Question 72

Drowsiness

Drowsiness is a well-known side effect of diphenhydramine, a first-generation antihistamine often used for allergy relief and sleep aid. Its sedative properties are a result of its ability to cross the blood-brain barrier and block histamine receptors in the central nervous system.

A) Bradycardia

Bradycardia, which refers to a slower than normal heart rate, is not a common side effect of diphenhydramine. While some medications can affect heart rate, diphenhydramine's primary effects are related to sedation and antihistamine action rather than cardiovascular changes.

B) Hypertension

Hypertension, or high blood pressure, is not typically associated with diphenhydramine usage. In fact, diphenhydramine tends to have a calming effect rather than stimulating cardiovascular response, making this option incorrect.

C) Joint pain

Joint pain is not a recognized side effect of diphenhydramine. While some individuals may experience various side effects from medications, joint pain is not commonly linked to antihistamines like diphenhydramine.

D) Drowsiness

Drowsiness is a prevalent side effect of diphenhydramine, which is why it is often advised to avoid operating heavy machinery or driving after use. The sedative effect is a direct result of its antihistamine properties, making this option the correct answer.

Conclusion

Drowsiness is definitively the correct answer, as it is a well-documented side effect of diphenhydramine due to its antihistaminic action in the central nervous system. In contrast, the other options—bradycardia, hypertension, and joint pain—do not align with the typical pharmacological effects of diphenhydramine, confirming their incorrectness.