Mirena (Levonorgestrel)

• Mirena, a levonorgestrel-releasing intrauterine system, is used in several gynecologic conditions.
• Contraception (up to 5 years): provides highly effective, reversible birth control for women seeking long‑acting contraception.
• Heavy menstrual bleeding: reduces menstrual blood loss and improves anemia associated with excessive bleeding.
• Endometriosis‑associated pain: alleviates chronic pelvic pain related to endometriosis.

• Levonorgestrel released from the intrauterine system acts locally on the endometrium and cervical mucus. It binds to progesterone receptors, suppressing ovulation, thickening cervical mucus to impede sperm penetration, and inducing endometrial atrophy, which together prevent implantation of a fertilized egg. The device delivers approximately 20 µg of levonorgestrel per day, maintaining therapeutic levels directly within the uterine cavity while minimizing systemic exposure.

Levonorgestrel IUS may be associated with a range of adverse events, which are categorized by frequency and severity.

Common Side Effects

• Irregular bleeding or spotting
• Amenorrhea (absence of periods)
• Headache
• Breast tenderness
• Acne or oily skin
• Mood changes

Serious or Rare Side Effects

• Pelvic inflammatory disease
• Uterine perforation during insertion
• Expulsion of the device
• Ectopic pregnancy if contraception fails
• Ovarian cyst formation
• Severe allergic reaction (anaphylaxis)

Before insertion and during use, several precautions should be observed to ensure safety and effectiveness.

• Pregnancy testing: confirm non‑pregnant status prior to insertion.
• Regular follow‑up: schedule post‑insertion visits to verify correct device position.
• Contraindications: avoid in women with active pelvic infection, known uterine anomalies, or unexplained vaginal bleeding.
• Medication interactions: consider reduced efficacy when used with enzyme‑inducing drugs such as certain anticonvulsants.
• Smoking: advise cessation in women over 35 who smoke, due to increased cardiovascular risk.
• Store at ambient temperature: keep in original packaging, protect from moisture and direct sunlight.

Levonorgestrel released from Mirena can interact with other medicines, affecting its contraceptive reliability.

Major Interactions (Avoid)

• Enzyme‑inducing anticonvulsants (e.g., carbamazepine, phenytoin): may lower levonorgestrel effectiveness.
• Rifampin and other strong enzyme‑inducing antibiotics: may reduce contraceptive reliability.

Moderate Interactions (Monitor Closely)

• Antifungal azoles (e.g., ketoconazole): possible modest reduction in hormone activity.
• Protease inhibitor antiretrovirals: may alter levonorgestrel levels.
• St. John’s wort (hypericum perforatum): may decrease contraceptive efficacy.