A nervous 57-year-old woman with a fear of injections receives a premedication in the waiting area and, 45 minutes later, presents with dry mouth and a heart rate of 45 bpm. Which premedication is most likely responsible for these symptoms?

A nervous 57-year-old woman with a fear of injections receives a premedication in the waiting area and, 45 minutes later, presents with dry mouth and a heart rate of 45 bpm. Which premedication is most likely responsible for these symptoms?

• A. Scopolamine
• B. Meperidine
• C. Midazolam
• D. Clonidine

Answer: (D)

Clonidine acts by stimulating central alpha-2 receptors, which dampens sympathetic outflow. That lowers heart rate and blood pressure and also reduces salivary secretions, producing dry mouth. The timing fits too—oral premedication can cause effects within about 30–60 minutes, so a bradycardic rate of 45 bpm with dry mouth about 45 minutes after administration is classic for clonidine. The other medications have different profiles. Scopolamine causes dry mouth but tends to raise heart rate due to anticholinergic effects. Meperidine can cause bradycardia via opioid effects but doesn’t typically cause prominent dry mouth as a defining feature. Midazolam can cause mild bradycardia but is not associated with significant dry mouth.

Clonidine acts by stimulating central alpha-2 receptors, which dampens sympathetic outflow. That lowers heart rate and blood pressure and also reduces salivary secretions, producing dry mouth. The timing fits too—oral premedication can cause effects within about 30–60 minutes, so a bradycardic rate of 45 bpm with dry mouth about 45 minutes after administration is classic for clonidine.

The other medications have different profiles. Scopolamine causes dry mouth but tends to raise heart rate due to anticholinergic effects. Meperidine can cause bradycardia via opioid effects but doesn’t typically cause prominent dry mouth as a defining feature. Midazolam can cause mild bradycardia but is not associated with significant dry mouth.