Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PREGNYL vs AFIRMELLE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Human chorionic gonadotropin (h CG) acts as a luteinizing hormone (LH) agonist, binding to LH receptors in the gonads, stimulating testosterone production in males and ovulation in females.
Combination oral contraceptive containing ethinyl estradiol and levonorgestrel. Inhibits ovulation by suppressing gonadotropin release (FSH and LH). Also increases cervical mucus viscosity and alters endometrial receptivity.
FDA: Treatment of prepubertal cryptorchidism,FDA: Induction of ovulation and pregnancy in anovulatory infertile women,Off-label: Hypogonadotropic hypogonadism in males,Off-label: Assisted reproductive technology (ART) protocols
Prevention of pregnancy (FDA-approved)
Intramuscular injection: 5,000-10,000 IU once weekly for 4-9 weeks for ovulation induction; 1,000-2,000 IU three times weekly for spermatogenesis.
One tablet (0.1 mg levonorgestrel, 0.02 mg ethinyl estradiol) orally once daily for 21 days, followed by 7 days of placebo.
Terminal elimination half-life: 23–24 hours; clinically, supports daily or every-other-day dosing; peak effect may lag due to prolonged absorption
Terminal elimination half-life: 12–15 hours. Steady-state achieved within 5 days with Q12H dosing.
Primarily renal metabolism and excretion; limited hepatic metabolism.
Ethinyl estradiol undergoes first-pass metabolism in gut and liver via CYP3A4, with conjugation to sulfate and glucuronide. Levonorgestrel is metabolized primarily by CYP3A4 to reduced and hydroxylated metabolites, then conjugated.
Renal: 10-20% as unchanged drug; hepatic metabolism to inactive metabolites; fecal excretion negligible (<5%)
Renal: 50% as unchanged drug and metabolites; fecal: 40% as metabolites; biliary: ~10% as glucuronide conjugates.
~80% bound primarily to albumin; minor binding to sex hormone-binding globulin (SHBG)
~99% bound to serum albumin and sex hormone-binding globulin.
0.5–0.7 L/kg; moderately distributed into extracellular fluid; penetrates gonadal tissues
2.8 L/kg (apparent Vd), indicating extensive tissue distribution.
Intramuscular: ~100%; Subcutaneous: comparable (~95-100%); Oral: <5% (not used)
Oral: ~70% due to first-pass metabolism.
No specific guidelines; use with caution in severe renal impairment (Cr Cl <30 m L/min) due to limited data.
No dose adjustment required for mild to moderate renal impairment. Not recommended for use in end-stage renal disease.
No specific guidelines for Child-Pugh; use with caution in severe hepatic impairment.
Contraindicated in acute hepatic disease or severe (Child-Pugh C) hepatic impairment. Use with caution in mild to moderate hepatic impairment; monitor liver function.
Not indicated for prepubertal children; for delayed puberty in males: 1,000-2,000 IU intramuscularly 2-3 times weekly for 3-6 months.
Not indicated for use before menarche. Post-menarche: same as adult dosing (one tablet daily) based on adult clinical trials.
No specific recommendations; use lowest effective dose due to potential increased sensitivity and comorbidities.
Not indicated for use in postmenopausal women; no specific dose adjustment required in healthy elderly, but limited data available.
No FDA black box warning.
Cigarette smoking increases risk of serious cardiovascular events from combination oral contraceptive use. Risk increases with age (especially in women over 35) and with heavy smoking (15+ cigarettes/day). Women who use combination hormonal contraceptives should be strongly advised not to smoke.
Ovarian hyperstimulation syndrome (OHSS) in women,Arterial thromboembolism,Precocious puberty in males,Fluid retention,Ovarian enlargement or cyst rupture
Thrombotic disorders (venous thromboembolism, stroke, myocardial infarction),Cigarette smoking (increases cardiovascular risk),Hypertension (especially in women with renal disease or migraines),Gallbladder disease,Hepatic neoplasia (benign and malignant),Carbohydrate and lipid metabolism effects,Ocular lesions (retinal thrombosis),Depressed mood or depression,Uterine bleeding irregularities,Reduced efficacy with hepatic enzyme inducers
Hypersensitivity to h CG or any component,Premature epiphyseal closure in males,Androgen-dependent neoplasia (e.g., prostate cancer),Undiagnosed uterine bleeding,Ovarian cyst or enlargement due to polycystic ovarian syndrome (PCOS),Active thromboembolic disorders
Thrombophlebitis or thromboembolic disorders (current or history),Cerebrovascular or coronary artery disease (current or history),Known or suspected breast cancer, endometrial cancer, or other estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Cholestatic jaundice of pregnancy or jaundice with prior oral contraceptive use,Hepatic adenoma or carcinoma (current or history),Known or suspected pregnancy,Hypersensitivity to any component of the product,Heavy smoking (≥15 cigarettes/day) in women over 35
No known clinically significant food interactions. Maintain usual diet unless advised otherwise by physician.
