Certification of Pharmacy Technicians (ExCPT) Practice Exam

Which of the following is a common side effect of antihistamines?

1. A. Diarrhea

2. B. Drowsiness

3. C. Insomnia

4. D. Weight loss

The correct answer is: B. Drowsiness

Drowsiness is a well-known side effect of antihistamines, particularly first-generation antihistamines. These medications, which include diphenhydramine and chlorpheniramine, cross the blood-brain barrier and block histamine receptors in the central nervous system, leading to sedative effects. This is often utilized in products meant to aid sleep or relieve allergy symptoms that may disrupt sleep, but can be a cause for concern when driving or operating machinery. Other alternatives such as diarrhea, insomnia, and weight loss are not typically associated with antihistamines. While some antihistamines may have varying side effects, drowsiness remains the hallmark effect that patients and healthcare providers must monitor for, especially in populations such as the elderly or those who are on multiple medications. Understanding this side effect is crucial for safe and effective patient care, particularly in managing allergies while avoiding complications related to sedation.