The DEA has a system in place which allows doctors and other people , such as dentists , physician assistants , and nurse practitioners , to prescribe medicines , researchers and manufacturers access to `` Schedule I '' drugs , as well as Schedules 2 , 3 , 4 and 5 . The DEA has a registration system in place which authorizes medical professionals , researchers and manufacturers access to `` Schedule I '' drugs , as well as Schedules 2 , 3 , 4 and 5 .