Norethindrone Dosing
For contraception, norethindrone 0.35 mg is taken as one tablet daily at the same time every day, continuously without interruption between pill packs. 1
Dosing by Indication
Contraception (Progestin-Only Pill)
- 0.35 mg orally once daily at the same time each day, taken continuously 1
- Administration must be exact for maximum contraceptive effectiveness 1
- No pill-free intervals between packs 1
Acne Vulgaris (Combined Oral Contraceptive)
When norethindrone is combined with ethinyl estradiol for acne treatment:
- Teens >15 years and adults: 1 pill daily at the same time for 21 days, followed by 1 week off 2
- This formulation contains norethindrone acetate with ethinyl estradiol and ferrous fumarate 2
Heavy Menstrual Bleeding (Acute Management)
- Norethindrone taper protocol is effective for acute heavy menstrual bleeding in adolescents 3
- 78.9% of patients achieved complete cessation of bleeding within 7 days using this approach 3
- The specific taper dosing varies but typically starts at higher doses and gradually decreases 3
Endometriosis
- 2.5 mg orally once daily continuously 4
- This dose demonstrated 71% patient satisfaction at 6 months 4
- Alternative dosing of 2 mg dienogest daily showed similar efficacy with better tolerability (80% vs 58%) 4
Hormone Replacement Therapy
- 1 mg norethindrone acetate combined with 5 mcg ethinyl estradiol daily provides endometrial protection 5
- This combination significantly reduces endometrial proliferation compared to unopposed estrogen 5
Important Clinical Considerations
Pharmacokinetics
- Peak serum concentration occurs 2 hours after ingestion (18.3 ± 4.8 ng/ml) 6
- Half-life: initial rapid phase of 1.2 hours, followed by beta-phase of 8.5 hours 6
- Accumulation occurs with daily dosing, with serum levels increasing by 0.12 ng/ml per day over 21 days of treatment 6
Contraindications
- Pregnancy (Category X) 2
- Breast cancer or estrogen/progestin-sensitive cancers 2
- Active or history of thromboembolic disease 2
- Hepatic disease or hepatic adenomas 2
- Undiagnosed genital bleeding 2
Common Adverse Effects
- Irregular menstrual bleeding (most common reason for discontinuation at 54.5%) 3
- Breakthrough bleeding, amenorrhea 2
- Breast pain/tenderness 2
- Headache, depression, mood changes 2
- Nausea, abdominal pain 2
Special Populations
- Adolescents: Discontinuation rate of 48.5%, primarily due to irregular bleeding 3
- Breastfeeding: Norethindrone 0.35 mg is compatible with breastfeeding, though ethinyl estradiol combinations may have restrictions 2
- Pediatric use before menarche: Not indicated 2
Drug Interactions
Multiple significant interactions exist with antibiotics (cephalosporins, macrolides, penicillins, tetracyclines), anticonvulsants (carbamazepine, phenytoin, topiramate), HIV protease inhibitors, rifampin, St. John's wort, and many others that may reduce contraceptive efficacy 2