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Progestin-Only Pill (Norethindrone)

Hormonal Contraceptiveprescriptionoral · inferred

Progestin-only minipill containing norethindrone 0.35 mg. Short half-life (~8h) requires strict same-time daily dosing (3-hour window). Brands: Micronor, Camila, Errin. Works primarily by thickening cervical mucus. Safe for breastfeeding and smokers over 35.

Projected serum levels — 1 pill (≈ 0.35 mg), once daily

Progestin-Only Pill (Norethindrone)
Progestin-Only Pill (Norethindrone) modeled serum levels, 1 pill (≈ 0.35 mg) once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 0.25 0.50 0.75 1 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1

Maintenance schedule: 1 pill (≈ 0.35 mg) once daily (oral).

Modeled steady state after ~1 days: peak ≈ 0.22 mg, trough ≈ 0.034 mg body load. Population-based estimate over 15 days for a reference dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Hormonal Contraceptive
Route modeled
Oral
Model confidence
inferred
Half-life
8 h
Common dose
1 pill (≈ 0.35 mg)
Suggested maximum
1 pill/day
Reference dose range
0.50–1 pill (single dose)
Suggested cadence
once daily
Validated against
0.35 mg oral — Cmax 0.004 mg/L at 2 h

Documented interactions

  • contraindicated
    Efavirenz (Sustiva) + Progestin-Only Pill (Norethindrone) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Progestin-Only Pill (Norethindrone) AUC by ~0.15x

  • contraindicated
    Rifampin + Progestin-Only Pill (Norethindrone) CYP induction

    Rifampin inducer of CYP3A4 predicted to change Progestin-Only Pill (Norethindrone) AUC by ~0.15x

  • danger
    Amlodipine (Norvasc) + Progestin-Only Pill (Norethindrone) CYP inhibition

    Amlodipine (Norvasc) reversible_inhibitor of CYP3A4 predicted to change Progestin-Only Pill (Norethindrone) AUC by ~2.36x

  • danger
    Ashwagandha (KSM-66) + Progestin-Only Pill (Norethindrone) CYP inhibition

    Ashwagandha (KSM-66) reversible_inhibitor of CYP3A4 predicted to change Progestin-Only Pill (Norethindrone) AUC by ~2.36x

  • danger
    Berberine + Progestin-Only Pill (Norethindrone) CYP inhibition

    Berberine reversible_inhibitor of CYP3A4 predicted to change Progestin-Only Pill (Norethindrone) AUC by ~2.36x

  • danger
    Black Seed Oil (Nigella sativa / Thymoquinone) + Progestin-Only Pill (Norethindrone) CYP inhibition

    Black Seed Oil (Nigella sativa / Thymoquinone) reversible_inhibitor of CYP3A4 predicted to change Progestin-Only Pill (Norethindrone) AUC by ~2.36x

Serum checks 111 modeled interaction pairings for progestin-only pill (norethindrone) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Progestogen-Only Contraceptives: Current Evidence and Practice Glasier A · Best Practice & Research Clinical Obstetrics & Gynaecology, 2002 DOI

    Comprehensive review of progestin-only methods covering mechanism, efficacy, pharmacokinetics, and clinical considerations for the minipill.

  2. The Pharmacokinetics of Norethisterone and Ethinylestradiol in Relation to the Menstrual Cycle Back DJ et al. · Contraception, 1978 DOI

    Established norethindrone pharmacokinetic parameters showing rapid absorption (Tmax 1-2h), 64% bioavailability, and 5-13 hour half-life.

  3. Efficacy, Safety, and Personal Experience with Norethindrone 0.35 mg Progestogen-Only Pill McCann MF, Potter LS · American Journal of Obstetrics and Gynecology, 1994 DOI

    Meta-analysis of minipill efficacy showing 0.5% perfect-use failure rate and importance of strict timing adherence for the short-acting formulation.

3 published studies referenced in the app, each with a plain-language summary.