delaying menstruation

Last reviewed 07/2023

This can be achieved by the use of norethisterone 5mg three times daily starting 3 days before the anticipated onset of menstruation. Menstruation will occur 2-3 days after stopping taking the norethisterone (NET).

Notes:

• a study by Kuhnz et al has demonstrated that NET is partly metabolised to ethinyl - estradiol (EE) which is why it is so effective at postponing menstruation. The equivalence is believed to be 1mg NET metabolises to 4 - 6mcgs EE (most combined oral contraceptives contain 20 - 30mcgs/day EE)
  
  
  • the relevance of this in practice is that NET is often used in women who are at risk of venous thromboembolism (VTE) and are unable to use combined hormonal contraception because of their risks (2)
    • in these women the clinician should transfer prescribing to Medroxyprogesterone acetate (Provera®) 10mgs bd or tds to delay their menstruation
      
      
  • use Medroxyprogesterone acetate 10mgs bd or tds instead of NET particularly in women who are overweight, smokers, aged over 35 or any other woman at risk of VTE (2)

Reference:

• Kuhnz W, Heuner A, Humpel M. In vivo conversion of n orethisterone acetate to ethinylestradiol in postmenopausal women. Contraception. 1997;56:379
• Mansour D. Safer prescribing of therapeutic norethisterone for women at risk of venous thromboembolism. J Fam Plann Reprod Health Care 2012;38:148 - 9
• Primary Care Women's Health Forum (July 2013). e-update.