Dry mouth, drowsiness, dizziness, lightheadedness, constipation, weakness, and tiredness may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. To relieve dry mouth, suck (sugarless) hard candy or ice chips, chew (sugarless) gum, drink water, or use a saliva substitute. To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if you have any serious side effects, including: fainting, mental/mood changes (such as hallucinations), slow/irregular heartbeat, vision changes (such as blurred vision). Tizanidine has rarely caused very serious (rarely fatal) liver disease. Tell your doctor right away if you develop symptoms of liver disease, including: persistent nausea/vomiting, severe stomach/abdominal pain, dark urine, yellowing eyes/skin. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.