Hi, Thanks for posting in HCM. I understand your concern. Azathioprine is an immunosuppressant drug used in organ transplantation and autoimmune diseases. It belongs to the chemical class of purine analogues. Common side effects encountered with the use of the drug include: Black stools, bleeding gums, blood in the urine, chest pain, cough or hoarseness of voice, fever, lower backache, difficulty in urination, pinpoint red spots on the skin, shortness of breath, sore throat, sores, ulcers, or white spots on the lips or in the mouth, swollen glands, unusual bleeding or bruising and unusual tiredness or weakness. Kindly consult your doctor to review the dose in case the side effects experienced are bothering you much and cannot be tolerated. Hope the information provided would be helpful. All the best.