SkyDrill

Diphenhydramine side effects

Remote Pilot (Part 107) practice question 18 of 20 on Operations / Physiology. ACS element UA.V.E.K3 · difficulty: recall. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONAccording to the Remote Pilot Study Guide, why are medications containing diphenhydramine a particular concern for pilots?

  1. AThey raise blood pressure and shorten reaction time only briefly
  2. BThey cause drowsiness and have a prolonged half-life
  3. CThey sharpen alertness but reduce peripheral vision
Show the answer and explanation

Correct answer: B. They cause drowsiness and have a prolonged half-life

  • A — incorrect The study guide does not describe diphenhydramine this way; its concern is drowsiness that lasts a long time because of the drug's prolonged half-life.
  • B — correct The study guide singles out medications containing diphenhydramine as known to cause drowsiness and to have a prolonged half-life, meaning they stay in the system for an extended time and lengthen the period of side effects.
  • C — incorrect Diphenhydramine causes drowsiness rather than sharpening alertness, and the study guide does not associate it with peripheral vision loss.

BACKGROUND

The Remote Pilot Study Guide notes that some of the most commonly used over-the-counter (OTC) drugs, antihistamines and decongestants, can cause noticeable adverse side effects including drowsiness and cognitive deficits. Cold symptoms often suppress a pilot's desire to fly, and treating them with a drug that has side effects only compounds the problem. Medications containing diphenhydramine are specifically called out because they cause drowsiness and have a prolonged half-life, so they remain in the body for an extended time and lengthen the period during which side effects are present.

STUDY TIP

Associate diphenhydramine with two words: drowsiness and prolonged half-life.

KEY POINTS

  • Antihistamines and decongestants can cause drowsiness and cognitive deficits.
  • Diphenhydramine products cause drowsiness and have a prolonged half-life.
  • Side effects last longer because the drug stays in the system longer.

SOURCES

  • remote_pilot_study_guide.txt ch9 "Drugs"
Practice the Remote Pilot (Part 107) test →Timed 60-question exam, by ACS area, or review your misses. Free.
MORE ON OPERATIONS / PHYSIOLOGY

SkyDrill is not affiliated with the FAA. This is an original practice item based on 14 CFR part 107, 14 CFR part 89, and the FAA Remote Pilot – Small UAS Study Guide (FAA-G-8082-22). Regulations and handbooks are revised; confirm details against the current edition.