Physiological Effects of Drugs and Alcohol
The Regulatory Baseline
Part 107 prohibits operating an sUA while under the influence of alcohol or any drug that affects the person's faculties in a manner contrary to safety. The FAA's long-standing standard for pilots is a blood alcohol concentration of 0.04 percent or higher, and the rule is "8 hours from bottle to throttle" - no alcohol within 8 hours of flight. Refusing a required test is itself a violation.
Other Substances and Conditions
Over-the-counter and prescription medications can impair judgment, reaction time, and vision. Common culprits: antihistamines, sleep aids, sedatives, and some pain medications. Illegal drugs are prohibited outright. Even legal substances can be disqualifying if they affect safety. Fatigue, stress, and illness compound impairment and are hazards in their own right.
Reporting and Responsibility
You must self-certify fitness before flight. If you have a condition or medication that could impair you, do not fly. The PIC is responsible for the crew's fitness as well - do not let an impaired observer participate.
Traps
Questions test the 0.04 percent threshold and the 8-hour rule, and whether a legal prescription drug can be disqualifying (yes, if it affects safety). Another trap: assuming the 8-hour rule alone is enough - you must also be free of impairment.
Rule of Thumb
"8 hours, 0.04, and no impairment." If you would not drive, do not fly - and if a medication warns against driving or operating machinery, treat it as grounding.