ELIMINATION OF RESIDUES AND TISSUE-DAMAGE AFTER INTRAMUSCULAR INJECTION OF A COMBINATION OF TRIMETHOPRIM AND SULPHATROXAZOLE

Two different studies are described. The first study deals with the el imination of residues of trimethoprim (TMP), sulphatroxazole (STX) and its main metabolite N-4-acetyl-sulphatroazole (N-4-acetyl-STX) in pig s. Thirty-six pigs were treated with trimethoprim/sulphatroxazole(1) I M in the neck at a dosage of 16 mg/kg body weight for five day's. Grou ps of four pigs were slaughtered at different time intervals. The stud y showed that concentrations of STX, N-4-acetyl-STX and TMP in edible tissues and at the injection sites were below 0.1 ppm on day nine afte r the last injection. STX was eliminated the slowest, and STX can ther efore be selected as a marker for residues of the trimethoprim/sulfatr oxazole formulation in the tissues. The second study deals with irrita tion aspects of this trimethoprim/sulfatroxazole(1) formulation. Four pigs of 32-35 kg were treated IM with trimethoprim/sulphatroxazole and benzylpenicillin sodium(3). Each pig received the same injection volu me, namely four trimethoprim/sulphatroxazole injections (16 mg/kg body weight per injection site), two in the back and two in the neck muscl e, and two benzylpenicillin sodium injections (20.000 I.U./kg body wei ght per injection site), in the back muscle. All pigs were slaughtered 14 days after treatment and the extent of irritation was compared. Th ere were no differences between trimethoprim/sulfatroxazole and benzyl penicillin sodium with regard to irritation at the injection site in t he back muscle. The irritation in;he neck was statistically less promi nent than that in the back muscle and was considered not to affect the quality of the meat.