One of my mates is a director of this type of drug trial. Most of the testing is for relatively benign drugs.
Note "most". He also has a few amusing stories to tell. For some of the trials, the participants should NEVER be people who regularly operate heavy machinery in their day jobs.
A lot of these tests require the participant to remain at the hospital for up to 30 days. Typical participants are writers and musicians who need some time to "create" while being well paid to be a human guinea pig.
Birddog you should be asking this question to the people conducting the testing. Explain the requirements of your class 1 medical, as well as the DAMP requirements. If there is any doubt, then perhaps don't do it.
My 2c
DIVOSH!