Mirena (Levonorgestrel)

Levonorgestrel, a synthetic progestogen, is employed within hormonal contraceptive and menstrual‑management pathways.

• Contraception (long‑acting reversible contraceptive): Provides highly effective pregnancy prevention for up to five years.
• Heavy menstrual bleeding: Reduces menstrual blood loss and can improve anemia associated with excessive bleeding.

• Levonorgestrel released from the intrauterine system acts locally on the endometrium and cervical mucus. It thickens cervical mucus, impairing sperm motility and function, induces endometrial atrophy, and may suppress ovulation. The combined actions create an environment unfavorable for fertilisation and implantation, thereby preventing pregnancy while also decreasing endometrial growth that contributes to heavy menstrual bleeding. The low systemic exposure minimizes hormonal side effects compared with oral progestogens.

Levonorgestrel IUS may be associated with a range of adverse reactions, varying in frequency and severity.

Common Side Effects

• Irregular vaginal bleeding or spotting.
• Amenorrhea (absence of periods) after several months.
• Pelvic or abdominal cramping.
• Hormonal changes such as breast tenderness or mood swings.

Serious or Rare Side Effects

• Uterine perforation during insertion.
• Device expulsion or displacement.
• Pelvic inflammatory disease or severe infection.

Prior to insertion and during use, several precautions should be observed to ensure safety and effectiveness.

• Pregnancy testing: Confirm the patient is not pregnant before insertion.
• Uterine evaluation: Screen for fibroids, polyps, or congenital anomalies that may impede placement.
• Active infection: Defer insertion in the presence of pelvic inflammatory disease or genital infection.
• Expulsion risk: Counsel patients on signs of device displacement and schedule follow‑up checks.
• Hormonal contraindications: Avoid use in women with known thrombophilia or hormone‑sensitive cancers.
• Store at room temperature: Keep the device in its original packaging, protect from moisture and direct sunlight.

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

Major Interactions (Avoid)

• Enzyme‑inducing antiepileptics (e.g., carbamazepine, phenytoin): May lower levonorgestrel levels and reduce efficacy.
• Rifampicin or rifabutin: Strong hepatic inducers that can diminish contraceptive protection.
• Antiretroviral efavirenz: Can decrease hormonal concentrations, increasing pregnancy risk.

Moderate Interactions (Monitor Closely)

• St John’s wort: Herbal inducer that may modestly reduce levonorgestrel exposure.
• Antifungal azoles (e.g., ketoconazole): May increase levonorgestrel levels, potentially heightening side‑effect risk.
• Estrogen‑containing hormonal therapies: Combined use can raise the risk of thromboembolic events.