A patient who received a labeled dose of 10 mg of donepezil per day for 3 months that was purchased from Canada could have been receiving only 6.3 mg per day..



Wang, Chong-Zhi; Du, Guang-Jian; Zhen, Zhong; Calway, Tyler; Yuan, Chun-Su(2011) Significant Dose Differences in Donepezil Purchased From the United States and Canada
Annals of Internal Medicine
Issue: Volume 155(4), 16 August 2011, pp 279-280

Methods: We purchased brand-name donepezil tablets […]. We also purchased brand-name donepezil tablets from a hospital pharmacy in China in a package labeled “Eisai, China.” Using an Internet search engine, we selected 3 drugstores in Canada […] We placed 5 prescription orders at these stores between March 2010 and September 2010 and received packages from India […].

We measured the dose of donepezil in tablets using high-performance liquid chromatography […]

Findings: The ultraviolet spectra on high-performance liquid chromatography of all tablets from the United States, China, and Canada were similar to the donepezil standard, which indicated that the tested samples had the same chemical structure. Donepezil tablets purchased from the United States and China contained the dose that was on the label (99.6% and 101.0%, respectively). In contrast, the 5 orders of generic donepezil tablets from Canada contained only 58.4% to 67.1% of the dose on the label (P < 0.01, paired t test)