Mirena (Levonorgestrel)

• Mirena, a levonorgestrel‑releasing intrauterine system, is used within the hormonal contraceptive pathway for reproductive health management.
• Contraception: provides up to five years of highly effective reversible birth control.
• Heavy menstrual bleeding: reduces menstrual blood loss and improves anemia associated with menorrhagia.
• Endometrial protection: induces endometrial atrophy, decreasing the risk of hyperplasia in women using estrogen therapy.
• Endometriosis‑related pain: may alleviate dysmenorrhea by suppressing ovulation and thinning the endometrium.

• Levonorgestrel released from the intrauterine system binds to progesterone receptors in the endometrium, cervical mucus, and the hypothalamic‑pituitary axis. This binding suppresses the mid‑cycle luteinizing hormone surge, preventing ovulation, while simultaneously thickening cervical mucus to impede sperm penetration and inducing endometrial atrophy, which reduces menstrual bleeding. The localized delivery yields systemic levonorgestrel levels far below oral contraceptive concentrations, minimizing systemic exposure.

Levonorgestrel IUS may be associated with a range of adverse reactions, ranging from mild to serious.

Common Side Effects

• Irregular bleeding: spotting or breakthrough bleeding during the first 3‑6 months as the endometrium adapts.
• Amenorrhea: absence of menstrual periods after the initial adjustment period.
• Pelvic pain: mild cramping or discomfort that usually resolves within weeks.
• Headache: occasional tension‑type headache, often transient.

Serious or Rare Side Effects

• Uterine perforation: rare injury occurring during insertion that may require surgical repair.
• Expulsion: device may be expelled spontaneously, necessitating re‑evaluation.
• Infection: pelvic inflammatory disease or endometritis can develop if aseptic technique is compromised.
• Hormone‑related thromboembolism: very rare clotting events that require immediate medical attention.

• Before Mirena insertion, clinicians should consider several safety measures.
• Screen for pregnancy: ensure the patient is not pregnant before insertion.
• Assess uterine anomalies: avoid use in abnormal uterine cavity or active infection.
• Monitor for expulsion: advise the patient to check strings regularly and report changes.
• Consider hormonal contraindications: avoid in women with known thrombophilia or hormone‑sensitive cancers.
• Inform about return of fertility: fertility resumes promptly after device removal.
• Store at room temperature: keep device in original packaging, protect from moisture and extreme temperatures.

Levonorgestrel released from an intrauterine system can interact with other medicines that affect hormone metabolism.

Major Interactions (Avoid)

• Enzyme inducers: strong CYP3A4 inducers (e.g., rifampicin) may reduce levonorgestrel efficacy.
• Antifungal agents: concurrent use of ketoconazole can increase systemic levonorgestrel levels, potentially raising side‑effect risk.

Moderate Interactions (Monitor Closely)

• Antiepileptics: carbamazepine or phenytoin may modestly lower levonorgestrel concentrations.
• Antibiotics: broad‑spectrum antibiotics such as tetracycline may have minimal effect, but monitoring is advised.
• Herbal supplements: St. John’s wort may decrease hormone levels, possibly reducing contraceptive effectiveness.