Zanaflex, or tizanidine, is a prescription muscle relaxant drug used to treat muscle spasms and tightness. It is intended for short-term use because its effects are not long lasting. As tightness decreases and the muscles begin to relax, then temporary relief of muscle pain and discomfort can be experienced. This drug functions by blocking the pain signals from the spinal cord to the brain. This medication should not be taken in concert with fluvoxamine, an antidepressant, or with the antibiotic known as ciprofloxacin.
Allergic Effects
An allergic reaction is possible with any medication, including Zanaflex, and can be a life-threatening situation. Get emergency assistance immediately if any or a combination of the following signs appear that are indicative of an allergic reaction: a rash or hives; severe shortness of breath or labored difficulty in breathing; swelling about the face, which may involve the lips or tongue; and, severe dizziness, fainting or lightheadedness and sweating.
Heart and Kidneys
Serious yet rare side effects that can be produced by this drug are a slow or irregular heartbeat as well as a long QT cardiac syndrome; additionally, high or low blood pressure may result (hypertension and hypotension). Any history of kidney disease prior to beginning this drug should be made clear to the prescribing physician as well as back pain, frequent urination, dark urine or pain while urinating after starting this medication. This drug has been associated with possible urinary tract infections or flu-like symptoms as well as a low-grade fever.
Gastrointestinal and Liver
Serious side effects can occur to gastrointestinal and hepatic-biliary systems. For example, a loss in appetite as well as continuing (persistent) nausea and vomiting, indigestion or stomach pain may be experienced after starting Zanaflex. Also, clay-colored or black stools with weakness and fatigue, constipation or diarrhea may present. The onset of unusual bleeding or bruising, especially with the presence of tarry stools should be noted. There may be signs of liver damage or dysfunction such as jaundice, that is, yellowing of the skin or eyes. A doctor should be contacted if any of or a combination of these side effects present.
Other Effects
Other side effects are possible with this drug. Drowsiness, numbness and tingling as well as speech, hearing or vision problems have been reported. Additionally, rare occurrences of confusion, mood changes including anxiety or nervousness and depression have been reported. The rare side effects of hallucinations and unusual behaviors may be experienced.
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