Both norethisterone and Provera (medroxyprogesterone acetate) are similarly effective for controlling heavy menstrual bleeding, with cyclic oral progestin treatment reducing bleeding by approximately 87%, though neither is first-line therapy.
Evidence-Based Comparison
Both medications demonstrate comparable efficacy when used in appropriate regimens for heavy menstrual bleeding. The 2011 AACE guidelines list both medroxyprogesterone acetate (2.5 mg daily or 5 mg for 10-12 days/month) and norethindrone acetate (0.35 mg daily or 5 mg for 10-12 days/month) as acceptable progestational agents that provide endometrial protection 1. The 2018 AHA scientific statement notes that cyclic oral progestin treatment reduces bleeding by 87% and generally results in irregular bleeding with reduction of menses to only light bleeding 2.
Key Clinical Considerations
Dosing Regimens
- Provera (medroxyprogesterone acetate): 5-10 mg daily for 5-10 days for abnormal uterine bleeding 3
- Norethisterone: 5-10 mg three times daily from day 5-25 (long cycle) or day 12-25 (short cycle) of the menstrual cycle 4
Comparative Performance
Research evidence shows neither agent is superior to other medical therapies. A 1990 study demonstrated both norethisterone and medroxyprogesterone acetate effectively reduced measured menstrual blood loss in both anovulatory and ovulatory women, though three women with ovulatory dysfunction did not respond 4.
More importantly, both oral progestogens are inferior to:
- Levonorgestrel-releasing intrauterine system (71-95% reduction in menstrual blood loss) 2
- Tranexamic acid 5, 6
- Endometrial ablation techniques 5, 7
Side Effect Profile
Both medications share similar progestational side effects including 1:
- Premenstrual-tension-like symptoms
- Mood swings, bloating, fluid retention
- Sleep disturbance
- Breakthrough bleeding
- Weight changes
The key difference: Individual women may tolerate one progestogen better than another due to variations in androgenic potency, glucocorticoid activity, and effects on lipids, insulin sensitivity, and blood pressure 1.
Clinical Algorithm
For a reproductive-age woman with heavy menstrual bleeding:
First-line: Consider levonorgestrel-IUS (most effective, 71-95% reduction) 2
If IUS declined or contraindicated: Choose either norethisterone or Provera based on:
- Contraindications: Check for undiagnosed vaginal bleeding, breast cancer history, thromboembolic disease, liver disease 3
- Patient preference: Some women prefer twice-weekly dosing (norethisterone) vs. daily (Provera)
- Cost and availability: Local formulary considerations
Trial period: Use for 3-6 months, then reassess 3
If treatment fails: Consider switching progestogens first (may improve tolerability), then escalate to tranexamic acid, LNG-IUS, or surgical options 8, 5
Important Caveats
- Cardiovascular disease patients: These women should generally avoid oral progestogens; transdermal or IUS options are preferred 2
- Treatment failure is common: Up to 3 of 10 women with ovulatory dysfunction may not respond adequately 4
- Long-term use: Both require periodic reassessment every 3-6 months 3
- Not for acute hemorrhage: For hemodynamically unstable bleeding, high-dose oral or injectable progestin-only medications may be needed short-term 2
The bottom line: Choose either medication based on patient-specific factors (contraindications, tolerability, dosing preference), but recognize both are second-line options with similar efficacy around 87% reduction in bleeding. If either fails after 3-6 months, escalate to more effective therapies rather than switching between oral progestogens.