Effect of age and renal function on cefonicid pharmacokinetics

Cefonicid (15 mg/kg) was administered intravenously at a constant rate of infusion over 15 min to 10 geriatric patients (mean age, 77 years) and to 4 young subjects (mean age, 35 years). Model-dependent and noncompartmental pharmacokinetic parameters were calculated and found to be congruous; noncompartmental data are reported. Significant differences in the values for area under the curve, mean residence time, total body clearance, and renal clearance were observed between the geriatric and young groups. Mean elimination half-life values were 9.59 and 4.88 h for the geriatric and young groups, respectively. Total body and renal clearances were inversely correlated to age and directly correlated to creatinine clearance. Free fraction was not correlated to albumin concentration but was correlated exponentially to total cefonicid concentration. Despite the prolonged half-life values observed in our geriatric patients, the difference in mean trough concentrations was slight. Daily administration of a 15-mg/kg dose should provide adequate concentrations in serum and should not produce appreciable accumulation in geriatric patients.