Clinical Trials

Excerpt

To the editor: The limitations of randomized trials for assessing the efficacy of prophylactic therapy and efficacy in clinical practice have recently been addressed by Feinstein (1). Controlled clinical trials are even more limited in their ability to assess safety.

In assessing safety randomized trials are inherently limited by their size, duration, and failure to reflect the realities of clinical practice. For instance, a large randomized trial with 500 patients in each group has a 39% probability of seeing a side effect that occurs once in 1000 uses such as eye damage from practolol; a 5% probability of seeing a