Before the 20th century, drug safety studies were not required. 

Narcotics were sold under the counter. 

Teething babies were given serums laced with morphine. A medicine for strep was made with anti-freeze. 

No one was responsible for distinguishing between medicine that heals and medicine that harmed. 

No one studied side effects or adverse reactions. 

All you could do was roll the dice. 

Recommendations, rules, guidelines.

 Ideally, they exist to save you from unnecessary pain. Have fun and stay safe while doing it. 

But rules only work if you follow them. 

But sometimes the rules you've been following turn out to be flawed. 

All bets are off. 

You're completely on your own.