Levonorgestrel

Progestin·Endocrinology - Women's Health

Emergency contraception, continuous contraception, heavy menstrual bleeding (Mirena)

PBSHORMONEPostinor-1, Levonelle (Emergency). Microlut (Mini-Pill). Mirena (IUD).1.5 mg tabletS4+1

Emergency Dose

1.5 mg STAT

Half-life

24 h

BMI > 70kg

DOUBLE DOSE

VTE Risk

SAFE

Rapid Summary

Overview

Potent, highly stable synthetic progestogen. Used as the 'Morning After Pill', the active hormone in the Mirena IUD, and the 'Mini-Pill'. Thickens cervical mucus and halts ovulation.

Maximum Dose

Max 1.5 mg STAT (Emergency Contraception) or 3 mg STAT (if BMI > 26 or taking enzyme inducers).

Clinical Focus

Extremely safe regarding cardiovascular/clotting risk. The emergency contraceptive pill must be taken within 72 hours of unprotected intercourse.

Bottom Line

Levonorgestrel is used in progestogen-only pills, IUDs, and emergency contraception, but the emergency dose must be taken within 72 hours and efficacy decreases significantly with delay.

Formulation & Access

Brand Names

Postinor-1, Levonelle (Emergency). Microlut (Mini-Pill). Mirena (IUD).

Oral Routes

Tablets (1.5 mg, 30 mcg).

Prescribing & PBS

Emergency Contraception is Over The Counter (S3). IUD/Mini-Pill is S4.

Indications & Use

Primary

PBSTGA

Emergency contraception, continuous contraception, heavy menstrual bleeding (Mirena).

Clinical Place

The Mirena IUD is the absolute gold standard for treating heavy/painful periods and providing highly reliable, 'forget-proof' contraception.

Quick reference

Class & Role

Progestin — Potent, highly stable synthetic progestogen.

Route / Formulation

Tablets (1.5 mg, 30 mcg). (Postinor-1, Levonelle (Emergency). Microlut (Mini-Pill). Mirena (IUD).)

Usual Dose & Max

PO 1.5 mg STAT (Take ASAP, up to 72 hours post-intercourse). Max 1.5 mg STAT (Emergency Contraception) or 3 mg STAT (if BMI > 26 or taking enzyme inducers).

Key Indication Doses

Emergency Contraception: PO 1.5 mg STAT (Take ASAP, up to 72 hours post-intercourse). Heavy BMI (>70kg / BMI >26): PO 3 mg STAT (Take two 1.5mg tablets together). The standard dose fails in heavier patients. Progestogen-Only Pill (Mini-Pill): PO 30 mcg OD (Must be taken at the EXACT same time every day. If > 3 hours late, effectiveness drops to zero). Intrauterine Device (IUD): Mirena (52 mg) releases 20 mcg/day continuously for 5 years directly into the uterus.

Best Uses

Levonorgestrel is used in progestogen-only pills, IUDs, and emergency contraception, but the emergency dose must be taken within 72 hours and efficacy decreases significantly with delay.

Avoid / Cautions

Known/suspected pregnancy, active breast cancer, severe liver disease or liver tumours, and unexplained vaginal bleeding need review before use. For emergency contraception, efficacy falls with delay, higher body weight, and enzyme-inducing medicines.

Key Risks

Gastrointestinal: Nausea/Vomiting (Common with the massive 1.5mg emergency dose. If the patient vomits within 2 hours, they MUST take another dose). Gynecological: Irregular, unpredictable spotting/bleeding (especially in the first 3-6 months of Mirena or Mini-pill use). Cardiovascular: Unlike estrogen, levonorgestrel does NOT increase the risk of DVT, PE, or stroke.

Key Interactions

Enzyme Inducers (Carbamazepine, Phenytoin, Rifampicin, St John's Wort). Destroy blood levels of oral levonorgestrel. If a patient on Epilepsy meds needs the Morning After Pill, you MUST double the dose to 3 mg STAT, or use a Copper IUD.

Monitoring

Warn patients taking the 30mcg Mini-Pill that they have a strict 3-hour window. Taking it at 8 AM one day and 12 PM the next means they are completely unprotected. No specific routine laboratory tests required.

Clinical Pearl

Levonorgestrel emergency contraception works by delaying ovulation. If the woman has *already* ovulated this cycle before having unprotected sex, the pill will 100% fail. Ulipristal (EllaOne) or a Copper IUD are better options if ovulation is imminent.

Access

Postinor-1, Levonelle (Emergency). Microlut (Mini-Pill). Mirena (IUD).1.5 mg tablet

Brand: Postinor-1, Levonelle (Emergency). Microlut (Mini-Pill). Mirena (IUD).
Formulation: Tablets (1

Levonorgestrel

Progestin·Endocrinology - Women's Health

Emergency contraception, continuous contraception, heavy menstrual bleeding (Mirena)

PBSHORMONEPostinor-1, Levonelle (Emergency). Microlut (Mini-Pill). Mirena (IUD).1.5 mg tabletS4+1

Emergency Dose

1.5 mg STAT

Half-life

24 h

BMI > 70kg

DOUBLE DOSE

VTE Risk

SAFE

Rapid Summary

Overview

Potent, highly stable synthetic progestogen. Used as the 'Morning After Pill', the active hormone in the Mirena IUD, and the 'Mini-Pill'. Thickens cervical mucus and halts ovulation.

Maximum Dose

Max 1.5 mg STAT (Emergency Contraception) or 3 mg STAT (if BMI > 26 or taking enzyme inducers).

Clinical Focus

Extremely safe regarding cardiovascular/clotting risk. The emergency contraceptive pill must be taken within 72 hours of unprotected intercourse.

Bottom Line

Levonorgestrel is used in progestogen-only pills, IUDs, and emergency contraception, but the emergency dose must be taken within 72 hours and efficacy decreases significantly with delay.

Formulation & Access

Brand Names

Postinor-1, Levonelle (Emergency). Microlut (Mini-Pill). Mirena (IUD).

Oral Routes

Tablets (1.5 mg, 30 mcg).

Prescribing & PBS

Emergency Contraception is Over The Counter (S3). IUD/Mini-Pill is S4.

Indications & Use

Primary

PBSTGA

Emergency contraception, continuous contraception, heavy menstrual bleeding (Mirena).

Clinical Place

The Mirena IUD is the absolute gold standard for treating heavy/painful periods and providing highly reliable, 'forget-proof' contraception.

Quick reference

Class & Role

Progestin — Potent, highly stable synthetic progestogen.

Route / Formulation

Tablets (1.5 mg, 30 mcg). (Postinor-1, Levonelle (Emergency). Microlut (Mini-Pill). Mirena (IUD).)

Usual Dose & Max

PO 1.5 mg STAT (Take ASAP, up to 72 hours post-intercourse). Max 1.5 mg STAT (Emergency Contraception) or 3 mg STAT (if BMI > 26 or taking enzyme inducers).

Key Indication Doses

Best Uses

Levonorgestrel is used in progestogen-only pills, IUDs, and emergency contraception, but the emergency dose must be taken within 72 hours and efficacy decreases significantly with delay.

Avoid / Cautions

Key Risks

Key Interactions

Monitoring

Clinical Pearl

Access

Postinor-1, Levonelle (Emergency). Microlut (Mini-Pill). Mirena (IUD).1.5 mg tablet

Brand: Postinor-1, Levonelle (Emergency). Microlut (Mini-Pill). Mirena (IUD).
Formulation: Tablets (1