A multiple once daily dose pharmacokinetic of amikacin in cow calves following intravenous administration

A multiple once daily dose pharmacokinetic of amikacin (@ 10 mg/kg, i.v.) was carried out in healthy cow calves weighing between 80-100 kg. Concentrations of amikacin in blood plasma were estimated by microbiological assay techniques as well as various kinetic parameters were calculated by using two compartment open model for amikacin. Serial blood samples were taken on days 1 and 5 of treatment and at predose, 1 and 6 h on days 2, 3 and 4. Attempts were made to calculate the rational dosage regimens of amikacin on first and last dosing, on the basis of kinetic data and maintenance of therapeutic concentrations in plasma. Amikacin was administered separately in each of four healthy calves by intravenous (i.v) route once daily for five days. The drug was detectable up to 10 h. The minimum therapeutic concentration (≥ 1.0 μg/ml) of amikacin was maintained up to 2 h in both 1^st and 5^th day of amikacin administration. Significantly higher plasma concentrations of the drug appeared from 0.042 to 6 h except 0.25 h in 5^th day of amikacin administration as compared to 1st day amikacin administration. Mean trough amikacin plasma concentrations were 0.3, Significantly higher values of extrapolated zero time concentration of the drug during distribution phase (A), theoretical zero time concentration (C_p^o), area under curve (AUC), area under first moment curve (AUMC), mean residential time (MRT) and elimination of drug from central compartment (Kel) while significantly lower value of elimination rate constant (β]) and total body clearance (Cl_B) are observed in 5^th day of amikacin administration as compared to 1st day of amikacin administration. All other kinetic parameters differ non-significantly between 1_st and 5_th day of amikacin administration. It is concluded that once-daily administration of amikacin may provide adequate plasma levels to treat most susceptible gram-negative infections in cow calves.