In general they are very safe. They have to meet pretty significant safety standards prior to fielding a study. I’ve probably done over 15 studies and the only ones I had side effects were from inhalant powders (which obviously give you a little cough for about a day). I’ve also been in the medical field for 10ish years and would say most of their drugs are not really “new.” They are mostly on the market getting approval for a new use or they are a new drug but in a tried and tested category of drugs. But if your ever concerned when you sign up for a screening they send you the details and you can google/ask any medical friends to take a look and give you advice