HEALTH : AIDS Strains May Be Resisting AZT

British pharmaceutical firm Wellcome said today that some AIDS virus strains appear to have developed resistance to its drug Retrovir--also known as AZT--the only medication licensed for treating the disease.

But Wellcome said independent experts still believe that Retrovir is an effective treatment for acquired immune deficiency syndrome. AZT, the only AIDS treatment approved by the U.S. government, has prolonged AIDS victims’ lives by up to two years. It produces severe side effects, however, such as anemia and suppression of bone marrow growth. Wellcome is also studying its use in people who have tested positive for the HIV virus but show no symptoms of AIDS.