HYPOTHESES Is Renal Function the Only Determinant in the Elimination of Ceftazidime?

Ceftazidime is a third-generation cephalosporin that is eliminated primarily via the kidneys. Several studies have indicated that dosage adjustment is necessary in patients with renal disease. The correlation between the glomerular filtration rate and half-life (tYz) developed by Norrby and co-workers was used to evaluate, in three patients, the hypothesis that renal function is the principal determinant in excretion of the ceftazi-dime. Results obtained indicate that although the correlation appeared valid for a patient with chronic renal failure it did not predict patterns of ceftazidime elimination in two granulocytopenic patients with lymphoma. Therefore, caution should be exer-cised when employing Norrby's correlation for adjusting ceftazidime dosage for pa-tients with certain disease states. Ceftazidime is a newly developed, third-genera-tion, f3-lactamase-resistant cephalosporin for par-enteral administration. It has a broad spectrum of activity that includes Pseudomonas species and Enterobacteriaceae. It is widely used in a variety of patients, ranging from those with uncomplicated urinary tract infections to those with cystic fibrosis or with cancer and associated granulocytopenia, whose susceptibility to life-threatening infections is great [1]. The pharmacokinetics of ceftazidime appear uncomplicated because it is not metabo-lized, exhibits a low degree of binding to plasma protein, undergoes no significant nonrenal elimi-nation, is excreted by glomerular filtration, and exhibits dose proportionality for those doses commonly used in a clinical setting (levels of drug in serum are proportional to doses administered). Received for publication October 17, 1983, and in revise