First-use risks

Caution is always required in prescribing estrogen-progestin combinations, whether for contraception, postmenopausal hormone replacement or treatment of acne. However, the risk attributed to preparations containing cyproterone acetate in comparison with other preparations may have been exaggerated by not taking first-time use into account. This effect has been estimated2 to increase the risk of venous thromboembolism 10-fold in the first year of oral contraceptive use, regardless of preparation. The research letter of Vasilakis-Scaramozza and Jick,3 which was used by Health Canada to support the increased risk, provided adjusted odds ratios for venous thromboembolism, but no reference is made to first-time use as a potential factor.