Many drugs work by “fixing” a particular biological pathway that’s gone awry in a disease. But sometimes drugs affect other pathways too, producing undesirable side effects that can be severe enough to outweigh the drug’s benefits. Such is the case for the thiazolidinedione drugs (also known as TZDs), which are used to treat type 2 diabetes. These are highly effective in controlling blood glucose levels and have an added benefit of lowering blood pressure in some patients. However, TZDs cause unrelated but potentially severe side effects in some patients, including heart failure, bone fracture, and to a lesser degree heart attack or bladder cancer depending on the specific TZD. The actual risks vary depending upon a patient’s specific circumstances. Nonetheless, because of increased recognition of these unwanted effects, the rate of new TZD prescriptions is on the decline.
