Venetoclax (Venclyxto®)

You take venetoclax as tablets (orally). It can be given on its own or with other cancer drugs.

During treatment you usually see a cancer doctor, a cancer nurse or specialist nurse, and a specialist pharmacist. This is who we mean when we mention doctor, nurse or pharmacist in this information.

You will have your blood checked regularly during treatment. A nurse or person trained to take blood (phlebotomist) will take a blood sample from you. This is to check that your blood cells are at a safe level to have treatment.

You take venetoclax tablets once a day. You start on a low dose. The dose is gradually increased. This helps to reduce the risk of a side effect called tumour lysis syndrome.

Your nurse, doctor or pharmacist will discuss your treatment plan with you. They will give you the venetoclax tablets to take at home if needed. You may be given tablets of different strengths. They will explain the dose of tablets to take each day. They may give you a copy of the treatment plan to take home with you. Always take the tablets exactly as explained. This is important to make sure they work as well as possible for you.

You usually take venetoclax in the morning. This is because, to start with, you have blood tests during the day after each dose to check it is safe to continue treatment. Your doctor will tell you when your blood will be checked.

Your nurse or pharmacist may also give you anti-sickness drugs and other medicines to take home. 

You should take venetoclax tablets with or after food. Swallow them whole with a glass of water. Do not chew, break or crush them. Take them at the same time every day. 

During treatment with venetoclax, you should avoid grapefruit, star fruit and Seville oranges. This is because they can affect how venetoclax works. You should avoid:

• drinking the juice of these fruits
• eating food that contains them
• taking supplements that might contain them.

If you forget to take the tablets, you can take the missed dose up to 8 hours late. If you miss a dose by more than 8 hours, just take the next dose at the usual time. Do not take a double dose. Tell your doctor or nurse. 

Other things to remember about your tablets:

• Keep them in the original package and at room temperature, away from heat and direct sunlight.
• Keep them safe and out of sight and reach of children. 
• Read the label or check the instructions you have been given to check the strength and how many tablets to take.
• If you are sick just after taking the tablets, contact the hospital. Do not take another dose.
• If your treatment is stopped, return any unused tablets to the pharmacist.

This treatment can reduce the number of white blood cells in your blood. These cells fight infection. If your white blood cell count is low, you may be more likely to get an infection. A low white blood cell count is called neutropenia.

An infection can be very serious when the number of white blood cells is low. It is important to get any infection treated as soon as possible. If you have any of the following symptoms, contact the hospital straight away on the 24-hour number:

• a temperature above 37.5°C 
• a temperature below 36°C
• you feel unwell, even with a normal temperature
• you have symptoms of an infection.

Symptoms of an infection include:

• feeling shivery and shaking
• a sore throat
• a cough
• breathlessness
• diarrhoea
• needing to pass urine (pee) often, or discomfort when you pass urine.

It is important to follow any specific advice your cancer treatment team gives you.

You will have regular blood tests during treatment. If your white blood cell count is low, your doctor may stop your treatment for a short time, until your cell count increases. Sometimes they will reduce the dose of your treatment.

If you have TLS, it is very important it is treated early.

Contact the hospital straight away on the 24-hour contact number if you have symptoms that could be linked to TLS. These include: 

• feeling very hot (feverish) or have chills, and feeling sick
• pain in your joints or muscles 
• feeling breathless or having an irregular heartbeat
• dark or cloudy urine 
• feeling confused
• pain or swelling in your tummy 
• fits or seizures. 

These symptoms can be caused by different things. They may not be caused by TLS, but it is important to get them checked. 

You will have blood tests to check for TLS. Your doctor will talk to you about how to prevent or manage TLS. You can read more about this in our information on how venetoclax is given.

Feeling tired is a common side effect of this treatment. It is often worse towards the end of treatment and for some weeks after it ends. Try to pace yourself and plan your day so you have time to rest. Gentle exercise, like short walks, can help you feel less tired. 

If you feel sleepy, do not drive or use machinery.

This treatment may cause diarrhoea. Diarrhoea means passing more stools (poo) than is normal for you, or having watery or loose stools. You may also have stomach cramps. If you have a stoma, it may be more active than usual. 

If you are passing loose stools 3 or more times a day and this is not normal for you, contact the hospital as soon as possible on the 24-hour number. Follow the advice they give you about:

• taking anti-diarrhoea medicines 
• drinking enough fluids to keep you hydrated and to replace lost salts and minerals
• any changes to your diet that might help. 

They might also ask you for a specimen of your stool to check for infection.

This treatment can reduce the number of red blood cells in your blood. Red blood cells carry oxygen around the body. If the number of red blood cells is low, this is called anaemia. You may feel:

• very low in energy
• breathless 
• dizzy and light-headed. 

If you have these symptoms, contact the hospital straight away on the 24-hour number. You may need treatment for anaemia. If you are very anaemic, you may need a drip to give you extra red blood cells. This is called a blood transfusion.

Your doctor, nurse or pharmacist will prescribe anti-sickness drugs to help prevent or control sickness. Take the drugs exactly as they tell you to, even if you do not feel sick. It is easier to prevent sickness than to treat it after it has started.

If you feel sick, take small sips of fluid often and eat small amounts regularly. It is important to drink enough fluids. If you continue to feel sick, or if you are sick (vomit) 1 to 2 times in 24 hours, contact the hospital on the 24-hour number as soon as possible. They will give you advice. They may change your anti-sickness treatment. Let them know if you still feel sick.

This treatment can cause constipation. Constipation means that you are not able to pass stools (poo) as often as you normally do. It can become difficult or painful. Here are some tips that may help:

• Drink at least 2 litres (3½ pints) of fluids each day.
• Eat high-fibre foods, such as fruit, vegetables and wholemeal bread.
• Do regular gentle exercise, like going for short walks.

If you have constipation, contact the hospital on the 24-hour number for advice. They can give you drugs called laxatives to help. 

If you have not been able to pass stools for over 2 days and are being sick, contact the 24-hour number straight away. 

We want everyone affected by cancer to feel our information is written for them.

We want our information to be as clear as possible. To do this, we try to:

• use plain English
• explain medical words
• use short sentences
• use illustrations to explain text
• structure the information clearly
• make sure important points are clear.

We use gender-inclusive language and talk to our readers as ‘you’ so that everyone feels included. Where clinically necessary we use the terms ‘men’ and ‘women’ or ‘male’ and ‘female’. For example, we do so when talking about parts of the body or mentioning statistics or research about who is affected.

You can read more about how we produce our information here.