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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FACTREL (FACTREL).
| Breastfeeding | Not recommended during breastfeeding. Excretion into human milk unknown; M/P ratio not available. Possible effects on infant gonadotropin secretion. |
| 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 |
■ FDA Black Box Warning
No FDA boxed warning is present for Factrel.
| Serious Effects |
["Hypersensitivity to gonadotropin-releasing hormone or its analogs","Pregnancy","Undiagnosed abnormal vaginal bleeding","Ovarian cyst or enlargement not due to polycystic ovary syndrome"]
| 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)"] |
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| 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. |