AbarelixvsDegarelix

Molecular Formula

C₇₂H₉₅ClN₁₄O₁₄

Molecular Weight

1416.1 g/mol

Half-Life

Approximately 13 days

Bioavailability

~100% (intramuscular depot injection)

CAS Number

183552-38-7

Molecular Formula

C₈₂H₁₀₃ClN₁₈O₁₆

Molecular Weight

1632.3 Da

Half-Life

~53 days (median terminal half-life)

Bioavailability

100% (subcutaneous injection)

CAS Number

214766-78-6

Common

• Mild discomfort at treatment site
• Hot flashes and sweating
• Decreased libido and sexual dysfunction
• Increased liver enzymes
• Injection site reactions (pain, redness, swelling)
• Abdominal pain and gastrointestinal symptoms
• Headache and dizziness
• Weight changes
• Gynecomastia (breast tissue enlargement)
• Bone density loss with long-term use

Serious

• Severe allergic reaction

Common

• Mild discomfort at treatment site
• Injection site pain (28% of patients)
• Injection site redness or erythema (17%)
• Hot flashes (26% experience them)
• Increased liver enzymes and gamma-glutamyltransferase (10%)
• Weight gain (9%)
• Hypertension or elevated blood pressure (6%)
• Back pain (6%)
• Chills (5%)
• Constipation (5%)
• Urinary tract infection (5%)
• Injection site swelling (6%)
• Injection site induration or hardness (4%)
• Decreased sex drive and erectile dysfunction
• Gynecomastia (breast tissue growth)
• Testicular atrophy (shrinking)

Serious

• Severe allergic reaction

Evidence Level

Strong human trials (Phase 3 or FDA approved)

FDA Status

FDA approved for other use

Safety Overview

Abarelix carries significant safety concerns primarily related to histamine release reactions, which led to its voluntary withdrawal from the U.S. market in 2006. Serious allergic responses including anaphylaxis, flushing, and hypotension have been documented. Long-term use poses substantial risks of bone density loss, cardiovascular effects from hormonal suppression, and metabolic complications including weight gain and altered lipid profiles. Liver enzyme elevations occur in 5-10% of patients. All use requires intensive medical supervision with regular monitoring of testosterone levels, liver function, bone density, and cardiovascular markers.

Contraindications

• xPregnancy or lactation
• xSevere hypersensitivity reactions to peptide therapeutics
• xHistory of anaphylaxis with similar compounds

Evidence Level

Strong human trials (Phase 3 or FDA approved)

FDA Status

FDA approved for this use

Safety Overview

Degarelix is an FDA-approved GnRH antagonist with safety data from Phase 3 trials and post-market use in prostate cancer treatment. Advantages over GnRH agonists include absence of testosterone flare, allowing rapid castration without initial symptom surge. Primary safety concerns relate to intentional hormone suppression: hot flashes occur in 40-70% of men, erectile dysfunction in 40-60%, bone density loss of 2-3% annually, and cardiovascular risks in patients >65 years. Injection site reactions (erythema, induration) occur in 20-30% of patients and can be severe in a small percentage. Liver enzyme elevations appear in 5% of patients. QT prolongation potential exists and cardiac monitoring is recommended in susceptible patients.

Contraindications

• xHistory of severe hypersensitivity to degarelix
• xAllergy to any product components (mannitol or other additives)
• xActive untreated severe anaphylaxis risk