Anticholinergics are drugs that block the action of acetylcholine. Acetylcholine is a neurotransmitter, or a chemical messenger. Anticholinergics include atropine, dicyclomine, diphenoxylate, glycopyrrolate, hyoscyamine, ipratropium, oxybutynin, propantheline, tolterodine, and trihexyphenidyl. Uses, dosages, and side effects of all these drugs are also discussed in this chapter. Common side effects are dry mouth, constipation, drowsiness, dizziness, nausea, blurred vision, dry eyes, disturbed urinary voiding pattern, tachycardia, and decreased sweating.