Cancer drugs A to Z list
Triptorelin is a type of You pronounce it as trip-toe-reh-lin.
It is a treatment for breast cancer.
You might have triptorelin for with other hormone treatments if you have not gone through the menopause ( ). The type of triptorelin used for breast cancer is called Decapeptyl SR.
Triptorelin is also used to treat prostate cancer.
Triptorelin for prostate cancer
Some breast cancers depend on to grow. Oestrogen is a type of that your body naturally produces. This type of breast cancer is called oestrogen receptor positive (ER positive) breast cancer. Triptorelin blocks messages from the brain that normally tell the body to make oestrogen. By blocking these messages, triptorelin reduces the amount of oestrogen in the body. This can slow down or stop the growth of the cancer.
Find out more about how hormone therapy works
You have triptorelin for breast cancer as an injection into a muscle (intramuscular), usually in your buttock or upper thigh.
You have a triptorelin injection every 4 weeks. Your nurse or doctor will go through how long you should expect to continue having triptorelin, it is usually up to 5 years.
You have blood tests before and during your treatment. They check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.
Lowering sex hormone levels can also affect your bone strength over time. Your doctor may want you to have a test (called a ) before you start treatment, especially if you're at risk of
Side effects can vary from person to person. They also depend on what other treatment you are having.
Your doctor, nurse, or pharmacist will go through the possible side effects. They will monitor you closely during treatment and check how you are at your appointments. Contact your advice line as soon as possible if:
you have severe side effects
your side effects aren’t getting any better
your side effects are getting worse
We haven't listed all the side effects here. Talk to your healthcare team if you have any new symptoms that you think might be a side effect of your treatment.
Remember it is very unlikely that you will have all of these side effects, but you might have some of them at the same time.
Triptorelin (Decapeptyl SR) can be used for early stage breast cancer in women. It is also sometimes used to treat problems with the female reproductive system.
These side effects happen in more than 10 in 100 people (more than 10%). You might have one or more of them. They include:
Tell your healthcare team if you keep getting headaches. They can give you painkillers to help.
You may experience mood problems, such as depression or anxiety. Speak to your doctor or nurse if you are feeling low or having extreme changes in your mood.
Talk to your doctor if you have this. You might be able to have some treatments to help with low sex drive.
You may have problems with sleeping, such as difficulty sleeping, this is called insomnia. It can help to change a few things about how you try to sleep. Try to go to bed and get up at the same time each day and spend some time relaxing before you go to bed. Some light exercise each day may also help.
You might notice skin changes, such as dryness, itching and flaking on your face, neck and trunk. Or you may get acne.
Tell your doctor if you have any rashes or itching. Don't go swimming if you have a rash because the chlorine in the water can make it worse.
If your skin gets dry or itchy, using unperfumed moisturising cream may help. Check with your doctor or nurse before using any creams or lotions. Wear a high factor sun block if you’re going out in the sun.
You may have some non cancerous lumps and breast changes (breast disorders). Occasionally people have breast pain.
Feeling sick is usually well controlled with anti sickness medicines. Avoiding fatty or fried foods, eating small meals and snacks, drinking plenty of water, and relaxation techniques can all help.
It is important to take anti sickness medicines as directed by your doctor or pharmacist, even if you don’t feel sick. It is easier to prevent sickness rather than treating it once it has started.
You may have weakened bones that are fragile (osteoporosis) and occasionally break. Or you might develop a condition that affects your bones, joints, muscles, ligaments, tendons or nerves (musculoskeletal system), causing you to feel pain, stiffness and limiting your movement.
You might leak pee (urinate) or be unable to control when you pee.
Tell your doctor or nurse if you have headaches, nosebleeds, blurred or double vision or shortness of breath. You have your blood pressure checked regularly.
You may have hot flushes and sweat a lot. We have some tips for coping with hot flushes in women. This information also includes some of the possible treatments. Talk to your doctor if your hot flushes are hard to cope with. They might be able to prescribe some medicines to help.
Tiredness (fatigue) and weakness can happen during and after treatment. Doing gentle exercises each day can keep your energy up. Don't push yourself, rest when you start to feel tired and ask others for help.
You might have dryness, bleeding or spotting blood from the vagina. You may feel pain during or after sex. Rarely you might bleed during sex or have vaginal discharge. This treatment might make the ovaries overactive. Your ovaries might get bigger. Or you might have pain.
