2000, Number 3
Vet Mex 2000; 31 (3)
In vitro antibacterial activity and bioavailability of various commercial preparations of benzylpenicillin-G, alone or combined with dihydrostreptomycin sulphate
Ocampo L, Páez D, Sumano H, Auró A
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ABSTRACTProducers of benzylpenicillin-G (BP-G) seek competitiveness not only through the actual cost/IU of activity, but also by modifying traditional powder preparations, i.e., as pre-suspended-stable suspensions. Considering the lack of stability of b-lactam antibacterials when suspended, and the different types and proportions of BP-G salts present in a given preparation, noticeable alterations in the in vitro activity and bioavailability could occur. To test these hypotheses, 3 powder preparations of BP-G, and 3 identically formulated preparations of pre-suspended BP-G, as well as a procaine-BP-G powder preparation were evaluated to determine their minimal inhibitory concentrations in various bacteria. Bioavailability was also assessed using an agar plate diffusion test to estimate the antibacterial-concentration activity (ACA) of the preparations, maximum plasma ACA (Cpmáx), and time to Cpmáx (tmáx), after one bolus IM dose. Results show that powder preparations of BP-G had greater in vitro potency than pre-suspended preparations of this antibacterial. Potency of powder preparations were at least two fold greater than the pre-suspended ones. Cpmáx values were greater when procaine BP-G was used, and minimum with the preparations containing benzathine BP-G. Preparations containing dihydrostreptomycin sulphate showed greater ACA than dihydrostreptomycin-free preparations; however, differences were not statistically significant (P › 0.05). This information may be of value to clinicians in particular when efficacy of BP-G against a given disease is borderline. These results question the concept of adding dihydrostreptomycin to BP-G preparations, and ponder procaine BP-G as the penicillin of choice for cattle.