Pharmacological and Parenteral TherapiesQuestion 1724 of 2368
A client takes diphenhydramine for allergy symptoms and reports drowsiness. Which mechanism best explains this effect?
- The drug is blocked from the brain and builds up in the blood
- The drug increases the liver's production of sedating enzymes
- The drug is excreted too slowly by the lungs and the skin
- The drug crosses the blood-brain barrier and depresses the CNS
Show answer
Correct answer: The drug crosses the blood-brain barrier and depresses the CNS
Diphenhydramine can cross the blood-brain barrier and depress the central nervous system, causing drowsiness as a side effect.
Source: Nursing Pharmacology, 2nd edition (Open RN, Chippewa Valley Technical College, 2023), Pharmacokinetics & Pharmacodynamics: Blood-Brain Barrier. Licensed under CC BY 4.0.
Practice the topic "Pharmacological and Parenteral Therapies"Questions last reviewed: 18 October 2026