Safer prescribing of therapeutic norethisterone for women at risk of venous thromboembolism

Abstract

High-dose (therapeutic) norethisterone was thought to be free of serious adverse effects. Doubts, however, first started to emerge in 1999 when two studies4 , 5 reported an increased incidence of venous thromboembolism (VTE) in women taking high-dose oral progestogens for therapeutic indications. No particular progestogen was named but the authors cautioned against prescribing ‘therapeutic’ doses in women at increased risk of VTE. They suggested that either the progestogen increased VTE risk or women requiring therapeutic doses of progestogens may have an inherent increased VTE risk. More recently Sundstrom et al. proposed that “menorrhagia could be a prothrombotic condition” when their nested, case-control study performed using the UK General Practice Research Database found that tranexamic acid, mefenamic acid and high-dose norethisterone were associated with an increased risk of VTE.6