An information note agreed between the European regulatory authorities and AIFA (the Italian medicines agency) reports the results of a retrospective study,
according to which the risk of venous thromboembolism (VTE) is slightly increased in women using combined hormonal contraceptives based on chlormadinone acetate and ethinylestradiol.
The conclusion comes from the retrospective cohort study RIVETRCS, according to which the risk of venous thromboembolism increases 1.25-fold with this type of contraceptive compared to women taking combined hormonal contraceptives containing levonorgestrel. Based on these results, the annual risk of VTE in women taking chlormadinone acetate with ethinylestradiol is estimated at 6-9 cases of VTE per 10,000 women.
These data are compared with an annual incidence of 5-7 VTE cases per 10,000 women using low risk combined hormonal contraceptives containing levonorgestrel, norethisterone or norgestimate, and with 2 VTE cases per 10,000 women not using a combined hormonal contraceptive.
The decision to prescribe a combined hormonal contraceptive must therefore take into account the individual woman’s risk factors for VTE and be based on a comparison with the VTE risk of other combined hormonal contraceptives. AIFA also points out that the risk is highest during the first year of use of any combined hormonal contraceptive or upon resumption of treatment with combined hormonal contraceptives after a break of 4 weeks or more.