Which side effect should a nurse monitor for after administering an antihistamine?

• A. Increased heart rate
• B. Constipation
• C. Excessive sweating
• D. Rash

Answer: (B)

When administering antihistamines, it is important to monitor for constipation as a common side effect. Antihistamines often have anticholinergic properties, which can lead to decreased gastrointestinal motility. This slowing of the gut can result in constipation as the normal peristaltic movements are inhibited.

While other side effects can occur with antihistamines—such as increased heart rate due to cardiovascular effects, excessive sweating because of changes in autonomic balance, or even rashes as a potential allergic reaction—constipation specifically is a well-documented and significant effect that warrants monitoring. Understanding these side effects helps healthcare providers manage patient care effectively.