Disposition of Intramuscular Cefonicid in Elderly Patients

Objective: To examine the disposition of intramuscular (IM) cefonicid in elderly patients with bacterial pneumonia. Design: Pharmacokinetic study. Setting: A 620‐bed university‐affiliated long‐term care institution with its own 39‐bed acute care unit. Patients: Nine consecutive elderly patients with bacterial pneumonia treated with IM cefonicid. Measurements: Blood samples were collected on the seventh day of therapy over a 24‐hour period and analyzed by high performance liquid chromatography. Pharmacokinetic parameters (volume of distribution, half‐life, and clearance) and protein binding were calculated. Clinical outcome of IM cefonicid therapy was also noted. Results: The estimated creatinine clearance (Cl_cr) ranged from 32 to 145 mL/min. Peak cefonicid serum concentrations occurred at 0.5–1.5 hours, with a mean value of 118 ± 41 μ/mL. Cefonicid concentrations declined monoexponentially to 57 ± 16 μg/mL at 12 hours and 28 ± 14 μg/mL at 24 hours. The mean apparent distribution volume was 0.2 ± 0.07 L/kg, and the mean apparent total clearance was 15 ± 12 mL/min. The half‐life ranged from 3.1 to 38 hours. A linear correlation was noted between Cl_cr and cefonicid clearance (r = 0.99). Conclusions: Cefonicid absorption was variable among these patients, and the serum half‐life was longer than previous values noted in younger patients with similar degree of renal dysfunction. Pharmacokinetic and clinical outcome data from our study group indicate the potential role of IM cefonicid in treating elderly patients with bacterial pneumonia. 1993 The American Geriatrics Society