The nurse is advising a client who been using diphenhydramine (Benadryl) over-the-counter (OTC) to induce sleep. The client complains about a dry mouth. The nurse explains that:

Question

1. Diphenhydramine causes less dryness if taken in the liquid form.
2. Drying of the mouth membranes is common after taking diphenhydramine.
3. Drowsiness caused by the diphenhydramine caused the client to reduce fluid intake.
4. Diphenhydramine has a muscle relaxant effect, so the client is likely sleeping with the mouth open.

Answer 1

Correct Answer: 2
Rationale 1: Substituting the liquid form for another form will not make any difference.
Rationale 2: Diphenhydramine is an antihistamine with a potent anticholinergic effect that promotes dry mouth.
Rationale 3: Diphenhydramine does not reduce fluid intake in a significant way.
Rationale 4: The client might sleep with the mouth open, but that is not the primary cause of the dry mouth.
Global Rationale: The major adverse effect of antihistamines relates to their anticholinergic effects. Excessive drying of mucous membranes can lead to dry mouth, and urinary hesitancy may be troublesome for patients, especially those with prostatic hyperplasia. Some antihistamines produce more pronounced anticholinergic effects than others. Diphenhydramine and clemastine exhibit a significant incidence of anticholinergic adverse effects, whereas the second-generation agents—loratadine, desloratadine, and fexofenadine—produce the least. Substituting the liquid form for another form will not make any difference. Diphenhydramine does not reduce fluid intake in a significant way. The client might sleep with the mouth open, but that is not the primary cause of the dry mouth.