People with blood related cancers such as leukaemia, lymphoma or myeloma are at risk of developing gout. This is a condition that causes painful swelling in joints such as the big toe, ankle or knee. Taking allopurinol helps to prevent gout developing. The risk of gout is especially high when people first start their treatment. So, allopurinol is often prescribed when treatment is due to begin.

Gout is caused by a chemical called uric acid building up in the body. The uric acid collects in the blood and forms stones in the kidney, the joints and in the cartilage of the ear.

When cells die, they are broken down in the body and make uric acid as a waste product. Normally we clear the uric acid out of our bodies in our urine. But, if you have a leukaemia, lymphoma or myeloma you may have a higher level of uric acid in your blood. This is because your bone marrow is making lots of abnormal cells and as some die and are broken down uric acid is released.

The already high level of uric acid can sometimes increase greatly when you have chemotherapy. This is because many cancer cells will be killed very rapidly by the chemotherapy drugs and release a lot of uric acid into the body. Having very high levels of uric acid can cause serious problems, especially for your kidneys. If not treated it could even lead to kidney failure.

Taking allopurinol is an important way of preventing this problem. Allopurinol stops the body making uric acid and makes it easier for your body to wash out waste products from cell breakdown in the urine.

Allopurinol is taken as a tablet, by mouth. It is a very safe drug with few side effects. And, it is unlikely that you will have any problems with it. But, a small number of people develop an allergic reaction to allopurinol. This usually shows up as an itchy skin rash. So, if you notice a rash or any other changes when you start taking it let your doctor know straight away.