Duration of Secretion of Bacteriostatic Drugs in Milk. I. Penicillin, Following Oral and Parenteral Administration

Abstract

Summary The duration and concentration of penicillin in milk were determined following intramuscular and oral administration of procaine penicillin G in sesame oil with 2% aluminum monostearate and intramuscular, intravenous, and intrauterine administration of potassium penicillin G in aqueous suspension. Following intramuscular injection at the rate of 3,000 units per lb of body weight, the maximum interval that penicillin was detected in the milk of the test animals was 96 hr for cows that received penicillin in oil, and 72 hr for those that received aqueous penicillin. Milk from only 25% of the cows in both groups contained detectable penicillin at the maximum intervals. Intravenous injection of 2,000 units of aqueous penicillin per pound of body weight yielded detectable penicillin in the milk of 25% of the test animals at 20 hr, and in 8.3% at 44 hr post-injection. Penicillin was found in the milk of 16.7% of the test animals 27 to 31 hr after intrauterine infusion of 1,000,000 units of aqueous penicillin, and at subsequent intervals no penicillin was detected in milk from any of the cows. A single dose of 10,000,000 units of penicillin in oil fed with concentrate resulted in detectable penicillin in the milk a maximum of 86 hr post-feeding, at which time only 8.3% of the samples were positive. Correlations between the duration of secretion of milk containing penicillin and milk production, fat content of the milk, and body weight were nonsignificant (P > .05) for all methods of administration.