塩酸ドネペジルの臨床における使用の実態

薬剤師に対するアンケート調査

抄録

In Japan, the daily dose of donepezil hydrochloride (DPZ) is fixed at 3mg for 1 or 2 weeks and is to be increased to 5mg thereafter. Although the initial dose of 3mg/day has proved useful for avoiding gastrointestinal and other adverse effects, it has not proved efficacious. However, as reported to the “Internet-Based System for Sharing Pharmaceutical Case Reports” (Ohtani H., et al., YAKUGAKU ZASSHI 122 : 185-192, 2002), DPZ has also been used under irregular dosage regimens. The aim of this study was to investigate the actual usage of DPZ in clinical practice by means of an e-mail questionnaire sent to pharmacists working in medical facilities. Replies were received from a total of 194 pharmacists (17.5%). Seventyfour (38.1%) respondents said that they had seen prescriptions for DPZ with irregular dosage regimens, most of which involved administering DPZ at a dose of 3mg/day for more than a week or reducing the dose of DPZ from 5 mg/day to 3 mg/day. The primary purpose of these irregular dosage regimens was to avoid adverse reactions.
Although clinical trials have failed to prove efficacy for DPZ at a dose of 3mg/day, the results of our questionnaire imply that DPZ may actually be effective in some patients at this dose. Since irregular dosage regimens are not to be recommended, further clinical studies are needed to analyze the therapeutic effects of DPZ from the pharmacokinetic and pharmacodynamic viewpoints in order to clarify the factors of inter-patient variations in efficacy.