Side effects may vary among these medications, and most of them lessen as the person continues to take the medication. Side effects include:

• Stomach upset and other problems, such as constipation.
• Dry mouth, blurred vision, and drowsiness.
• Lowered blood pressure.
• Weight gain.
• Tremors and sweating.
• Inability to urinate (urinary retention).
• Loss of sexual desire or ability.
• Confusion or delirium in older adults.

The most important side effects include cardiac problems in those with previous heart disease. They may be fatal in overdose.