Mirena (Levonorgestrel)

Mirena (levonorgestrel) is a hormonal intrauterine device used in reproductive health.

• Contraception: provides highly effective, reversible birth control for up to five years.
• Heavy menstrual bleeding: reduces menstrual blood loss and may improve anemia associated with excessive bleeding.
• Dysmenorrhea: can alleviate painful periods that accompany heavy bleeding.
• Endometrial hyperplasia (benign): may be employed off‑label to manage non‑cancerous endometrial overgrowth.

• Levonorgestrel released from the intrauterine system acts locally on the endometrium and cervical mucus. It suppresses ovulation by inhibiting the luteinizing hormone surge, induces a thickened cervical mucus barrier that impedes sperm penetration, and creates a thin, atrophic endometrial lining that is unsuitable for implantation. These combined actions maintain a contraceptive environment within the uterus for the duration of device use.

Levonorgestrel IUS may be associated with a range of adverse reactions, which are categorized by frequency and severity, and should be monitored during use.

Common Side Effects

• Irregular bleeding or spotting
• Amenorrhea (absence of periods)
• Pelvic or uterine cramping
• Breast tenderness
• Ovarian cyst formation
• Headache

Serious or Rare Side Effects

• Uterine perforation
• Device expulsion
• Pelvic infection (including tubo‑ovarian abscess)
• Ectopic pregnancy
• Severe mood changes or depression
• Allergic reaction (rash, swelling, anaphylaxis)

Patients should report any unexpected symptoms promptly to their healthcare provider. Most side effects are mild and resolve over time, but serious events require immediate medical attention.

Before insertion and during use of Mirena, healthcare professionals should observe several precautionary measures to ensure safety and effectiveness.

• Confirm uterine position: perform a pelvic exam and ultrasound to verify correct placement.
• Exclude pregnancy: ensure the patient is not pregnant before insertion.
• Avoid in active infection: do not insert in the presence of pelvic inflammatory disease or genital infection.
• Counsel on bleeding pattern: inform patients that irregular bleeding or spotting is common initially.
• Review hormone‑sensitive conditions: assess history of breast cancer, liver disease, or thromboembolic disorders.
• Store at room temperature: keep the device in its original packaging, protect from moisture and direct sunlight.

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

Major Interactions (Avoid)

• CYP3A4 inducers (e.g., rifampin, carbamazepine, phenytoin): may reduce levonorgestrel efficacy.
• Antifungal azoles (e.g., ketoconazole, itraconazole): can increase systemic hormone levels, raising side‑effect risk.
• Protease inhibitors (e.g., ritonavir): may alter hormone concentrations and affect contraceptive reliability.

Moderate Interactions (Monitor Closely)

• St. John’s wort: may modestly decrease levonorgestrel exposure.
• Certain antibiotics (e.g., rifampin is major, others generally low risk): monitor for breakthrough bleeding.