Abstract
PURPOSE:
We studied the bioequivalence of a new once-daily regimen of tamoxifen citrate relative to the standard twice-daily regimen of tamoxifen citrate, an established antiestrogenic treatment for breast cancer.
PATIENTS AND METHODS:
Of 30 women with breast cancer, 27 completed this open, two-period, crossover randomized trial. During one 3-month period, patients took one standard 10-mg tamoxifen tablet twice daily; during the preceding or following 3-month period, patients took one of the new 20-mg tablets once daily. Pharmacokinetic profiles and safety parameters were assessed at the end of each 3-month treatment period.
RESULTS:
Overall, measured concentrations of tamoxifen and its principal active metabolite, N-desmethyltamoxifen, remained relatively constant over the 24-hour sampling periods at the end of each treatment sequence. For both compounds, the percentage differences of the geometric means for all pharmacokinetic parameters indicated bioequivalence of the once-daily regimen of tamoxifen relative to the standard twice-daily regimen. Both treatment sequences were well tolerated; reported adverse events occurred at similar frequencies with the two treatment regimens.
CONCLUSION:
The 20-mg tamoxifen tablet taken once daily was bioequivalent to the 10-mg tamoxifen tablet taken twice daily, with no difference in relative risk. The once-daily treatment is a simpler regimen and may facilitate compliance, which may enhance therapeutic outcomes during long-term treatment of breast cancer.
Reference:
- J Clin Oncol 1994 Jun;12(6):1337.
- http://jco.ascopubs.org/content/12/1/50.abstract