FACTREL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FACTREL (FACTREL).
Gonadotropin-releasing hormone (GnRH) agonist; stimulates pituitary release of LH and FSH initially, then suppresses gonadotropin secretion after chronic administration due to receptor downregulation.
| Metabolism | Rapidly hydrolyzed by peptidases in plasma and tissues; half-life approximately 10-40 minutes. |
| Excretion | Primarily renal (95% as unchanged drug and metabolites). Fecal excretion accounts for <5%. |
| Half-life | Terminal elimination half-life is approximately 30-45 minutes. Short half-life necessitates continuous or repeated administration for sustained therapeutic effect. |
| Protein binding | Approximately 40-50%, primarily to albumin. |
| Volume of Distribution | 0.6-1.0 L/kg, suggesting distribution into total body water. |
| Bioavailability | Subcutaneous: 70-80%; Intramuscular: 60-70%; Intranasal: 5-10%. |
| Onset of Action | Intravenous: within 1-2 minutes. Subcutaneous: 5-10 minutes. Intramuscular: 10-15 minutes. |
| Duration of Action | Single dose: 2-4 hours. Clinical effect duration is short; repeated dosing or continuous infusion is required for sustained gonadotropin suppression. |
| Molecular Weight | 1182.27 |
100 mcg subcutaneously or 100 mcg intravenously, single dose for pituitary stimulation testing.
| Dosage form | INJECTABLE |
| Renal impairment | No dosage adjustment required for renal impairment. GFR not clinically relevant for single-dose diagnostic use. |
| Liver impairment | No dosage adjustment required for hepatic impairment. Child-Pugh classification not applicable for single-dose diagnostic use. |
| Pediatric use | 2 mcg/kg subcutaneously or intravenously, single dose for pituitary stimulation testing in children. |
| Geriatric use | No specific dosage adjustment; use adult dosing as recommended. Consider general fragility and comorbidities. |
| 1st trimester | Gonadotropin-releasing hormone (GnRH) agonists like FACTREL are contraindicated during pregnancy. Use in first trimester may interfere with early embryonic development due to hormonal effects. |
| 2nd trimester | Contraindicated. Potential risk of fetal harm due to hormonal alterations. |
| 3rd trimester | Contraindicated. May affect fetal gonadal development and hormonal balance. |
Clinical note
Comprehensive clinical and safety monograph for FACTREL (FACTREL).
| Placental transfer | GnRH agonists are known to cross the placenta based on animal studies. Limited human data but transfer is expected due to low molecular weight and lipophilic nature. |
| Breastfeeding | Excretion into breast milk is unknown. Due to potential for hormonal effects in the infant, use during breastfeeding is not recommended unless clearly necessary and benefit outweighs risk. |
■ FDA Black Box Warning
No FDA boxed warning is present for Factrel.
| Serious Effects |
Hypersensitivity to gonadorelin or any component of the formulationPregnancyUndiagnosed abnormal vaginal bleedingKnown or suspected pituitary tumorBreastfeeding (relative, but often considered absolute)
| Precautions | Ovarian hyperstimulation syndrome (OHSS) risk, Multiple pregnancy risk, Ovarian enlargement and pain, Possible anaphylactic reactions, Tumor flare in gonadotropin-dependent tumors (e.g., prostate cancer) |
| Food/Dietary | Fasting (8-12 hours) is recommended before the test; avoid fatty meals, high-fiber foods, and alcohol on the test day as they may interfere with hormone response. |
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| Lactation Rating | L5 (Avoid) |
| Teratogenic Risk | Pregnancy Category X. Factrel (gonadorelin) is contraindicated in pregnancy due to risk of fetal harm. Use during first trimester may cause fetal abnormalities; second and third trimester risks include potential for hormonal disruption, though data limited. |
| Fetal Monitoring | Monitor pregnancy status before initiating therapy. Assess ovarian hyperstimulation syndrome if used for ovulation induction. No specific fetal monitoring required beyond standard prenatal care. |
| Fertility Effects | Used for ovulation induction; may improve fertility. Chronic use can cause pituitary desensitization and reduced gonadotropin release, potentially impairing fertility. Effects reversible upon discontinuation. |
| Clinical Pearls |
| FACTREL (gonadorelin hydrochloride) is a synthetic luteinizing hormone-releasing hormone (LHRH) used for diagnostic testing of pituitary gonadotropin reserve. Administer intravenously or subcutaneously; observe for transient flushing or hypotension. Contraindicated in hypersensitivity. For test interpretation, measure LH and FSH at 0, 30, and 60 minutes post-dose. |
| Patient Advice | This medication is used only for a diagnostic test, not for regular treatment. · You may experience temporary hot flashes, sweating, or a metallic taste. · Report any signs of severe allergic reaction (e.g., hives, difficulty breathing) immediately. · Avoid eating fatty meals or high-fiber foods on the test day as they may affect hormone levels. · Fasting is recommended for 8-12 hours before the test. · Inform your doctor about all other medications you are taking. |