Triptorelin (Decapeptyl® SR, Gonapeptyl Depot®)

Triptorelin is a hormonal therapy drug used to treat prostate cancer. It’s best to read this with our general information about prostate cancer.

You have triptorelin as an injection into the muscle (intramuscularly) or just under the skin (subcutaneously). Your cancer doctor or nurse will tell you how often you will have it.

Like all hormonal therapy drugs, triptorelin can cause side effects. Some of these can be serious so it’s important to read the detailed information below. How hormonal therapy affects people varies from person to person. Your healthcare team can talk to you more about this and give you advice on how to manage any side effects.

Tell your doctor or nurse straight away if you feel unwell or have severe side effects, including any we don’t mention here. If you need to see a health professional for any reason other than cancer, always tell them that you are having this treatment.

How triptorelin works

Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies interfere with the way hormones are made or how they work in the body.

Most prostate cancers need the hormone testosterone in order to grow. Almost all testosterone in men is made by the testicles. A very small amount is made by the adrenal glands, which sit above the kidneys.

Triptorelin stops the testicles from making testosterone. This reduces testosterone levels and may shrink the prostate cancer or stop it growing.

When triptorelin is given

Triptorelin can be used on its own or with other types of treatment. It may be used before or after surgery or radiotherapy. It may also be used to control prostate cancer that has spread to other parts of the body (advanced or metastatic prostate cancer).

Triptorelin can be given for months or years, depending on your situation. Some men with advanced prostate cancer may have intermittent therapy with triptorelin. This involves having triptorelin treatment for a few months until the cancer is at a very low level. This is measured by a blood test called a PSA test. You then have a break from treatment and restart triptorelin when needed.

Your cancer doctor or nurse will explain how long you will have triptorelin for.

How triptorelin is given

Triptorelin is given as an injection. It can be given as a monthly injection, or as a longer-acting injection every three or six months. There are two types of triptorelin, Decapeptyl® and Gonapeptyl®. Both types can be given into the muscle (intramuscularly). Gonapeptyl® can also be given just under the skin (subcutaneously).

Tell your doctor or nurse if you are taking any medicines to thin your blood as this may increase any bruising from the injection.

The injections will usually be given by your practice nurse at your doctor’s surgery. If you’re not able to visit the surgery, a district nurse can give you the injection at home. If an injection is delayed by 2-3 days, this should not affect how well the treatment works. But you should try to have your injections on time if possible.

Some people may find the injection slightly uncomfortable and notice redness or a darker colour around the area afterwards. You may have a local anaesthetic cream applied before the injection to reduce any discomfort.

Possible side effects of triptorelin

We explain the most common side effects of triptorelin here. We also include some rarer side effects. You may get some of the side effects we mention, but you are very unlikely to get all of them. If you are having other drugs as well, you may have some side effects that we don’t list here.

You will see a doctor or nurse regularly while you have this treatment. Always tell your doctor or nurse about the side effects you have. They can prescribe drugs to help control them and give you advice about managing them.

More information about this drug

We’re not able to list every side effect for this treatment here, particularly the rarer ones. For more detailed information you can visit the electronic Medicines Compendium.

Allergic reaction

Sometimes, triptorelin may cause an allergic reaction within a few hours of being given. Usually this is mild, but rarely the reaction can be more serious. Signs of a reaction can include:

  • raised itchy rash
  • feeling flushed
  • feeling dizzy or short of breath
  • having pain in your back, tummy or chest
  • feeling generally unwell.

If you develop any of these symptoms, contact your doctor straight away for advice.

Tumour flare

There may be a temporary increase in testosterone levels in the first few days or weeks after starting triptorelin. This may make symptoms caused by the cancer worse. Doctors call this tumour flare. Your doctor may prescribe a hormonal therapy for you to take as a tablet to prevent or reduce tumour flare. You usually begin taking the tablets before starting treatment with triptorelin and continue with them for a few weeks after.

If you notice any increase in symptoms in the first month after starting triptorelin, let your doctor know. In particular, if you have problems passing urine, back pain, or numbness or tingling in your legs, tell your doctor straight away.

Hot flushes and sweats

Hot flushes and sweats are common, and can be mild or more severe. During a flush you feel warmth in your neck and face, and your skin may redden. Mild flushes last from a few seconds to about a couple of minutes. More severe flushes can last for 10 minutes or more. You may have sweats, and then feel cold and clammy. Some people feel anxious or irritable during a hot flush.

