Zoladex (goserelin) is a hormone therapy medicine used to treat:

• Prostate cancer (to lower testosterone levels and slow cancer growth)
• Breast cancer (in premenopausal women, to suppress oestrogen production)
• Endometriosis
• Uterine fibroids (prior to surgery)
• Fertility treatment (to control the timing of ovulation)

Goserelin is a GnRH (gonadotrophin-releasing hormone) agonist. It initially causes a brief rise in sex hormone levels, but with continued use it suppresses the signals from the pituitary gland that stimulate the production of testosterone (in men) or oestrogen (in women). This hormone suppression slows or stops the growth of hormone-sensitive cancers and reduces hormone-driven conditions such as endometriosis.

Zoladex is given as a subcutaneous implant: a small rod inserted under the skin of the lower abdomen by a healthcare professional. A local anaesthetic is used to numb the area before injection.

The implant releases goserelin slowly over the treatment period:

• 3.6 mg implant: inserted every 28 days
• 10.8 mg implant: inserted every 12 weeks (three months)

You do not need to do anything after the implant is inserted. The implant is biodegradable and fully dissolves on its own; there is no need for removal.

Keep all scheduled appointments. Missing an implant can allow hormone levels to rise and undermine treatment.

Your implant is administered in a clinic on a set schedule. Contact your doctor as soon as possible if you have missed an appointment, as the implant's effect can wear off if intervals are extended.

Because Zoladex is given in a clinical setting as a controlled implant, overdose is not applicable. Contact your doctor if you have concerns.

Storage is managed by the clinic. Zoladex implants are stored at room temperature (below 25°C) and must not be frozen.

Side effects relate to the reduction in sex hormone levels.

In men and women (common):

• Hot flushes and sweating
• Loss of sex drive
• Mood changes
• Fatigue

In men (common):

• Erectile dysfunction
• Breast tenderness or enlargement (gynaecomastia)

In women (common):

• Vaginal dryness
• Menstrual irregularities or absence of periods (amenorrhoea) during treatment

Long-term effects:

• Bone thinning (osteoporosis): with prolonged hormone suppression, bone density can decrease. Calcium, vitamin D, and weight-bearing exercise are important preventive measures. Bone density scans may be recommended

At treatment start:

• Initial testosterone flare (in men): for the first 1 to 2 weeks, testosterone and PSA may rise before falling. This can temporarily worsen bone pain or urinary symptoms in men with advanced prostate cancer. Your doctor may prescribe an anti-androgen for the first few weeks to minimise this flare

Tell your doctor about any new or worsening symptoms, particularly bone pain or urinary symptoms at the start of treatment.

Zoladex works by suppressing hormone levels and has minimal pharmacokinetic drug interactions.

However:

• Medicines that affect heart rhythm (QT-prolonging drugs): GnRH agonists can prolong the QT interval. Tell your doctor if you take antiarrhythmics or other QT-prolonging medicines
• Diabetic medicines: hormone changes can affect blood sugar control. Monitor more frequently

Always tell all your healthcare providers that you are on Zoladex hormone therapy.

How does Zoladex compare to Firmagon for prostate cancer?

Both Zoladex (a GnRH agonist) and Firmagon (a GnRH antagonist) lower testosterone to treat prostate cancer, but by different mechanisms. Zoladex causes an initial testosterone surge (the 'flare') for the first 1 to 2 weeks before levels fall. Firmagon suppresses testosterone immediately with no initial flare. For men with severe bone pain from prostate cancer spread to the bones, the flare with Zoladex can worsen symptoms temporarily. In such patients, Firmagon may be preferred. For most other patients, both are effective and the choice depends on individual factors.

Will my periods come back after stopping Zoladex?

For most premenopausal women, periods return within a few weeks to months after the last implant. However, if you are near menopause, periods may not return. Fertility may also return after stopping, which is an important consideration if you were using Zoladex for a non-cancer indication. Discuss contraceptive needs with your doctor, as you should not rely on Zoladex for contraception and should use non-hormonal contraception during treatment.

Ace provides accurate and independent information medically reviewed on prescription medications. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment.