Pharmacokinetics Of Oxytetracycline In The Swamp Buffalo (Bubalus Bubalis)
Hashim, Kalthum (1984) Pharmacokinetics Of Oxytetracycline In The Swamp Buffalo (Bubalus Bubalis). Masters thesis, Universiti Pertanian Malaysia.
Pharmacokinetics of oxytetracycline (OTC) was studied in swamp mg/kg buffalo heifers and cows after a single injection of OTC hydrochloride intravenously and OTC long acting 20 (LA) formulation (Terramycin/LA, Pfizer) intramuscularly using a crossover study. The concentration of OTC in serum samples was measured by a bioassay technique using Bacillus cereus (ATCC 11778) as the test organism. The disposition curve for oxytetracycline activities after intravenous administration was best described by a two-compartment open model. The serum concentrations at time zero, co'p, for buffalo cows and buffalo heifers were 61 . 37+19 . 62 mcg/ml and 33 . 09+9 . 93 mcg/ml respectively . The elimination half-lives for buffalo cows (10.13+2 . 72 h) and heifers ( 8.72+2.14 h) after intravenous injection of the drug were not significantly different ( P)0.05). The apparent volume o f distribution was significantly higher in buffalo cows ( 2.84+0 . 46 L/kg) than in heifers ( 2.0+0.42 L/kg ) but the total body clearance did not differ significantly (P>0 . 05) . Following a single intramuscular injection of OTC-LA formulation only one rate constant of absorption was noted in buffalo cows (ka1-0. 05 h) but two rate constants of absorption were noted for heifers - a fast rate ( ka1-3 . 62 h) and a slow rate ( ka2 -0. 04 h). The peak serum concentration of OTC for buffalo cows was 4 . 56+1 . 48 mcg/ml at 4.67+1.91 hours and for buffalo heifers was 4.40+ 0.57 mcg/ml at 1.67+0.26 hours.The bioavailability of OTC was 64 and 24 per cent for buffalo cows and heifers respectively . Plasma concentrations above 0.5 mcg/ml were maintained for approximately 50-60 hours . The minimum inhibition concentration (MIC) for eleven isolates from diseased buffaloes ranged from 0 . 25 to 4.0 mcg/ml . For the swamp buffalo OTC-LA is recommended at a dosing rate of 20 mg/kg injected intramuscularly at 48-hour dosage intervals for highly susceptible organisms (MIC<1 mcg/m1 ) . However it is preferable to use the conventional OTC formulation intramuscularly for less susceptible organisms (MIC>2 mcg/ml ) .
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