Side effects and cautions

These medications can have strong side effects, so they aren't commonly used. Side effects include:

• Fatigue
• Drowsiness or sedation
• Dizziness
• Impotence
• Constipation
• Abnormally slow heart rate
• Dry mouth
• Headache
• Fever

Abruptly stopping use of some central-acting agents can cause a sudden, dangerous increase in blood pressure. Don't stop taking these medications without talking to your doctor.