Principles of drug dose adjustment during hemodialysis

Pharmacokinetics of ceftibuten-cis and its trans metabolite in healthy volunteers and in patients with chronic renal insufficiency

The impact of renal insufficiency on the dispositions of 300 mg of orally administered ceftibuten-cis, a new broad-spectrum oral cephalosporin, and its primary metabolite ceftibuten-trans was characterized in 30 adult subjects. Subjects were divided into five groups of six subjects each on the basis of their 24-h ambulatory creatinine clearances (CLCR). The apparent total body clearance (CLP/F; where F is absolute bioavailability) and renal clearance of ceftibuten-cis were significantly lower in subjects with end-stage renal disease (on maintenance hemodialysis; group V) and in those with severe (CLCR, 5 to 29 ml/min; group IV) and moderate (CLCR, 30 to 49 ml/min; group III) renal insufficiency than in those with mild renal insufficiency (CLCR, 50 to 80 ml/min; group II) or normal renal function (CLCR, greater than 80 ml/min; group I). A significant correlation was observed between CLCR and ceftibuten-cis CLP/F. The mean apparent steady-state volume of distribution (V beta/F) of ceftibuten-cis ranged from 0.21 to 0.24 liter/kg in subjects in group I, II, III, and IV. V beta/F was significantly greater in the group V subjects with end-stage renal disease (V beta/F, 0.39 +/- 0.27 liters/kg). These changes in V beta/F cannot be separated from possible changes in bioavailability. The maximum concentration of ceftibuten-trans in plasma was significantly higher and occurred significantly later in group IV subjects than it did in subjects in the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Problems in designing hemodialysis drug studies

A clear understanding of the pharmacokinetics of a drug and of the proper methods for calculating dialyzer clearance is essential in designing hemodialysis studies. Hemodialysis should not begin until drug distribution is complete. Institution of dialysis prior to distribution equilibrium will result in increased removal of drug compared to what would be found in the clinical setting. All methods of calculating dialyzer clearance should be compared to that using total amount of drug recovered in the bath divided by the area under the drug concentration versus time curve during dialysis. To adequately probe the effect of the artificial kidney on drug concentrations sufficient plasma samples must be drawn postdialysis to define the rebound phenomena.