Rarely you might have a condition when the wall between the bladder and the vagina gets weak. This can cause the bladder to drop or sag into the vagina. This is called a cystocele or prolapsed bladder. Rarely you could also have pain and cramps in your tummy (abdomen) during your period, have abnormal or very heavy periods. Let your team know if you have any of these symptoms.
These side effects happen in between 1 and 10 out of every 100 people (between 1 and 10%). You might have one or more of them. They include:
an allergic reaction that can cause a rash, shortness of breath, redness or swelling of the face and dizziness - some allergic reactions can be life threatening, alert your nurse or doctor if notice any of these symptoms
dizziness
redness, inflammation or tenderness at the injection site
weight gain
swollen legs or arms due to fluid build up (oedema)
high blood sugar levels can cause headaches, feeling thirsty and blurred vision. You may need to check your blood glucose levels more often if you have diabetes
a blockage in your artery, such as a blood clot (embolism)
pain or discomfort in different parts of your body including your tummy (abdomen) and rarely, your back, legs or arms. You might also have muscle spasms.
This side effects happens in fewer than 1 in 100 people (fewer than 1%). You might have one or more of them. They include:
a severe allergic reaction
problems with your sight or dry eyes
the feeling of the room spinning or moving around you (vertigo)
being sick
hair loss or excess hair
breathlessness
reduced appetite
feeling your heartbeat in your chest (palpitations)
a heart condition when your heart doesn’t get enough oxygen, which can lead to shortness of breath and chest pain (myocardial ischemia)
the brain not getting enough oxygen (cerebral ischemia)
bleeding in the brain or spinal cord
weight loss
nosebleeds
feeling disorientated
taste changes
loss of sensation
a build up of fluid in the body
fainting
forgetfulness and finding it difficult to remember things
finding it difficult to focus
unusual skin sensations such as tingling, numbness or pins and needles
parts of your body shaking (tremors)
passing wind (flatulence)
mouth ulcers
bloated tummy (abdomen)
dry mouth
nail problems
A severe allergic reaction is a known side effect. But there isn't enough information to work out often this might happen.
Tell your doctor or nurse immediately any time you feel unwell. Or if you have symptoms that include a skin rash, itching, swelling of the lips, face or throat, breathing difficulties, fever and chills.
Men can have triptorelin (Decapeptyl SR) for breast cancer or prostate cancer. The side effects listed below are also for men with prostate cancer. So they might not all apply to you.
These side effects happen in more than 10 in 100 people (more than 10%). You might have one or more of them. They include:
Talk to your doctor if you have this. You might be able to have some treatments to help with low sex drive.
You might have unusual skin sensations such as numbness, tingling, prickling or burning in your legs. It can feel like pins and needles.
Let your doctor or nurse know if you have this.
You may have hot flushes and sweat a lot. We have some tips for coping with hot flushes in men. This information also includes some of the possible treatments. Talk to your doctor if your hot flushes are hard to cope with. They might be able to prescribe some medicines to help.
You might have back pain. Occasionally you may have pain in your , muscles, hands or feet. Rarely you could have tummy (abdomen) pain, bone or joint pain, breast pain, testicle pain, joint stiffness, muscle cramps, aches and pain.
You might have problems getting an erection (impotence). Talk to your doctor or nurse if you have this. There are treatments that can help, such as medicines, vacuum pumps and injections or pellets. Your doctor or nurse can refer you to a specialist in this area.
Tiredness and weakness (fatigue) can happen during and after treatment. Doing gentle exercises each day can keep your energy up. Don't push yourself, rest when you start to feel tired and ask others for help.
Feeling sick is usually well controlled with anti sickness medicines. It might help to avoid fatty or fried foods, eat small meals and snacks and take regular sips of water. Relaxation techniques might also help.
It is important to take anti sickness medicines as prescribed even if you don’t feel sick. It is easier to prevent sickness rather than treat it once it has started.
You may have weakened bones that are fragile and occasionally break (osteoporosis). Or you might develop a condition that affects your musculoskeletal system (bones, joints, muscles, ligaments, tendons and nerves), causing you to feel pain, stiffness and limiting your movement.
If you have difficulty sleeping, it can help to change a few things about how you try to sleep. Try to go to bed and get up at the same time each day and spend some time relaxing before you go to bed. Some light exercise each day may also help.
