Key result
Initiation of norethindrone in 3 adolescent females on stable warfarin regimens led to increased INR, requiring up to a 50% reduction in weekly warfarin dose over 5 to 12 weeks.
Why the study?
Postmenarchal adolescent females on warfarin for valvular heart disease may experience heavy menstrual bleeding managed with hormonal therapies like norethindrone, raising the possibility of a drug-drug interaction.
Does the initiation of norethindrone potentiate the anticoagulant effect of warfarin in adolescent females?
Case Report (n=3)
Does the initiation of norethindrone potentiate the anticoagulant effect of warfarin in adolescent females?
Norethindrone may significantly potentiate the anticoagulant effect of warfarin in adolescent females, necessitating close INR monitoring and aggressive dose adjustments.
Answers are grounded in this paper and cite their sources.
Norethindrone initiation may increase INR and necessitate warfarin dose reduction in adolescents; hypothesis-generating case report leaves open need for prospective confirmation.
PURPOSE: In the pediatric population, warfarin remains the recommended oral anticoagulant for valvular heart disease. Warfarin carries a risk of bleeding complications that can manifest as heavy menstrual bleeding (HMB) in postmenarchal adolescent females. As a result, these patients may be started on hormonal therapies, such as norethindrone, to suppress menstruation. SUMMARY: This case series describes a potential drug interaction between warfarin and norethindrone in 3 adolescent females with a history of mechanical mitral valve replacement who developed HMB. These patients were on stable warfarin regimens before the initiation of norethindrone and subsequently experienced increases in their international normalized ratio (INR). In response, they required an up to 50% reduction in their weekly warfarin dose over 5 to 12 weeks. CONCLUSION: These observations suggest that use of norethindrone for the management of HMB may significantly potentiate the anticoagulant effect of warfarin. Close INR monitoring and aggressive dose adjustments during initiation and discontinuation of norethindrone are recommended in patients on warfarin.
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Grapsy et al. (2022) conducted a case report in Heavy menstrual bleeding in patients with mechanical mitral valve replacement on warfarin (n=3). Norethindrone was evaluated on Increase in international normalized ratio (INR) requiring warfarin dose reduction. Initiation of norethindrone in 3 adolescent females on stable warfarin regimens led to increased INR, requiring up to a 50% reduction in weekly warfarin dose over 5 to 12 weeks.
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