NafarelinvsBuserelin

Molecular Formula

C₆₆H₈₃N₁₇O₁₃

Molecular Weight

1322.5 g/mol

Half-Life

Approximately 2-6 hours (varies by route of administration)

Bioavailability

~2-3% (intranasal)

CAS Number

86220-42-0

Molecular Formula

C₆₀H₈₆N₁₆O₁₃

Molecular Weight

1239.4 g/mol

Half-Life

2-4 hours (subcutaneous), 30-60 minutes (intranasal); longer for depot formulation (28-40 days)

Bioavailability

~1% (oral); ~10-15% (intranasal); ~95% (subcutaneous)

CAS Number

57773-65-6

Common

• Hot flashes and night sweats (happen in 90% of users)
• Mood changes including depression or anxiety
• Decreased sexual interest
• Vaginal dryness
• Headaches
• Nasal irritation (if using spray formulation)
• Breast tenderness
• Muscle aches and joint pain
• Weight gain or changes in body composition
• Nausea and upset stomach
• Sleep problems
• Emotional sensitivity and mood swings
• Allergic reactions (rare)
• Significant bone density loss with extended use
• Severe mood disorders requiring medical attention
• Hot flashes (flushes of heat and redness)
• Night sweats and chills
• Vaginal dryness and discomfort
• Mood depression or anxiety
• Changes in sexual desire
• Weight changes
• Headaches
• Muscle and joint aches
• Nasal irritation or sinus problems
• Breast tenderness or swelling
• Acne
• Sleep disturbances
• Nausea
• Fatigue
• Bone pain

Serious

• Severe allergic reaction

Evidence Level

Strong human trials (Phase 3 or FDA approved)

FDA Status

FDA approved for this use

Safety Overview

Nafarelin is FDA-approved with a well-established safety profile across decades of clinical use for endometriosis and precocious puberty. The most significant safety consideration is hypogonadism and bone density loss during prolonged therapy, requiring add-back therapy (norethindrone 0.4 mg daily) after 6 months to prevent osteoporosis. Common side effects—hot flashes, vaginal dryness, mood changes—are reversible upon discontinuation and typically diminish with continued use.

Contraindications

• xPregnancy (can harm fetus - must use non-hormonal birth control)
• xHypersensitivity to GnRH agonists
• xUndiagnosed vaginal bleeding
• xSevere osteoporosis or bone disease

Evidence Level

Strong human trials (Phase 3 or FDA approved)

FDA Status

FDA approved for other use

Safety Overview

Buserelin is an FDA-approved GnRH agonist with safety data from Phase 3 trials and decades of clinical use, but carries well-documented risks from intentional testosterone/estrogen suppression. The initial testosterone flare (first 2-3 weeks) can worsen prostate cancer symptoms and cause tumor flare pain in 10-20% of patients. Long-term use causes bone density loss of 2-3% annually, with vertebral fractures in 10-20% of long-term users. Cardiovascular risks include increased MI and stroke in men over 65. Hot flashes affect 40-80%, erectile dysfunction is nearly universal, and liver enzyme elevations occur in 5%. Nasal spray formulation causes local irritation in 20-30% of users.

Contraindications

• xPregnancy or breastfeeding
• xHypersensitivity to GnRH agonists
• xCertain bone diseases when long-term use is planned