Cerazette prevents pregnancy through three primary mechanisms:

1. Ovulation Suppression: Desogestrel inhibits the release of luteinizing hormone (LH), preventing ovulation in 97% of cycles (Lippincott).
2. Cervical Mucus Alteration: Thickens cervical mucus, creating a barrier to sperm penetration.
3. Endometrial Changes: Thins the endometrial lining, reducing the likelihood of implantation (Lange).

Desogestrel, a third-generation progestin, has high selectivity for progesterone receptors with minimal androgenic, estrogenic, or glucocorticoid activity, making it well-tolerated.

1. Contraception: Primary indication, with >99% efficacy when used correctly (BNF).
2. Estrogen Contraindications: Suitable for women with contraindications to estrogen, such as a history of venous thromboembolism (VTE), hypertension, or migraine with aura.
3. Breastfeeding: Safe for use during lactation, as it does not affect milk supply (Lippincott).

• Standard Regimen: One tablet (75 µg desogestrel) daily at the same time each day, without a hormone-free interval (BNF).
• Initiation: Start on day 1 of menstruation for immediate protection. If started later, use backup contraception for 7 days.
• Missed Dose: If delayed >12 hours, take the missed pill immediately and use backup contraception for 7 days.

• Common: Irregular menstrual bleeding (e.g., spotting, amenorrhea), headache, breast tenderness, nausea, and mood changes.
• Serious:
  • Ectopic Pregnancy: Rare but possible due to altered tubal motility (Lange).
  • Ovarian Cysts: Benign functional cysts may occur due to suppressed ovulation.
  • Hepatic Effects: Rare hepatotoxicity or benign liver tumors (BNF).

• Absolute Contraindications: History of progesterone-dependent tumors, severe liver disease, or undiagnosed vaginal bleeding (BNF).
• Relative Precautions: History of depression, diabetes, or risk factors for ectopic pregnancy.
• Monitoring: Regular follow-up for menstrual irregularities and screening for hepatic dysfunction in long-term users.

• Reduced Efficacy: Enzyme-inducing drugs (e.g., rifampicin, carbamazepine, St. John’s Wort) accelerate metabolism of desogestrel, necessitating alternative contraception (BNF).
• Antibiotics: Limited evidence for interaction with broad-spectrum antibiotics (e.g., amoxicillin), but backup contraception is advised.
• Other Interactions: Avoid concurrent use with hepatotoxic drugs (e.g., acetaminophen overdose) or cyclosporine (desogestrel may increase plasma levels) (Lippincott).

• Active Ingredient: Desogestrel (75 µg).
• Brands: Marketed as Cerazette; generics may be labeled as desogestrel.