A study of the disposition of procaine penicillin G in feedlot steers following intramuscular and subcutaneous injection |
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| Authors: | M. G. PAPICH,G. O. KORSRUD&dagger ,J. O. BOISON&dagger ,W. D. G. YATES&dagger ,J. D. MACNEIL&dagger ,E. D. JANZEN&dagger ,R. D. H. COHEN § ,D. A. LANDRY¶ |
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| Affiliation: | *Department of Veterinary Physiological Sciences, Western College of Veterinary Medicine, Saskatoon, Canada;†Health of Animals Laboratory, Agriculture Canada, 116 Veterinary Road, Saskatoon, Canada;†Department of Herd Medicine and Theriogenology, Western College of Veterinary Medicine, Saskatoon, Canada;§Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada;¶Bureau of Veterinary Drugs, Health Protection Branch, Health and Welfare Canada, Ottawa, Ontario, Canada |
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| Abstract: | The disposition of an aqueous suspension of procaine penicillin G (300 000 U/ mL) was studied in feedlot steers. Four groups of three steers were used. Steers in groups 1 and 2 received procaine penicillin G once daily for 5 days intramuscularly (i.m.) at a dose of 24 000 U/kg (group 1) or of 66 000 U/kg (group 2). The injection on the last day was administered in the gluteal muscle. Steers in group 3 (i.m. neck injection) and group 4 [subcutaneous (s.c.) injection] each received a single dose of procaine penicillin G at a dose of 66 000 U/kg. From every animal, after the last injection in groups 1 and 2 and following the single injection in groups 3 and 4, a series of blood samples was taken at fixed time intervals. The plasma from these samples was analysed for penicillin G by a high performance liquid chromatography (HPLC) assay in order to determine the disposition of penicillin. The maximum plasma concentration (Cmax) and the area under the curve (AUC) were significantly different between groups 1 and 2, but we found no difference in the disappearance rate constant between these two groups. Group 4 single s.c. injections produced a lower mean Cmax (1.85 ± 0.27 ng/mL) than the mean Cmax (4.24 ± 1.08 μg/mL) produced in group 3 by i.m. injections into the neck muscle or the mean Cmax (2.63 ± 0.27 μg/mL) produced in group 2 by i.m. injections into the gluteal muscle. However the mean Cmax produced by i.m. injections into the neck muscles (group 3) was higher than the mean Cmax produced by i.m. injections into the gluteal muscle (group 2). Additionally, the disappearance t½, was longer (18.08 h) in group 4 following the s.c. injection and shorter (8.85 h) in group 3 following the i.m. neck injection, than the t½ following administration of the same dose i.m. into the gluteal muscle (15.96 h) in group 2. In this study, when procaine penicillin G was injected into the gluteal muscle, doses of 66 000 U/kg were necessary to produce plasma concentrations that were above a minimum inhibitory concentration (MIC) for penicillin G of 1.0 μg/mL as compared to doses of 24 000 U/kg. |
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