It’s not possible to do clinical trials on every scenario. Naltrexone, for example, is an opioid blocker in high doses, but acts as an anti-inflammatory in low doses. Low dose naltrexone is an off-label use that isn’t FDA approved, but it’s been used for over a decade and continues to be used based on results achieved in clinical practice.

Anecdotal evidence has its value. Observation is an important part of the scientific method. Sure, it would be great if there were time and resources to research everything first, but it’s not. And there have been plenty of drugs declared safe after clinical trials, only to find out later they weren’t like Vioxx and Oxycontin.