I would say that most drugs have different effects at different doses.
It's usually not the drug that is the problems, it's the dosage.
To answer the rapamycin question: the normal dose that is given in case of an organ transplant is 6mg on day one and after that 2mg per day. That makes for 14-18mg/week.
For longevity what I've heard is 3-5mg once per week.
Now take your normal OTC drug, let's say Tylenol and take 3-4 times the recommended dose. Liver injury or even liver failure follows.
To answer the rapamycin question: the normal dose that is given in case of an organ transplant is 6mg on day one and after that 2mg per day. That makes for 14-18mg/week. For longevity what I've heard is 3-5mg once per week.
Now take your normal OTC drug, let's say Tylenol and take 3-4 times the recommended dose. Liver injury or even liver failure follows.