Zanaflex (Tizanidine-Oral (tize-AN-ih-deen))

Zanaflex is a muscle relaxant is used to help relax certain muscles in your body. It relieves the spasms and increased muscle tone caused by medical problems such as multiple sclerosis or spinal injury. This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Tizanidine is an agonist at (alpha) 2 -adrenergic receptor sites and presumably reduces spasticity by increasing presynaptic inhibition of motor neurons. In animal models, tizanidine has no direct effect on skeletal muscle fibers or the neuromuscular junction, and no major effect on monosynaptic spinal reflexes. The effects of tizanidine are greatest on polysynaptic pathways. The overall effect of these actions is thought to reduce facilitation of spinal motor neurons.

The imidazoline chemical structure of tizanidine is related to that of the anti-hypertensive drug clonidine and other (alpha) 2 -adrenergic agonists. Pharmacological studies in animals show similarities between the two compounds, but tizanidine was found to have one-tenth to one-fiftieth (1/50) of the potency of clonidine in lowering blood pressure.

Before taking this medication, tell your doctor if you have liver disease, have kidney disease, have low blood pressure or you are on medication to treat high blood pressure; or you are taking birth control pills. You may not be able to take Zanaflex, or you may require a lower dose or special monitoring during treatment if you have any of the conditions listed above. Do not take this medication without first talking to your doctor if you are pregnant. It is not known whether Zanaflex passes into breast milk. Do not take Zanaflex without first talking to your doctor if you are breast-feeding a baby.

Side effects from Zanaflex can occur. Tell your doctor if any of these symptoms are severe or do not go away: dizziness, upset stomach, vomiting, tingling sensation in the arms, legs, hands, and feet, dry mouth, increased muscle spasms. If you experience either of the following symptoms, call your doctor immediately: yellowing of the skin or eyes, unexplained flu-like symptoms.

• If you experience any of the following serious side effects, stop taking tizanidine and seek emergency medical attention:
  • an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);
  • hallucinations or abnormal behavior; or
  • liver damage (yellowing of the skin or eyes, nausea, abdominal pain or discomfort, unusual bleeding or bruising, severe fatigue).
• Other, less serious side effects may be more likely to occur. Continue to take tizanidine and talk to your doctor if you experience
  • drowsiness or dizziness;
  • weakness;
  • dry mouth;
  • increased muscle tone or spasms; or
  • sweating.
• Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.