How does it work?

Zoladex implant contains the active ingredient goserelin acetate, which is a type of medicine known as a gonadorelin (LHRH) analogue. It acts on the pituitary gland in the brain.

The pituitary gland produces and stores various hormones, including the sex hormones, luteinising hormone (LH) and follicle-stimulating hormone (FSH). In men, LH causes the testes to produce testosterone. FSH and testosterone cause the production of sperm by the testes. In women, FSH and LH cause the production of oestrogen by the ovaries and help control the menstrual cycle.

The amount of LH and FSH released from the pituitary gland is controlled by another hormone, called gonaderelin (LHRH). Gonadorelin acts on LHRH receptors in the pituitary gland, causing the release of LH and FSH and hence the subsequent production of testosterone in men and oestrogen in women.

Goserelin acetate is a synthetic form of gonaderelin. It acts on the LHRH receptors in the pituitary gland, in the same way as natural gonadorelin.

Initially, goserelin causes an increase in the amount of FSH and LH released from the pituitary gland. However, chronic administration of goserelin desensitises the pituitary gland. This means that it produces less and less FSH and LH, which in turn stops the production of oestrogens in women and testosterone in men. This reduction in the levels of sex hormone can be exploited to treat disorders that are linked to levels of oestrogen or testosterone.

The growth of some breast cancers is stimulated by oestrogen, and that of some prostate cancers by testosterone. Because these cancers are sensitive to the sex hormones, goserelin can be used in their treatment. Reducing the body's levels of these hormones causes the tumours to shrink. This treatment does not provide a cure, but rather improves quality of life and increases life expectancy.

The Zoladex implant is injected under the skin of the abdomen, from where it steadily releases the goserelin into the bloodstream over a four week period. An implant is injected every 28 days.

In women, goserelin is also used to treat endometriosis, a condition where tissue resembling the womb or uterus lining (endometrium) grows in other places in the body. The growth of this tissue is stimulated by oestrogen, so decreasing oestrogen levels with goserelin will stop the growth of this tissue, thereby relieving symptoms. When treating endometriosis, the implant is injected every 28 days for six months only. This course should not be repeated.

The effect of goserelin on endometrial tissue can also be used to thin the lining of the womb (endometrium) prior to endometrial surgery. In this case, one or two injections are used. The first injection may be repeated after 28 days for women with a large uterus, or to allow flexible timing of the surgery.

The growth of fibroids in the uterus is also stimulated by oestrogen, so goserelin is used to decrease oestrogen levels and hence decrease the size of fibroids. This medicine is used prior to surgery in women who have become anaemic due to their fibroids. When treating fibroids, the implant may be administered every 28 days for up to three months before surgery.

Zoladex is also used in assisted reproduction (IVF) in women who are having trouble conceiving due to problems with ovulation. In this case, one injection of Zoladex is given to desensitise the pituitary gland and stop the natural production of FSH and LH. This takes between one to three weeks. Synthetic FSH, LH and hCG (gonadotrophins) are then administered to artificially stimulate ovulation.

What is it used for?

• Prostate cancer.
• Breast cancer.
• Endometriosis.
• Thinning the lining of the womb (endometrium) prior to surgery (endometrial ablation or resection).
• Fibroids of the uterus (prior to surgery, in combination with iron in women who are anaemic).
• Preparing the pituitary gland before treatment with gonadotrophins to stimulate ovulation in fertility treatment (IVF).

Warning!

• In men with prostate cancer, goserelin may cause an initial temporary tumour 'flare' with symptoms such as urinary obstruction and bone pain, before the cancer begins to shrink. Some men may be particularly prone to these symptoms. If this applies to you, your doctor will also treat you with another type of anti-cancer medicine, known as an anti-androgen (eg cyproterone acetate or flutamide) to prevent this. The anti-androgen will be started three days before the goserelin and continued for the first three weeks of treatment.
• Your doctor may want to monitor your blood sugar levels while you are being treated with this medicine.

Use with caution in

• Men considered by their doctor to be at risk of an initial worsening of their tumour symptoms (tumour flare) when starting treatment.
• Men whose cancer has spread to the spine.
• Men with difficulty passing urine.
• Men with diabetes.
• Metabolic bone disease, eg osteoporosis (this medicine may cause a reduction in bone mineral density in both men and women).
• Fertility treatment in women with polycystic ovary syndrome.

Not to be used in

• Children.
• Pregnancy.
• Breastfeeding.
• Allergy to other LHRH analogues, eg buserelin, leuprorelin, triptorelin.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

• This medicine should not be used in women who are pregnant. Women who are being treated with this medicine for reasons other than fertility treatment must use a non-hormonal method of contraception, eg condoms, throughout the treatment. Seek further medical advice from your doctor.
• When this medicine is used in fertility treatment (IVF), the available evidence shows that it does not cause any abnormalities in egg development, or on the outcome of any pregnancy that results from the treatment.
• As it affects hormone levels, this medicine is not recommended for use during breastfeeding. Seek further medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

General side effects

• Bruising or pain at injection site.
• Hot flushes.
• Decreased sex drive.
• Sweating.
• Skin rashes.
• Pins and needles sensations (paraesthesia).
• Pain in the joints (arthralgia).
• Decrease in bone mineral density.
• Changes in blood pressure.
• Rarely, allergic reactions.
• Very rarely, damage to the pituitary gland due to sudden haemorrhage or decreased blood supply (pituitary apoplexy) following initial administration.

Side effects in women

• Headache.
• Mood changes, including depression.
• Vaginal dryness.
• Change in breast size.
• Development of fluid filled sacks (cysts) in the ovaries.
• Vaginal bleeding. This usually happens in the first month after starting treatment and usually stops on its own. Tell your doctor if the bleeding continues.
• When treating uterine fibroids, bleeding associated with fibroid degeneration may occur.
• Temporary increase in symptoms in women with breast cancer.
• Increase in the level of calcium in the blood in women with breast cancer. Signs of this may include feeling or being very sick, or being very thirsty. Tell your doctor if this happens.
• When Zoladex is used in combination with gonadotrophins for fertility treatment, ovarian hyperstimulation syndrome (OHSS) has been reported.
• Some women may start their menopause early while being treated with Zoladex, and their periods may not return when treatment is stopped.

Side effects in men

• Breast swelling and tenderness.
• Increase in blood sugar levels.
• Temporary increase in bone pain, pain in your lower back, or difficulty passing urine. Tell your doctor if this happens.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

This medicine is not known to affect other medicines. However, as with all medicines, it is important to let your doctor or pharmacist know what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, always check with your doctor or pharmacist before using other medicines while being treated with this one, to make sure the combination is safe.

Other medicines containing the same active ingredient