Figure 10 shows the cumulative percentages of patients from each treatment group with specified changes from baseline ADCS-ADL-severe scores. While both patients assigned to ARICEPT®and placebo have a wide range of responses, the curves demonstrate that the ARICEPT®group is more likely to show a smaller decline or an improvement.

Figure 10. Cumulative percentage of patients completing 24 weeks of double-blind treatment with particular changes from baseline in ADCS-ADL-severe scores.

Japanese 24-Week Study

In a study of 24 weeks duration, conducted in Japan, 325 patients with severe Alzheimer's Disease were randomized to doses of 5 mg/day or 10 mg/day of donepezil, administered once daily, or placebo. Patients randomized to treatment with donepezil were to achieve their assigned doses by titration, beginning at 3 mg/day, and extending over a maximum of 6 weeks. 248 patients completed the study with similar proportions of patients completing the study in each treatment group. The primary efficacy measures for this study were the SIB and CIBIC plus.

At 24 weeks of treatment, statistically significant treatment differences were observed between the 10 mg/day dose of donepezil and placebo on both the SIB and CIBIC plus. The 5 mg/day dose of donepezil showed a statistically significant superiority to placebo on the SIB, but not on the CIBIC plus.

Clinical Pharmacokinetics

ARICEPT® ODT is bioequivalent to ARICEPT® Tablets. Donepezil is well absorbed with a relative oral bioavailability of 100% and reaches peak plasma concentrations in 3 to 4 hours. Pharmacokinetics are linear over a dose range of 1-10 mg given once daily.

Neither food nor time of administration (morning vs. evening dose) influences the rate or extent of absorption of ARICEPT® Tablets. A food effect study has not been conducted with ARICEPT® ODT; however, the effect of food with ARICEPT® ODT is expected to be minimal. ARICEPT® ODT can be taken without regard to meals.

The elimination half life of donepezil is about 70 hours and the mean apparent plasma clearance (Cl/F) is 0.13 L/hr/kg. Following multiple dose administration, donepezil accumulates in plasma by 4-7 fold and steady state is reached within 15 days. The steady state volume of distribution is 12 L/kg. Donepezil is approximately 96% bound to human plasma proteins, mainly to albumins (about 75%) and alpha₁- acid glycoprotein (about 21%) over the concentration range of 2-1000 ng/mL.

Donepezil is both excreted in the urine intact and extensively metabolized to four major metabolites, two of which are known to be active, and a number of minor metabolites, not all of which have been identified. Donepezil is metabolized by CYP 450 isoenzymes 2D6 and 3A4 and undergoes glucuronidation. Following administration of ¹⁴C-labeled donepezil, plasma radioactivity, expressed as a percent of the administered dose, was present primarily as intact donepezil (53%) and as 6-O-desmethyl donepezil (11%), which has been reported to inhibit AChE to the same extent as donepezil in vitro and was found in plasma at concentrations equal to about 20% of donepezil. Approximately 57% and 15% of the total radioactivity was recovered in urine and feces, respectively, over a period of 10 days, while 28% remained unrecovered, with about 17% of the donepezil dose recovered in the urine as unchanged drug.

Special Populations

Hepatic Disease: In a study of 10 patients with stable alcoholic cirrhosis, the clearance of ARICEPT® was decreased by 20% relative to 10 healthy age and sex matched subjects.

Renal Disease: In a study of 11 patients with moderate to severe renal impairment (Cl_Cr < 18 mL/min/1.73 m²) the clearance of ARICEPT® did not differ from 11 age and sex matched healthy subjects.

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