Mirena (Levonorgestrel)

• Levonorgestrel delivered by Mirena acts on the reproductive system to provide hormonal contraception and manage menstrual disorders.
• Contraception: offers highly effective reversible birth control for up to five years.
• Heavy menstrual bleeding: reduces menstrual blood loss and can improve anemia.
• Hormone replacement therapy adjunct: supplies progestogenic support when combined with estrogen in menopausal therapy.
• Endometrial protection in estrogen therapy: prevents estrogen‑induced endometrial hyperplasia.
• Management of abnormal uterine bleeding: stabilizes bleeding patterns in women with non‑structural causes.

• Mirena releases levonorgestrel directly into the uterine cavity at a low, steady rate. Levonorgestrel binds to progesterone receptors in the endometrium, causing decidualization and atrophy, which thins the lining and reduces menstrual flow. It also thickens cervical mucus, creating a barrier to sperm, and may suppress the hypothalamic‑pituitary‑ovarian axis, inhibiting ovulation in some users.

Levonorgestrel delivered via an intrauterine system can be associated with a range of local and systemic adverse reactions.

Common Side Effects

• Irregular bleeding or spotting: unpredictable bleeding patterns, especially in the first months.
• Amenorrhea: absence of menstrual periods after initial adjustment.
• Pelvic pain or cramping: mild to moderate discomfort.
• Headache: tension‑type or migraine‑like headaches.

Serious or Rare Side Effects

• Uterine perforation: rare injury to the uterine wall during insertion.
• Pelvic inflammatory disease: infection that can affect fertility.
• Ectopic pregnancy: pregnancy occurring outside the uterus if contraception fails.

When prescribing Mirena, clinicians should consider several safety and handling precautions.

• Patient selection: confirm the user is a non‑pregnant woman seeking contraception or bleeding management.
• Contraindications: avoid in women with active pelvic infection, unexplained vaginal bleeding, or known hypersensitivity to levonorgestrel.
• Screening: assess for uterine anomalies or fibroids that may impede insertion.
• Follow‑up: schedule a check‑up 4–6 weeks after insertion to confirm placement and address side effects.
• Removal: ensure timely removal or replacement at five years to maintain efficacy.
• Store at ambient temperature: keep the device in its original packaging, protect from moisture and direct sunlight.

Levonorgestrel released from Mirena may interact with other medications that affect hormonal balance or hepatic metabolism.

Major Interactions (Avoid)

• Antiepileptic enzyme inducers (e.g., carbamazepine, phenytoin, rifampicin): may reduce levonorgestrel levels and decrease contraceptive effectiveness.
• Antiretroviral protease inhibitors (e.g., ritonavir): can alter hormone metabolism, potentially lowering efficacy.
• Antifungal azoles (e.g., ketoconazole): may increase levonorgestrel concentrations, raising risk of side effects.

Moderate Interactions (Monitor Closely)

• Hormonal therapies (e.g., estrogen‑containing contraceptives): may require dosage adjustment if switching.
• St. John’s Wort: may modestly reduce hormone levels.
• Certain antibiotics (e.g., griseofulvin): limited effect but monitoring advised.