CYCLAFEM 0.5/35
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CYCLAFEM 0.5/35 (CYCLAFEM 0.5/35).
Combination oral contraceptive containing norethindrone (progestin) and ethinyl estradiol (estrogen). Inhibits gonadotropin release, suppressing ovulation. Increases cervical mucus viscosity and alters endometrium, reducing sperm penetration and implantation.
| Metabolism | Norethindrone undergoes hepatic metabolism via reduction and hydroxylation followed by glucuronidation; ethinyl estradiol is metabolized primarily by CYP3A4 and undergoes first-pass metabolism with sulfation and glucuronidation in the gut wall and liver. |
| Excretion | Renal excretion accounts for approximately 50-60% of the dose (as metabolites), with 30-40% excreted in feces via biliary elimination. Unchanged drug is minimal in urine. |
| Half-life | Terminal elimination half-life of norethindrone is 5-14 hours (mean 7.6 hours); ethinyl estradiol half-life is 7-20 hours (mean ~13 hours). Steady-state is achieved within 5-7 days. |
| Protein binding | Norethindrone: ~97% bound to albumin and SHBG. Ethinyl estradiol: ~98% bound to albumin. |
| Volume of Distribution | Norethindrone: Vd ~4 L/kg (total body water and tissue distribution). Ethinyl estradiol: Vd ~2.5 L/kg. |
| Bioavailability | Oral bioavailability: norethindrone ~64% (due to first-pass metabolism); ethinyl estradiol ~45% (range 38-55%). |
| Onset of Action | Oral: 7 days of consecutive dosing required for contraceptive effect; immediate on first day of menstrual cycle. |
| Duration of Action | Duration of contraceptive effect is 24 hours with daily dosing; after discontinuation, ovulation may resume within 2-4 weeks. |
One tablet (0.5 mg norethindrone/35 mcg ethinyl estradiol) orally once daily for 21 days, followed by 7 placebo days (or no tablets) per cycle.
| Dosage form | TABLET |
| Renal impairment | No specific dosage adjustment required for mild to moderate renal impairment. Contraindicated in severe renal impairment or acute renal failure due to potential adverse effects on renal function and hormonal balance. |
| Liver impairment | Contraindicated in Child-Pugh class B and C (moderate to severe hepatic impairment). For mild hepatic impairment (Child-Pugh class A), use with caution; no specific dose adjustment but monitor liver function tests. |
| Pediatric use | Not indicated for use before menarche. Post-menarche: same as adult dosing (one tablet daily per cycle) following standard contraceptive guidelines for adolescents. |
| Geriatric use | Not indicated for use in postmenopausal women due to lack of contraceptive need and increased risk of cardiovascular events and thromboembolism with estrogen-containing contraceptives. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CYCLAFEM 0.5/35 (CYCLAFEM 0.5/35).
| Breastfeeding | Contraindicated in breastfeeding. Estrogen and progestin are excreted in breast milk; M/P ratio unknown. May reduce milk production and alter milk composition. Theoretical risk of adverse effects in nursing infant. Alternative contraception recommended. |
| Teratogenic Risk | FIRST TRIMESTER: Increased risk of neural tube defects, cardiovascular malformations, and orofacial clefts with inadvertent exposure; absolute risk estimated at 3-4% above baseline. SECOND TRIMESTER: No direct teratogenic risk, but continue to avoid use due to hormonal effects. THIRD TRIMESTER: Potential for adverse fetal outcomes including respiratory distress, neonatal jaundice, and hypoglycemia; use contraindicated throughout pregnancy. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular events from combination oral contraceptives. Risk increases with age and with heavy smoking (≥15 cigarettes/day). Women over 35 who smoke should not use this product.
| Serious Effects |
["Thrombophlebitis or thromboembolic disorders (current or history)","Cerebrovascular or coronary artery disease","Known or suspected breast carcinoma","Endometrial carcinoma or other estrogen-sensitive neoplasia","Undiagnosed abnormal genital bleeding","Cholestatic jaundice of pregnancy or jaundice with prior pill use","Hepatic adenoma or carcinoma","Known or suspected pregnancy","Hypersensitivity to any component","Age >35 and smoking ≥15 cigarettes/day"]
| Precautions | ["Increased risk of thromboembolic disorders (e.g., stroke, MI, DVT, PE)","Increased risk of hepatic neoplasia (benign and malignant)","Elevated blood pressure","Gallbladder disease","Carbohydrate and lipid metabolism effects","Ocular changes (retinal thrombosis)","Depression","Headache/migraine","Hereditary angioedema exacerbation","Chloasma","Hepatic impairment","Pregnancy discontinuation","Lactation use"] |
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| Fetal Monitoring | Prior to initiation: Rule out pregnancy via sensitive hCG test. During use: Regular assessment for pregnancy symptoms; if pregnancy suspected, immediate discontinuation and confirmatory testing. Monitor for signs of pregnancy complications if inadvertent exposure occurs. |
| Fertility Effects | Reversible suppression of ovulation during use. Return to baseline fertility typically within 1-3 cycles after discontinuation. No evidence of long-term negative impact on fertility. Use may mask underlying fertility issues. |