Mirena (Levonorgestrel)

Mirena, a levonorgestrel‑releasing intrauterine system, is used in gynecologic indications that require local hormonal modulation.

• Contraception: provides reversible birth control for up to five years with a low failure rate.
• Heavy menstrual bleeding: reduces menstrual blood loss and improves anemia associated with menorrhagia.
• Non‑atypical endometrial hyperplasia: helps control endometrial proliferation as an adjunct therapy.

• The intrauterine system releases levonorgestrel locally, which binds to progesterone receptors in the endometrium, suppressing its proliferation, thickening cervical mucus to impede sperm penetration, and may partially inhibit ovulation. This localized hormonal effect provides contraceptive efficacy while minimizing systemic exposure.

Common Side Effects

• Irregular bleeding or spotting: unpredictable bleeding patterns during the first months.
• Amenorrhea: absence of menstrual periods after prolonged use.
• Pelvic or cramping pain: mild discomfort related to device presence.
• Hormonal acne: skin changes due to progestogenic activity.

Serious or Rare Side Effects

• Uterine perforation: rare injury to the uterine wall during insertion.
• Device expulsion: accidental loss of the IUS requiring re‑evaluation.
• Pelvic inflammatory disease: infection that may develop after insertion.
• Ectopic pregnancy: occurs if pregnancy happens despite device use.
• Ovarian cyst formation: cysts that may require monitoring.

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

• Pregnancy testing: confirm a negative pregnancy test prior to insertion.
• Uterine evaluation: assess for fibroids, congenital anomalies, or scarring that could affect placement.
• Active infection: treat any pelvic infection before device placement.
• Bleeding disorders: evaluate clotting status and discuss risks with the patient.
• Breastfeeding: consider benefits and risks, especially in the immediate postpartum period.
• Store at room temperature: keep in original packaging, protect from moisture and direct sunlight.

Levonorgestrel released from Mirena may interact with other medicines that affect hormone metabolism or uterine environment.

Major Interactions (Avoid)

• Enzyme‑inducing antiepileptics (e.g., carbamazepine, phenytoin): may reduce levonorgestrel efficacy.
• Rifampin and other strong antibiotic inducers: may lower hormone levels and increase risk of unintended pregnancy.

Moderate Interactions (Monitor Closely)

• Combined hormonal contraceptives: may alter bleeding patterns when used concurrently.
• Antifungal azoles (e.g., ketoconazole): can increase levonorgestrel concentrations.
• St. John’s wort: herbal inducer that may decrease hormonal effectiveness.