Pharmacokinetics of intravenous gentamicin in healthy young-adult compared to aged alpacas.

The study objective was to evaluate the effects of age on aminoglycoside pharmacokinetics in eight young-adult (<4 years) and eight aged (≥14 years) healthy alpacas, receiving a single 6.6 mg/kg intravenous gentamicin injection. Heparinized plasma samples were obtained at designated time points following drug administration and frozen at -80°C until assayed by a validated immunoassay (QMS® ). Compartmental and noncompartmental analyses of gentamicin plasma concentrations versus time were performed using WinNonlin (v6.4) software. Baseline physical and hematological parameters were not significantly different between young and old animals with the exception of sex. Data were best fitted to a two-compartment pharmacokinetic model. The peak drug concentration at 30 min after dosing (23.8 ± 2.1 vs. 26.1 ± 2 µg/ml, p = .043) and area under the curve (70.4 ± 10.5 vs. 90.4 ± 17.6 µg hr/ml, p = .015) were significantly lower in young-adult compared to aged alpacas. Accordingly, young alpacas had a significantly greater systemic clearance than older animals (95.5 ± 14.4 and 75.6 ± 16.1 ml hr-1 kg-1 ; p = .018), respectively). In conclusion, a single 6.6 mg/kg intravenous gentamicin injection achieves target blood concentrations of >10 times the MIC of gentamicin-susceptible pathogens with MIC levels ≤2 µg/ml, in both young-adult and geriatric alpacas. However, the observed reduction in gentamicin clearance in aged alpacas may increase their risk for gentamicin-related adverse drug reactions.

Single-dose pharmacokinetics of ceftazidime and fluconazole during concurrent clinical use in cold-stunned Kemp's ridley turtles (Lepidochelys kempii).

Single-dose pharmacokinetics of intramuscularly administered ceftazidime (22 mg/kg) and subcutaneously administered fluconazole (21 mg/kg) were investigated during concurrent clinical use in naturally cold-stunned Kemp's ridley turtles (Lepidochelys kempii). Maximum mean concentration for ceftazidime was 61.31 µg/mL, and time of maximum concentration was 1.56 h postinjection. Maximum mean concentration for fluconazole was 26.16 µg/mL, and time of maximum concentration was 0.79 h postinjection. Results indicate that the ceftazidime dose and dosing interval used in this study are likely to be effective in treating susceptible strains of bacteria in Kemp's ridley turtles. However, the fluconazole dose and dosing interval are not likely to be effective against filamentous fungal pathogens that are often involved in marine turtle fungal infections.