Tell your doctor or nurse if you’re feeling depressed. They can arrange for you to talk to someone and give treatment if necessary.
You might occasionally leak pee (urine) or be unable to control when you pee. Rarely you might find it difficult to pee. Or need to get up at night to pee.
You may have pain during or after sex. Talk to your doctor or nurse if you are experiencing this.
Tell your doctor or nurse if you have headaches, nosebleeds, blurred or double vision or shortness of breath. You have your blood pressure checked regularly.
These side effects happen in between 1 and 10 out of every 100 people (between 1 and 10%). You might have one or more of them. They include:
an allergic reaction that can cause a rash, shortness of breath, redness or swelling of the face and dizziness - some allergic reactions can be life threatening, alert your nurse or doctor if notice any of these symptoms
mood changes
dizziness
headaches
dry mouth
general swelling due to fluid build up (oedema)
redness, inflammation or tenderness at the injection site
weight gain
high blood sugar levels can cause headaches, feeling thirsty and blurred vision. You may need to check your blood glucose levels more often if you have diabetes
a blockage in your artery, such as a blood clot (embolism)
These side effects happen in fewer than 1 in 100 people (fewer than 1%). You might have one or more of them. They include:
high level of in the blood
loss of appetite (anorexia)
pain and swelling in the joints, usually the big toe (gout)
high levels of fat in the blood (high cholesterol)
increased appetite
feeling irritable
sight problems
ringing in ears (tinnitus)
the feeling of the room spinning or moving around you (vertigo)
feeling your heartbeat in your chest (palpitations)
shortness of breath
nosebleeds
constipation
diarrhoea
being sick (vomiting)
acne
hair loss
having a rash or red, itchy skin
an increase in breast tissue
testicles getting smaller
severe shivering (rigors)
feeling very drowsy
liver changes that are usually mild and unlikely to cause symptoms. They usually go back to normal when treatment finishes. You have regular blood tests to check for any changes in the way your liver is working
kidney changes – you will have regular blood tests to check for this
a heart condition when your heart doesn’t get enough oxygen, which can lead to shortness of breath and chest pain (myocardial ischemia)
the brain not getting enough oxygen (cerebral ischemia)
bleeding in the brain or spinal cord
a severe allergic reaction that can include a skin rash, itching, swelling of the lips, face or throat, breathing difficulties, fever and chills. This is very rare, tell your doctor or nurse immediately if at any time you feel unwell
We have more information about side effects and tips on how to cope with them.
Cancer drugs can interact with medicines, herbal products, and some food and drinks. We are unable to list all the possible interactions that may happen. An example is grapefruit or grapefruit juice which can increase the side effects of certain drugs.
Tell your healthcare team about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies. Also let them know about any other medical conditions or allergies you may have.
This treatment might harm a baby developing in the womb, but there is not enough information to know for sure. It is important not to become pregnant or get someone pregnant while you're having treatment and for a few months afterwards.
Talk to your doctor or nurse about effective contraception before starting treatment. Let them know straight away if you or your partner become pregnant while having treatment.
Don’t breastfeed during this treatment because the drug may come through into your breast milk.
If you are having tests or treatment for anything else, always mention your cancer treatment. For example, if you are visiting your dentist.
For further information about this treatment and possible side effects go to the electronic Medicines Compendium (eMC) website. You can find the patient information leaflet on this website.
You can report any side effect you have to the Medicines and Healthcare products Regulatory Agency (MHRA) as part of their Yellow Card Scheme.
Last reviewed: 23 Jul 2025
Next review due: 23 Jul 2028
Find out about breast cancer, including symptoms, diagnosis, treatment, survival, and how to cope with the effects on your life and relationships.
Cancer drugs have side effects and these can vary from person to person. But there are things that you can do to help you cope.
Coping with cancer can be difficult. There is help and support available. Find out about the emotional, physical and practical effects of cancer and how to manage them.
Hormone therapy blocks or lowers the amount of hormones in the body to stop or slow down the growth of cancer.

About Cancer generously supported by Dangoor Education since 2010. Learn more about Dangoor Education
What to ask your doctor about clinical trials.
Meet and chat to other cancer people affected by cancer.
Questions about cancer? Call freephone 0808 800 40 40 from 9 to 5 - Monday to Friday. Alternatively, you can email us.