Azathioprine is a generic version of AAIPharma LLC's Azasan drug, used to prevent a patient's body from rejecting a transplanted kidney. Azathioprine is also used to treat symptoms of rheumatoid arthritis. Alkem's azathioprine drug will be available in 25-mg, 50-mg, 75-mg, and 100-mg strengths. At 0935 IST, shares of the drug maker were up nearly 1% at 2,345.20 rupees on the National Stock Exchange.