DEPLETION OF PENICILLIN-G RESIDUES IN TISSUES, PLASMA AND INJECTION SITES OF MARKET PIGS INJECTED INTRAMUSCULARLY WITH PROCAINE PENICILLIN-G

Procaine penicillin G was administered by intramuscular (IM) injection to groups of healthy 100 kg market pigs at the approved label dose (1 5000 IU/kg body weight), once daily for three consecutive days; or an extra-label dose (66000 IU/kg body weight), once daily for Jive consec utive days. Penicillin G residue depletion was followed in plasma, tis sue and injection sites using a liquid chromatographic method. Groups of pigs were killed 1, 2, 3, 4, 5 and 8 days after the last injection with the label dose. Penicillin G was not detected in liver after I da y of withdrawal, in muscle and fat after 2 days of withdrawal, in plas ma after 4 days of withdrawal, in skin after 5 days of withdrawal, or in kidney and the injection sites after 8 days of withdrawal. Other gr oups of pigs were killed 1, 2, 3, 5 and 7 days after injection with th e extra-label dose. In these pigs penicillin G was not found in liver after 2 days of withdrawal, in fat after 3 clays of withdrawal, or in the muscle, skin, plasma and injection sites after 7 days of withdrawa l. Penicillin G was found at all times in the kidneys of the groups of pigs that received the high dose. The technique used for neck injecti ons was critical to obtain intramuscular rather than intermuscular inj ections. The Bureau of Veterinary Drugs, Health Protection Branch, Hea lth Canada calculated that the appropriate withdrawal period for pigs was 8 days for a dose of 15 000 IU procaine penicillin G/kg body weigh t and 15 days for a dose of 66 000 IU/kg.