Do not take your dose twice. However, it may take up to 3 weeks before you feel the full effect. The most common side effects are dizziness, drowsiness, lightheadedness, confusion, agitation, increased anxiety, etc. To relieve dry mouth, suck on (sugarless) hard candy or ice chips, chew (sugarless) gum, drink water, or use a saliva substitute. Consult your doctor concerning proper dose for you.