[Effect of feed antibiotics on ampicillin pharmacokinetics in chickens]

Experimental studies with broiler birds revealed that medicated feed (flavophospholipol, vitamyacin A, and the A-149 antibiotic in stimulative doses), offered in the course of two weeks, led to changes in the pharmacokinetic parameters of ampicillin administered i/v (in the form of ampicillin-Na) and via the crop (in the form of ampicillin-trihydrate at 30 mg/kg). It was found that the biologic half-life of ampicillin-Na was prolonged by A-149, and was shortened by vitamicin A, and to a certain extent--by flavophospholipol; the seeming volume of distribution was shown to rise by A-149, and to a certain extent--by flavophospholipol, and was lowered by vitamycin A. The biologic half-life of ampicillin-trihydrate was prolonged by all three ergotropic agents. The systematic bioavailability of ampicillin-trihydrate rose with the use of A-149, and dropped with the use of vitamycin A, and to a lower extent--with the use of flavophospholipol. On the base of the changes established in the pharmacokinetic parameters ampicillin-trihydrate was dosed for use via the drinking water as follows: 196 mg/l simultaneously with flavophospholipol in the feed, 156 mg/l--with the use of vitamycin A, 148 mg/l--when used with the A-149 antibiotic, and 216 mg/l--when administered at no medication via the feed.