A nurse is teaching a client about taking diphenhydramine. The nurse should explain to the client that which of the following is an adverse effect of this medication?
A.
Headache
B.
Constipation
C.
Bradycardia
D.
Hypertension
The Correct answer and Explanation is: The correct answer is B. Constipation.
Explanation:
Diphenhydramine, commonly known by its brand name Benadryl, is an antihistamine often used to relieve symptoms of allergy, hay fever, and the common cold. It works by blocking histamine, a substance in the body that causes allergic symptoms. While effective for these purposes, diphenhydramine has a range of side effects, primarily due to its anticholinergic properties. Understanding these side effects is critical, especially for clients who are using this medication regularly or in high doses.
Constipation is a significant adverse effect of diphenhydramine. This occurs because diphenhydramine exhibits strong anticholinergic activity, meaning it inhibits the action of the neurotransmitter acetylcholine. Acetylcholine is crucial for the normal functioning of the parasympathetic nervous system, which is responsible for stimulating bowel movements. When acetylcholine action is inhibited, as it is with diphenhydramine, smooth muscle activity in the gastrointestinal tract is reduced, leading to slower bowel motility and, consequently, constipation. Patients, especially older adults, are at a higher risk of experiencing this side effect and may need to take preventive measures, such as increasing fiber intake or using stool softeners.
Other common anticholinergic side effects of diphenhydramine include dry mouth, urinary retention, blurred vision, and drowsiness. These effects are a result of the same mechanism—blocking acetylcholine. Given the sedative properties of diphenhydramine, it can also cause significant drowsiness, which is why it is sometimes used as a sleep aid. However, it is essential for the nurse to educate the client about the potential for these adverse effects, particularly constipation, and to advise on ways to manage them.
The other options are not typically associated with diphenhydramine:
- Headache (Option A) is not a common adverse effect.
- Bradycardia (Option C), or slow heart rate, is not expected; if anything, tachycardia (fast heart rate) could be seen in some cases due to the anticholinergic effects.
- Hypertension (Option D) is also not a typical adverse effect; in fact, diphenhydramine can sometimes cause hypotension, especially in elderly patients.
In conclusion, nurses should be vigilant in educating patients about the potential for constipation when taking diphenhydramine and encourage appropriate lifestyle modifications to mitigate this side effect.