Mirena (Levonorgestrel)

• Mirena (levonorgestrel intrauterine system) is used in the reproductive health field to provide hormonal contraception and manage menstrual disorders.
• Contraception: provides up to five years of highly effective, reversible birth control by preventing ovulation and creating a cervical mucus barrier.
• Heavy menstrual bleeding: reduces menstrual blood loss by thinning the endometrial lining, leading to lighter periods and improvement of anemia associated with excessive bleeding.
• Endometrial protection during estrogen therapy: maintains a stable endometrial environment, preventing estrogen‑induced hyperplasia in women using combined hormone replacement therapy.

• Levonorgestrel released from the intrauterine system acts locally on the uterine tissue. It suppresses the hypothalamic‑pituitary‑ovarian axis, inhibiting the mid‑cycle LH surge and thereby preventing ovulation. In addition, it thickens cervical mucus, reducing sperm penetration, and induces endometrial atrophy, creating an environment unsuitable for implantation. These combined actions result in effective contraception and also modulate the endometrial response, which accounts for the reduction in menstrual blood loss.

Levonorgestrel delivered via the Mirena intrauterine system may be associated with a range of adverse reactions.

Common Side Effects

• Irregular bleeding or spotting: occasional light bleeding between periods, usually resolves over time.
• Amenorrhea (absence of periods): menstrual cycles may stop during use, often returning after removal.
• Headache: mild to moderate tension‑type headaches, may improve with analgesics.
• Breast tenderness: temporary soreness or swelling of the breasts, typically diminishes after initial months.
• Acne: emergence or worsening of facial pimples, generally mild.
• Mood changes: irritability or mild depressive symptoms, should be monitored.

Serious or Rare Side Effects

• Pelvic inflammatory disease: infection of the reproductive organs requiring medical attention.
• Uterine perforation: rare injury to the uterine wall during insertion.
• Ectopic pregnancy: pregnancy occurring outside the uterus, most commonly in the fallopian tube.

Before using Mirena, healthcare providers should consider several precautionary measures to ensure safety and effectiveness.

• Patient selection: confirm no active pelvic infection or uterine anomalies.
• Pregnancy status: contraindicated in known or suspected pregnancy; ensure negative test before insertion.
• Breastfeeding: evaluate risks and benefits, as levonorgestrel is excreted in milk.
• Smoking: advise against use in women over 35 who smoke heavily due to cardiovascular risk.
• Follow‑up: schedule pelvic exam 4‑6 weeks after insertion to verify placement.
• Store at room temperature: keep the device in original packaging, protect from moisture and extreme heat.

Levonorgestrel released from Mirena can interact with other medications, affecting its efficacy or safety.

Major Interactions (Avoid)

• Antiepileptic enzyme inducers (e.g., carbamazepine, phenytoin, rifampicin): may reduce levonorgestrel levels and compromise contraceptive effectiveness.
• Antitubercular agents (rifampin): similar enzyme induction leading to decreased hormone concentrations.

Moderate Interactions (Monitor Closely)

• Antifungal azoles (ketoconazole, itraconazole): can increase levonorgestrel exposure, potentially heightening side effects.
• Antiretroviral drugs (efavirenz, nevirapine): may modestly lower hormone levels, requiring additional contraceptive measures.
• St. John’s wort: herbal inducer that may lower efficacy; advise patient to avoid or use backup contraception.