Mirena (Levonorgestrel)

Mirena (levonorgestrel intrauterine system) is used in the reproductive health pathway for hormonal contraception and menstrual management.

• Contraception: provides >99% effective birth control for up to five years after insertion.
• Heavy menstrual bleeding: reduces menstrual blood loss and improves anemia associated with excessive bleeding.
• Endometrial protection: thins the endometrium, decreasing the risk of hyperplasia in women using the device.

• Levonorgestrel released from the intrauterine system acts locally on the uterine lining and cervical mucus. It binds to progesterone receptors, causing the endometrium to become thin and atrophic, while simultaneously thickening cervical mucus to impede sperm penetration. The hormone also exerts a partial suppressive effect on the hypothalamic‑pituitary‑ovarian axis, reducing the frequency of ovulation, which together produce a highly effective contraceptive effect.

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

Common Side Effects

• Irregular vaginal bleeding or spotting
• Amenorrhea (absence of periods)
• Pelvic or abdominal pain
• Breast tenderness
• Hormonal acne
• Ovarian cyst formation
• Headache
• Mood changes

Serious or Rare Side Effects

• Uterine perforation during insertion
• IUS expulsion or displacement
• Pelvic inflammatory infection
• Ectopic pregnancy if contraception fails
• Thromboembolic events (rare)
• Severe allergic reaction
• Severe abdominal pain or fever

Prior to insertion and during use, certain precautions should be observed to ensure safety and optimal performance of the levonorgestrel intrauterine system.

• Pregnancy screening: confirm the patient is not pregnant before insertion.
• Medical history review: assess for uterine anomalies, active pelvic infection, or malignancy.
• Contraindications check: avoid use in women with known or suspected breast or genital tract cancer.
• Follow‑up care: schedule a pelvic examination 4–6 weeks after insertion to verify placement.
• Drug interactions: be aware that enzyme‑inducing medications may reduce contraceptive efficacy.
• Store at ambient temperature: keep the device in its original packaging, protect from moisture and direct sunlight.

Levonorgestrel released from the IUS can interact with other medicines that affect its metabolism or hormonal activity.

Major Interactions (Avoid)

• Enzyme‑inducing antiepileptics (e.g., carbamazepine, phenytoin, phenobarbital): may markedly lower levonorgestrel levels.
• Rifampin and rifabutin: strong inducers that can reduce contraceptive effectiveness.
• Griseofulvin: may decrease hormone concentrations leading to reduced efficacy.

Moderate Interactions (Monitor Closely)

• Azole antifungals (e.g., ketoconazole, itraconazole): can increase levonorgestrel exposure and risk of side effects.
• Protease inhibitor antiretrovirals (e.g., ritonavir): may alter hormone metabolism, requiring clinical monitoring.
• St. John’s wort: herbal inducer that could lower contraceptive reliability.