Grapefruit juice may increase ethinyl estradiol levels; avoid large quantities. No significant food restrictions. Administer with food if GI upset occurs.
Pregny (h CG) is not indicated for use during pregnancy. h CG is used to induce ovulation and is not continued after conception. In animal studies, high doses have shown fetal abnormalities, but human data are insufficient. First trimester: No direct fetal risk from therapeutic use as it is discontinued before implantation. Second/Third trimester: Not used. Overall, classified as FDA Pregnancy Category X for ovulation induction (contraindicated in pregnancy) but no teratogenic risk if discontinued before conception.
Pregnancy category X. Contraindicated in pregnancy due to risk of fetal harm. First trimester: exposure associated with congenital anomalies (e.g., cardiovascular, neural tube defects). Second and third trimesters: increased risk of fetal growth restriction, preterm birth, and neonatal respiratory distress. Postnatal: possible long-term developmental effects.
Human chorionic gonadotropin (h CG) is normally present in breast milk in low concentrations. Exogenous h CG is likely excreted into breast milk, but the M/P ratio is not established. Due to lack of data and potential for adverse effects in the infant (e.g., hormonal disruption), breastfeeding is not recommended during therapy. The manufacturer advises discontinuing breastfeeding or avoiding the drug.
Contraindicated during breastfeeding. Small amounts of ethinyl estradiol and norethindrone are excreted in breast milk; M/P ratio not well defined. Potential for adverse effects on infant (e.g., jaundice, breast enlargement). May reduce milk production and quality.
Pregny is contraindicated in pregnancy. No dose adjustment is applicable as it is discontinued prior to conception. There are no pharmacokinetic data for pregnancy, but the drug is not used during gestation.
Contraindicated in pregnancy; no dose adjustment recommended. If exposure occurs, immediate discontinuation is required. No pharmacokinetic data support safe use; avoid use entirely.
Pregnyl (h CG) is used to trigger final follicular maturation and ovulation in assisted reproduction. Monitor for ovarian hyperstimulation syndrome (OHSS); consider withholding h CG if estradiol >4000 pg/m L or >20 follicles per ovary. Administer exactly 36 hours before oocyte retrieval. Intramuscular injection into gluteal muscle; rotate sites if repeated doses.
Afirmelle (levonorgestrel/ethinyl estradiol) is a combined oral contraceptive. Counsel patients to take at the same time daily to maintain consistent hormone levels. Use back-up contraception if a dose is missed. Monitor for signs of thromboembolism, especially in smokers over 35. Advise that certain antibiotics (e.g., rifampin) and anticonvulsants (e.g., phenytoin) may reduce efficacy. Consider progestin-only pill if contraindications to estrogen exist.
Use Pregnyl exactly as prescribed to trigger ovulation; timing is critical for egg retrieval.,Report severe pelvic pain, bloating, nausea, or rapid weight gain (possible OHSS) immediately.,Avoid pregnancy tests during treatment as h CG may cause false positive.,May cause injection site pain or swelling; apply warm compress if needed.,Do not discontinue without consulting your fertility specialist.
Take one pill at the same time every day, even if you don't have sex.,If you miss a pill, follow the instructions in the package insert or ask your healthcare provider.,Use a backup method (like condoms) if you start late or miss pills.,This medication does not protect against HIV or other sexually transmitted infections.,Common side effects include nausea, breast tenderness, and breakthrough bleeding.,Seek medical help if you have symptoms of a blood clot: sudden chest pain, leg swelling, or shortness of breath.,Smoking while on this pill increases your risk of serious cardiovascular events.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about PREGNYL vs AFIRMELLE, answered by our medical review team.
PREGNYL is a Gonadotropin Hormone that works by Human chorionic gonadotropin (h CG) acts as a luteinizing hormone (LH) agonist, binding to LH receptors in the gonads, stimulating testosterone production in males and ovulation in females.. AFIRMELLE is a Combined Oral Contraceptive that works by Combination oral contraceptive containing ethinyl estradiol and levonorgestrel. Inhibits ovulation by suppressing gonadotropin release (FSH and LH). Also increases cervical mucus viscosity and alters endometrial receptivity.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PREGNYL and AFIRMELLE depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of PREGNYL is: Intramuscular injection: 5,000-10,000 IU once weekly for 4-9 weeks for ovulation induction; 1,000-2,000 IU three times weekly for spermatogenesis.. The standard adult dose of AFIRMELLE is: One tablet (0.1 mg levonorgestrel, 0.02 mg ethinyl estradiol) orally once daily for 21 days, followed by 7 days of placebo.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between PREGNYL and AFIRMELLE in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. PREGNYL is classified as Category C. Pregny (hCG) is not indicated for use during pregnancy. hCG is used to induce ovulation and is not continued after conception. In animal studies, high doses have shown fetal abnorm. AFIRMELLE is classified as Category C. Pregnancy category X. Contraindicated in pregnancy due to risk of fetal harm. First trimester: exposure associated with congenital anomalies (e.g., cardiovascular, neural tube defe. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.