Misstala (Ulipristal Acetate)

Ulipristal acetate works within the reproductive hormone pathway to provide both emergency contraceptive and fibroid‑related benefits.

• Emergency contraception: prevents or delays ovulation to reduce the risk of pregnancy after unprotected sex.
• Uterine fibroids: reduces fibroid size and associated heavy menstrual bleeding in women with symptomatic leiomyomas.

• Ulipristal acetate binds competitively to progesterone receptors, acting as an antagonist that blocks progesterone‑mediated signaling. This inhibition prevents the luteinizing hormone surge required for ovulation, thereby delaying or stopping follicular rupture. In uterine fibroids, the antagonism reduces cellular proliferation and induces apoptosis, leading to decreased fibroid volume and bleeding.

Ulipristal acetate may cause a range of adverse reactions, most of which are mild and transient.

Common Side Effects

• Nausea: mild to moderate stomach upset.
• Headache: intermittent tension‑type headaches.
• Abdominal pain: cramping or discomfort in the lower abdomen.
• Fatigue: feeling unusually tired.
• Dizziness: light‑headed sensation.
• Menstrual changes: spotting or altered cycle timing.

Serious or Rare Side Effects

• Hepatic injury: signs of liver dysfunction such as jaundice.
• Severe allergic reaction: rash, swelling, or anaphylaxis.
• Thromboembolic events: unusual clot formation.
• Endometrial changes: atypical uterine bleeding.
• Pregnancy complications: if taken during early pregnancy.
• Vision disturbances: blurred or double vision.

Before using Misstala, consider the following safety measures.

• Pregnancy contraindication: avoid use if pregnancy is confirmed or suspected.
• Liver disease: use with caution in patients with hepatic impairment.
• Drug interactions: avoid concomitant strong CYP3A4 inducers that may reduce efficacy.
• Timing limitation: do not exceed the recommended window for emergency contraception.
• Hypersensitivity: discontinue if signs of allergic reaction appear.
• Store at ambient temperature: keep in the original packaging, protect from moisture and direct sunlight.

Ulipristal acetate can interact with other medicines, affecting its effectiveness or safety.

Major Interactions (Avoid)

• Strong CYP3A4 inducers (e.g., rifampicin, phenytoin, carbamazepine): may markedly reduce drug levels.
• Other selective progesterone receptor modulators: may increase risk of adverse hormonal effects.

Moderate Interactions (Monitor Closely)

• Hormonal contraceptives: may require additional contraceptive measures.
• Antifungal agents (e.g., ketoconazole): can increase plasma concentrations.
• St. John’s wort: may lower effectiveness.
• Anticonvulsants (e.g., phenobarbital): may modestly reduce drug exposure.