Tizanidine is a medication that is used to control muscle spasms, as well as alleviate the pain commonly associated with them. It operates by stimulating certain cells in the body containing alpha-adrenergic receptors. Many of the potential tizanidine side effects that can occur from taking this medication are related to the stimulation of these receptors, either in muscle tissue or other types of cells.
Generally, the more common tizanidine side effects are also the least harmful. Dry mouth, dizziness, fatigue, and constipation may all result from taking this medication. Most patients tolerate this drug fairly well, and even these common side effects do not occur in the majority of people taking it.
Other tizanidine side effects that involve either the gastrointestinal (GI) tract or muscles are also quite common. Nausea, GI discomfort, and stomach pain occur in a substantial minority of individuals taking this medication. Back pain may occur from increased muscle tension, and increased back spasms may temporarily occur. These side effects are usually mild, and they tend to go away after several days of taking tizanidine.
Some tizanidine side effects are considered more rare than those already listed, but still occur frequently enough to be mentioned in the manufacturer's warnings. Adverse affects in this category include vomiting, sweating, and rash. A numb sensation or tingling may occasionally be felt in the limbs, as well.
Less common tizanidine side effects have a tendency to be more severe, as well. Usually, they call for immediate medical attention, since they can signify a harmful reaction to the medication. Fainting, blurred vision, or mood changes may all indicate effects on the central nervous system that are uncommon, and could be dangerous. Difficulty urinating, or painful urination may also be indicative of more serious problems.
Allergic reactions to tizanidine are uncommon, but can be life-threatening, which is why they require medical attention. The most common signs of allergies to this drug include swelling, difficulty breathing, and dizziness. Itching or a rash may also break out on the skin, as well.
In very rare cases, the heart rate may be affected by tizanidine, resulting in irregular beats. Severe GI problems may rarely occur as well, causing severe stomach pain, and black or bloody stool. These symptoms necessitate immediate attention in order to be treated before life-threatening complications can rise. Left untreated, the underlying conditions causing these symptoms have the potential to quickly become fatal.