Renal clearance fexofenadine

Drug-drug interactions involving fexofenadine have been reported which includes not only interactions with concomitant chugs, but also those with fruit juices. Concomitant use of itraconazole (303), verapamil (304), and ritonavir (305) increased the area under the curve of the plasma concentration (AUC) and peak plasma concentration (Cmax) of fexofenadine following oral administration, but did not affect the elimination half-life. Itraconazole and verapamil did not affect the renal clearance of fexofenadine, while the effect of ritonavir on the renal clearance was not examined. Considering the absence of the effect on the renal clearance, these interactions will include the inhibition of intestinal... 

Cimetidine 400 mg twice daily for 6 days did not cause any changes in the plasma pharmacokinetics of a single 120-mg dose of fexofenadine in 12 healthy subjects. However, the renal clearance of fexofenadine was decreased by 39%. ... 

A single 60-mg dose of fexofenadine was given to 24 healthy subjects 2 days before and on the last day of a 6-day course of rifampicin 600 mg daily. The oral clearance of fexofenadine was increased 1.3- to 5.3-fold, with no effect on renal clearance or half-life. This was thought to be due to the effect of rifampicin on P-glycoprotein, which is involved in the up-... 

In a detailed clinical study, it was demonstrated that both enantiomers of fexofenadine possess equal potency but differ in selected pharmacokinetic parameters [10]. A 63 37 steady-state ratio of f -(-f)-l and 5-(—)-l was observed in plasma and this remained constant across time and dosing. In a later study, it was found that the AUC and the maximum plasma concentration (Cmax) of f -(-f)-l were significantly greater than those of the 5-(—)-enantiomer [11]. Furthermore, plasma and renal clearance of oral 5-(—)-fexofenadine were both significantly greater than for the f -(-i-)-enantiomer. 

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