There are things you can do to try to reduce flushes. These include cutting down on nicotine, alcohol and hot drinks that contain caffeine, such as tea and coffee.

If hot flushes are troublesome, your doctor can prescribe drugs to help reduce them.

Hot flushes and sweats may happen less as your body adjusts to hormonal treatment. They usually stop completely a few months after treatment finishes.

We have more information about hot flushes.

Sexual effects

Most men lose their sex drive and have erection difficulties during hormonal therapy. These often return to normal after you stop taking the drug, but some men continue to have difficulties after treatment has finished. Your doctor can prescribe treatments to help with erection difficulties, but these don’t affect sex drive.

If you need support coping with sexual difficulties, your nurse or doctor can give you information and refer you for specialist support services.


Tiredness is a common side effect. There is evidence that exercising and doing resistance training (such as lifting weights) at least twice a week can reduce tiredness in men on hormonal therapy. It’s important to get medical advice before starting exercise. Ask your doctor or nurse what is safe to do.

If tiredness makes you feel sleepy, don’t drive or operate machinery.


Headaches can usually be relieved with painkillers such as paracetamol. Tell your doctor or cancer nurse if headaches are troublesome.

Skin changes

You may find that your skin gets dry. Some men develop a skin rash but this is usually mild and often gets better without treatment. Tell your doctor if you notice any skin changes.

Dizziness, blurred vision, drowsiness

Sometimes, triptorelin can cause dizziness, blurred vision or drowsiness. Don’t drive or operate machinery if you have these side effects.

Feeling sick

Triptorelin can make you feel sick (nausea), but this is usually mild. If it doesn’t improve, your doctor can prescribe anti-sickness drugs.

Possible side effects of long-term triptorelin treatment

Weight gain and loss of muscle strength

You may gain weight, particularly around your waist, and you may lose some muscle strength. Eating a healthy diet and exercising regularly can help control your weight. Resistance exercises, such as lifting weights, may help you to reduce loss of muscle strength. Ask your doctor or nurse for advice.

Mood changes

You may experience mood swings. Some men can feel low or depressed after taking triptorelin for several months or more. Tell your doctor if you notice mood changes.

Memory and concentration

You may notice changes in your memory or ability to concentrate. Try using a notebook, sticky notes and a calendar to help you keep track of things. Talk to your doctor if you’re having problems.

Breast swelling or tenderness

You may notice breast swelling or tenderness. This is called gynaecomastia. Your doctor can advise you on how this can be prevented or treated.

Bone thinning (osteoporosis)

Taking triptorelin for a few years increases your risk of bone thinning (osteoporosis), which can increase your risk of a broken bone (fracture). Your doctor can give you advice on how this can be monitored and treated.

Regular walking and resistance exercises, such as lifting weights, can help to keep your bones strong. Eating a healthy diet, not smoking and staying within the recommended limits for alcohol will also help to protect your bones.

Let your doctor know if you have any discomfort in your bones or joints. We have more information about bone health.

Risk of heart changes and diabetes

There may be an increased risk of developing heart disease, changes in heart rhythm or diabetes when taking triptorelin. But the benefits of hormonal treatment generally outweigh the possible risks. You can talk to your specialist about the possible risks and benefits in your situation. It’s important to tell your doctors if you have ever had heart rhythm problems or if you’re taking any medicines for this.

You can help reduce your risk of heart disease and diabetes by:

  • not smoking
  • eating a healthy diet
  • staying within the recommended limits for alcohol
  • keeping to a healthy weight
  • being physically active.

Less common side effects of triptorelin

Blood clot (thrombosis)

Triptorelin may increase your risk of getting a blood clot. If you have any pain, redness or swelling in an arm or leg, or experience breathlessness or chest pain, let your doctor know immediately.

Always let your doctor or nurse know about any side effects you have. There are usually ways in which they can be controlled or improved.

Other information about triptorelin

Other medicines

Triptorelin can interact with other drugs. This includes medicines you can buy in a shop or chemist. Tell your doctor about any medicines you are taking, including ones you can buy for yourself, complementary therapies, vitamins and herbal drugs.

Medical treatment

If you need to go into hospital for any reason other than cancer, always tell the doctors and nurses that you are taking triptorelin. Explain you are taking hormonal therapy that no one should stop or restart without advice from your cancer doctor. Tell them the name of your cancer doctor so they can ask for advice.