📋 Clinical Overview

Goserelin acetate is a synthetic decapeptide analogue of gonadotropin-releasing hormone (GnRH). The 10.8 mg formulation is a long-acting, subcutaneous depot implant administered every 12 weeks. It acts as a potent GnRH agonist, initially stimulating then profoundly suppressing the pituitary-gonadal axis, leading to a chemical castration state with reduced levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and sex steroids (testosterone or estradiol).

💊 Dosage & Administration

Adult: 10.8 mg administered as a single subcutaneous implant into the anterior abdominal wall every 12 weeks (84 days). For endometriosis/fibroid treatment, duration is usually limited to 6 months (i.e., two injections).
Pediatric: Not recommended for children. Use for central precocious puberty is off-label and typically uses other GnRH agonists with more pediatric data.
Renal Adjusment: No specific dosage adjustment recommended for mild to moderate renal impairment. Use with caution in severe renal impairment (creatinine clearance <30 mL/min) as limited data exists.
Hepatic Adjusment: No specific dosage adjustment recommended. Use with caution in severe hepatic impairment.
Instruction: For subcutaneous use only. Using sterile technique, administer into the anterior abdominal wall. The area should be cleaned with an alcohol swab. The implant is supplied in a pre-filled syringe with a 16-gauge hypodermic needle. After administration, apply pressure to the site. Rotate injection sites with each administration. The implant is not to be removed as drug release is controlled by biodegradation.

⚠️ Contraindications

Hypersensitivity to Goserelin acetate, other GnRH agonists, or any excipients in the depot
Pregnancy (Category D) and women who may become pregnant during therapy
Breastfeeding mothers
Undiagnosed abnormal vaginal bleeding

🔬 Mechanism of Action

Goserelin is a potent agonist of GnRH receptors in the anterior pituitary. Continuous administration (as opposed to physiological pulsatile release) leads to an initial stimulation (flare) followed by a profound and reversible down-regulation of GnRH receptors. This results in desensitization of the pituitary gonadotroph cells, inhibiting the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The subsequent suppression of gonadal steroidogenesis leads to a hypogonadal state (chemical castration).

🤕 Side Effects

Hot flushes (flashes) - very common (>70% in men, >90% in women)
Decreased libido
Erectile dysfunction (men)
Headache
Sweating
Pain, bruising, or erythema at injection site
Vaginal dryness, dyspareunia, breast atrophy (women)
Gynecomastia or breast tenderness/pain (men)
Mood swings, emotional lability, depression

🤰 Special Populations

Pregnancy: CONTRANDICATED - Category D. May cause fetal harm based on mechanism. Can cause fetal loss or teratogenicity. Exclude pregnancy before starting. Women of childbearing potential must use non-hormonal contraception during and for 12 weeks after treatment.

Lactation: CONTRANDICATED. It is not known if goserelin is excreted in human milk, but due to potential for serious adverse reactions in the nursing infant, breastfeeding should be discontinued during therapy.

Alcohol: No known direct interaction. However, alcohol may exacerbate certain side effects like hot flushes, depression, or liver enzyme changes.

Driving: May cause fatigue, dizziness, or visual disturbances. Patients should be cautioned about operating machinery or driving until they know how the drug affects them.

🔄 Drug Interactions

Drugs that prolong QT interval (e.g., Class Ia/III antiarrhythmics, certain antipsychotics, antibiotics): Additive risk of QT prolongation and cardiac arrhythmias. Major
Other hormonal therapies (e.g., estrogens, androgens, other GnRH analogues): May interfere with the intended therapeutic effect of goserelin. Concomitant use not recommended unless part of a specific protocol (e.g., initial anti-androgen cover). Major
Corticosteroids (chronic use): Additive risk of bone mineral density loss and osteoporosis. Moderate
Drugs metabolized by CYP450 enzymes: Goserelin is not a significant inducer or inhibitor of CYP enzymes. No clinically significant pharmacokinetic interactions expected. Minor

🔁 Alternatives to Gonapeptyl (Note: This is Triptorelin, a different GnRH agonist. Included for context, but NOT Goserelin)

Same composition (Goserelin acetate (10.8mg)), different brands:

Zoladex Gosrelin Gosupro