Call 911 would definitely be the first step followed by, administer chest compressions. If chest compressions do not work and the person becomes unconscious you then lower the person to the ground and try to clear the airway. Finally you perform rescue breathes, and if the chest does not visibly rise that is when you begin to preform CPR until rescue vehicles arrive.
It would be drug interactions because if they act differently when they are taken together than they do alone then they are mixing and causing an interact
