Azathioprine 50mg Tablet works by weakening the body’s immune system, so it does not attack the new organ. The amount of medicine to be taken and how often you need to take it will depend on the type of transplant you have. Follow your doctor’s instructions on this. You should take it along with food. Take the medicine regularly to get the most benefit and keep taking it even if you feel well. If you stop taking it, you may increase the chances of rejecting your transplanted organ.