Mirena (Levonorgestrel)

Mirena (levonorgestrel intrauterine system) is used in hormonal contraception and management of menstrual disorders.

• Contraception: provides long‑acting reversible birth control for women of reproductive age.
• Heavy menstrual bleeding: reduces menstrual blood loss and improves anemia associated with menorrhagia.
• Endometrial protection in hormone replacement therapy: thins the endometrium to prevent hyperplasia when estrogen is administered.

• Levonorgestrel is released locally from the intrauterine system, where it binds to progesterone receptors in the endometrium, causing stromal decidualization and suppressing glandular proliferation. The hormone also thickens cervical mucus, creating a barrier to sperm penetration, and in many users it inhibits ovulation by suppressing the hypothalamic‑pituitary‑ovarian axis.

Adverse reactions may occur with any intrauterine device. Monitoring and prompt medical attention are advised if symptoms develop.

Common Side Effects

• Irregular vaginal bleeding or spotting.
• Amenorrhea (absence of periods) after several months.
• Cramping or pelvic pain after insertion.
• Ovarian cyst formation.
• Headache or breast tenderness.
• Mood changes or acne.

Serious or Rare Side Effects

• Uterine perforation during insertion.
• Device expulsion or displacement.
• Pelvic inflammatory disease or infection.
• Ectopic pregnancy if contraception fails.
• Severe allergic reaction (anaphylaxis).
• Deep vein thrombosis or pulmonary embolism (very rare).

Before insertion, a thorough medical assessment is required to ensure suitability and minimize risks.

• Pregnancy screening: confirm the patient is not pregnant before placement.
• Contraindications: avoid in active pelvic infection, uterine anomalies, or known or suspected malignancy of the breast or reproductive organs.
• Uterine position: verify a normal uterine cavity size and orientation via ultrasound.
• Follow‑up: schedule a check‑up 4–6 weeks after insertion and annually thereafter.
• Avoid insertion during pregnancy: postpone until a negative pregnancy test is confirmed.
• Store at ambient temperature: keep in the original packaging, protect from moisture and direct sunlight.

Levonorgestrel released from an intrauterine system has limited systemic exposure, yet certain drugs may affect its efficacy.

Major Interactions (Avoid)

• Enzyme‑inducing anticonvulsants (e.g., carbamazepine, phenytoin): may lower levonorgestrel levels.
• Rifampin or other strong CYP3A4 inducers: may reduce contraceptive effectiveness.

Moderate Interactions (Monitor Closely)

• Antifungal agents (e.g., ketoconazole): could increase levonorgestrel concentrations.
• St. John's wort: may diminish hormonal activity.
• Combined hormonal contraceptives: concurrent use may increase overall hormonal exposure.
• Hormone replacement therapy: may require dose adjustment of systemic estrogen.