Somnolence donepezil

Possible interactions between donepezil and risperidone, which are both metabolized by CYP2D6 and CYP3A4, have been studied (SEDA-26,65) (247). Of 24 healthy men (mean age 40 years) were assigned to risperidone 1 mg/day, donepezil 5 mg/day, or both, 20 reported at least one adverse event, mostly headache, nervousness, or somnolence. However, measures of pharmacokinetics showed no interaction. 

Seven elderly patients with psychotic or non-psychotic behavioral symptoms in Lewy body dementia had some benefit from donepezil (24). Donepezil was withdrawn prematurely in three patients owing to poor response and/or adverse events. The adverse events were sedation, somnolence, worsening of chronic obstructive pulmonary disease, syncope, sweating, and bradycardia. These results have to be confirmed in controlled trials. 

An open comparison of donepezil and risperidone, alone or in combination, in 24 healthy men showed no significant pharmacokinetic differences (88). Adverse events such as headache, nervousness, and somnolence were minor and comparable in all groups. These results suggest that no clinically significant interactions occur between risperidone and donepezil at steady state. However, whether these conclusions can be extrapolated to the elderly patients with dementia, who may eliminate both donepezil and risperidone slowly, is uncertain. 

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