Biperiden pharmacokinetics

AChs are an effective treatment (see Table 71-4). Benztropine has a half-life that allows once- to twice-daily dosing. Dose increases above 6 mg/day must be slow because of nonlinear pharmacokinetics. Trihexyphenidyl, diphenhydramine, and biperiden usually require three-times-daily dosing. Diphenhydramine produces more sedation, but all of the AChs have been abused for euphoriant effects. 

Pharmacokinetic and pharmacodynamic profiles of olanzapine have been extensively reviewed (266). Olanzapine does not inhibit CYP isozymes, and no clinically significant metabolic interactions were found of olanzapine with aminophylline, biperiden, diazepam, ethanol, fluoxetine, imipramine, lithium, or R/S-warfarin. 

Isawa S, Murasaki M, Miura S, Yoshioka M, Uchiumi M, Kumagai Y, Aoki S, Hisazumi H, Kudo S. Pharmacokinetic and pharmacodynamic interactions among haloperidol, carteolol hydrochloride and biperiden hydrochloride. Nihon Shinkei Seishin Yakurigaku Zasshi 1999 19(3) 111-18. 

A pharmacokinetic study in 10 patients found that fluoxetine 20 mg daily raised the levels of risperidone 2 or 3 mg twice daily from 12 to 19 nanograms/mL after 3 weeks and to 56 nanograms/mL after 4 weeks. All patients experienced a rise in risperidone levels, but this varied from two to tenfold. One patient withdrew from the study because of severe akathisia and another two patients needed treatment with biperiden to control parkinsonian adverse effects. Similar findings were found in another study. ... 

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