamonomethoxine and sulphisomidine.…”

“…The rate of elimination of this group of methoxy sulphonamides is more rapid in various other species such as in the cow, the horse, and the pig, with relatively short half-lives of about 10 h (2, 4, 5). Since in man the mass balance of methoxy sulphonamides accounts for only 20% 70% of the administered dose, the possibility of an 0-dealkylation pathway is feasible (12).…”

O‐dealkylation and N4‐acetylation of sulpha‐2‐monomethoxine by the turtlePseudemys scripta elegans

“…This is the principal metabolite of these sulfonamides and probably has a preferred structure ( Figure 1). The 2 position in both compounds reacts twice as fast as the 6 position (14). Therefore the lack of 0-delkylation and Nracetylation of sulpha-2-monomethoxine was unexpected.…”

“…This is only achievable when heifers calve at a relatively young age and show high milk production levels during subsequent lactations (1,5,12,14). Contradictions about the economically optimal age at first calving have been reported.…”