The pharmacokinetics of cefixime (CFIX), a new oral cephem, were examined by a repeated-dose study in 8 patients with various degrees of impaired renal function. CFIX 100mg capsules were orally administered twice a day for 6-10 days to 2 patients whose renal function was severely impaired (Ccr<30ml/min), 3 with moderate impairment (30≦Ccr<50ml/min) and 3 with slight impairment (Ccr≦50ml/min). Serum and urinary concentrations of CFIX were measured on the third or fourth and the last dosing day. Pharmacokinetic parameters based on a one-compartment open model with a time-lag in the absorption stage were calculated by the 2-line fitting method. The results obtained are summarized as follows. Serum concentrations peaked at 4 to 6 hours after dosing in all patients and the values in patients with severely impaired renal function were higher than in those with moderate or slight impairment. However, in the later patients, there was no causal relationship between serum concentration and renal function, since the absorption of the drug varied widely from patient to patient. The elimination rate of CFIX from serum tended to be low in patients with severely impaired renal function. The amount of CFIX excreted in urine did not correlate with renal function, but there was a significant correlation between renal clearance of CFIX (C1R) and Ccr (p<0.01). The elimination rate constant ke1 correlated with Ccr (p<0.10), and the following regression equation was obtained: ke1=0.0018 Ccr+0.085 Half-life (t1/2) was markedly prolonged when Ccr was lower than 30 ml/min.
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