Flying ultralights is almost weirdly permissive. There is no list of approved medications which isn’t surprising–there is no medical certification even to do tandem training. FAR 103 doesn’t even mention fitness for flight.
So can I take any medication I want?
Probably not. If nothing happens it’s almost never an issue, but what if it does and you’re now facing inquiry from the FAA?
The rule they will use is 103.9(a) Hazardous operations. “No person may operate any ultralight vehicle in a manner that creates a hazard to other persons or property.” Rest assured that operating an ultralight while on drugs where you could pass out or be impaired would qualify.
What WOULD be defensible is taking the same medications allows of certified pilots. And they do have a list. It’s not a list of specific medications that you CAN take, rather it lists what they consider disqualifying for flight. An Aviation Medical Examiner (AME) would deny a medical if he found out you were on one of these medications.
States Want Some
Feds aren’t the only ones interested. States and other local law enforcement probably has laws that could be used to impart unpleasantness. And there have been cases, usually involving crashes with Alcohol.
Don’t bank on that “but we’re not an aircraft and don’t have to follow…”. Nope. Most states don’t differentiate between ultralgihts and other aircraft. If it flies and carries people, they have jurisdiction on takeoff and landing. Some states define them as “If it’s heavier than air and it flies, we regulate it.” Of course that means your kid’s paper airplane may need more scrutiny.
Yes, the FAA rules the skies, but locals rule the land (with some caveats).
“8 hours from bottle to throttle,” right?
Nope, that rule doesn’t apply. But just like for drugs, violate either that rule or blood alcohol content numbers while flying and you take a big risk. After a crash, either the state or feds may have every right to demand a test of some sorts.
Being drunk by any definition will almost certainly be considered as “creating a hazard”.