This points to needing _more_ regulation, not less. Potency could be mandated with clear warnings/notices at the point of purchase (like alcohol). The FDA (or whatever governing body) could also limit the potency.

The current status quo is that no one knows what they are getting until it's used, at which point its too late. If you could know exactly what you are getting (plus the means to seek help without fear of legal repercussions), then this would be a non-issue.

You could also have made a similar case with alcohol, but at some point the potency makes the product worse. For example, how many people do you see drinking everclear?