Mirena (Levonorgestrel)

Levonorgestrel delivered via Mirena acts on the hormonal regulation of the reproductive system.

• Contraception: provides highly effective long‑term birth control for up to five years.
• Heavy menstrual bleeding: reduces menstrual blood loss and improves anemia.
• Benign endometrial hyperplasia: helps manage non‑cancerous overgrowth of the endometrium.

• Levonorgestrel is released locally from the intrauterine system, where it binds to progesterone receptors in the endometrium, suppressing proliferation, thickening cervical mucus to impede sperm penetration, and partially inhibiting ovulation, thereby delivering contraceptive efficacy and reducing menstrual bleeding.

Common side effects are generally mild and related to the local hormonal action of the device.

Common Side Effects

• Altered bleeding patterns: spotting, irregular bleeding, or amenorrhea.
• Pelvic or cramping pain during and after insertion.
• Breast tenderness or enlargement.
• Mood changes or mild depression.
• Headache.
• Nausea.

Serious or Rare Side Effects

• Uterine perforation during insertion.
• Device expulsion or displacement.
• Pelvic inflammatory infection.
• Ovarian cyst formation.
• Allergic reaction to device components.
• Ectopic pregnancy if contraception fails.

Before insertion, clinicians should evaluate patient history and ensure appropriate conditions for safe use.

• Pregnancy status: confirm the patient is not pregnant before insertion.
• Uterine abnormalities: assess for fibroids, congenital anomalies, or scarring.
• Active pelvic infection: defer insertion until infection resolves.
• Bleeding changes: counsel patients about possible irregular bleeding or amenorrhea.
• Signs of perforation: monitor for severe abdominal pain or abnormal bleeding.
• Store at room temperature: keep in the original pack, protect from moisture.

Levonorgestrel released from Mirena may have its efficacy altered by concomitant medications that affect steroid metabolism.

Major Interactions (Avoid)

• Enzyme‑inducing anticonvulsants (e.g., carbamazepine, phenytoin) that lower levonorgestrel levels.
• Rifampin or other strong CYP3A inducers that may reduce contraceptive effectiveness.
• St. John’s wort, a herbal CYP3A inducer, potentially decreasing hormone exposure.

Moderate Interactions (Monitor Closely)

• Antiretroviral agents (e.g., efavirenz) that may modestly reduce hormone levels.
• Azole antifungals (e.g., ketoconazole) that could increase levonorgestrel concentrations.
• Combined hormonal contraceptives used concurrently; monitor for additive hormonal effects.