What is a side effect? | Cancer Research UK
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What is a side effect?

Coping with cancer

This page explains some important things about side effects of cancer drugs. There is information about


What side effects are

All drugs used to treat cancer cause side effects. Side effects are unwanted things that can happen to you as a direct result of medical treatment – in this case, taking a cancer treatment drug. It can sometimes be easy to confuse drug side effects with symptoms of the cancer. Symptoms are the things that happen to you as a direct result of the cancer and are not due to your treatment. Treatment may shrink your cancer and make your symptoms better.

Different drugs have different side effects – for example, they don't all cause hair loss or sickness. There is information about the specific side effects of many chemotherapy drugs in this section. The side effects are divided into common, occasional and rare for each drug. Ask your doctor or nurse to write down the names of your drugs so that you can look each one up.

The side effects of each drug vary for different people though. Some people find that they get only very mild side effects. You may get 1, 2 or a few side effects of a particular drug. It is not possible to say beforehand whether you will have a particular side effect, when the effect will start or stop, or how bad it will be for you. These issues depend on many factors including

  • Which drugs you are having
  • How long you have been taking the drug
  • Your general health
  • The dose (amount of drug)
  • The way you have the drug (for example, as a tablet or injection)
  • Other drugs or cancer treatments that you are having

Important things about side effects

  • Some side effects are serious medical conditions that need to be treated
  • Many side effects are inconvenient or upsetting but are not harmful to your health
  • Discuss your side effects with your doctor, nurse or pharmacist – often they can be reduced
  • Phone your cancer hospital and speak to a cancer specialist doctor or nurse urgently if you are worried about a side effect
  • Most side effects don't do any lasting harm and will gradually go away after your treatment finishes
  • If you don't get side effects, it does not mean that your treatment isn't working

Reporting side effects

A system allows doctors, nurses pharmacists and patients to report any side effects of drugs to the government's drug safety watchdog. The safety organisation is called the MHRA (the Medicines and Healthcare products Regulatory Agency). The safety system is called the Yellow Card Scheme. This scheme helps to monitor drug safety by collecting information about new or suspected side effects or drug reactions.

There is information about reporting through the Yellow Card Scheme on the MHRA website. But remember, it is important to contact your doctor if you are worried about side effects from any drugs you are taking or have recently been taking.

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Updated: 4 August 2014