By DR. FIONA CHAN, NEUROLOGY ADVANCED TRAINEE:
Azathioprine was first produced in the 1950’s and since then has been used for a variety of disorders related to our immune process. It comes as a tablet to take by mouth and has to be taken consistently. This medication works by inhibiting DNA and RNA synthesis which are building blocks for the formation of lymphocytes. (Lymphocytes are the immune cells responsible for producing antibodies). Hence, this medication is slow to take effect as it targets the ‘factories’ responsible for producing the antibodies rather than targeting the antibodies directly. Its full clinical benefits often take 6 months to 1 year to become apparent.
The most common side effects are nausea and vomiting. Your doctor should also be monitoring certain blood counts regularly to ensure other side effects such as a reduction in your red and white blood cells are recognised early to ensure your Azathioprine doses can be adjusted accordingly.
LEARNING BITE (by Dr Fiona Chan)
It is unique though in the aspect of its interaction with Allopurinol (a medication commonly used to treat gout). This is because the body is reliant on an enzyme (xanthine oxidase) to metabolise and remove Azathioprine from the body, however, allopurinol blocks this specific enzyme pathway. This is the reason why you should let your doctor know if you are prescribed both allopurinol and azathioprine. However, there are certain occasions where doctors will knowingly prescribe both of these medications for a synergistic or beneficial clinical effect in a certain group of patients. The key is to make sure that the prescribing doctor is aware you are on any of these medications and if prescribed either allopurinol or azathioprine.