👉 Azathioprine is a medication used to treat certain types of blood cancer. It works by blocking a protein called Bruton's tyrosine kinase (BTK), which can help prevent or stop the growth and spread of blood cancers. Azathioprine is usually prescribed as a pill, but it may also be given as a liquid solution for oral administration. This medication helps to reduce the amount of cancer cells in your body while also helping to slow down their ability to divide and grow.