Tizanidine (tizanidine HCl)

Tizanidine hydrochloride, a centrally acting alpha2-adrenergic agonist, is a skeletal muscle relaxant.

Tizanidine hydrochloride, an imidazoline derivative, is a centrally acting alpha2-adrenergic agonist with myotonolytic effects on skeletal muscle. Tizanidine is structurally and pharmacologically related to clonidine and other alpha2-adrenergic agonists, but studies in animals indicate that tizanidine has one-tenth to one-fiftieth the potency of clonidine in lowering blood pressure. The exact mechanism of tizanidine in reducing muscle tone and spasm frequency is not clear.

However, tizanidine reportedly decreases the frequency and amplitude of muscle spasms (tonic reflexes) that arise in response to muscle stretching in patients with various spinal cord lesions. The drug appears to reduce spasticity by increasing presynaptic inhibition of motor neurons, leading to reduced facilitation of spinal motor neurons and a resultant decrease in muscle tone. Tizanidine has its greatest effects on polysynaptic pathways, with no important effect on monosynaptic spinal reflexes.

The drug does not have direct effects on skeletal muscle fibers or the neuromuscular junction. Tizanidine has been shown to have antinociceptive effects in animals, and some reports have suggested that it may improve pain associated with muscle spasm.

Tizanidine undergoes extensive first-pass hepatic metabolism. In fasting healthy individuals, peak plasma tizanidine concentrations are attained about 1 hour after administration of the commercially available capsules and tablets. The half-life of tizanidine averages about 2.5 hours.

When tizanidine is administered as two 4-mg tablets with food, the mean peak plasma concentration is increased by about 30%, the median time to peak plasma concentration is increased from about 60 to about 85 minutes, and the extent of absorption is increased by about 30%.

When tizanidine is administered as the commercially available capsules, food decreases the mean peak plasma concentration by 20%, increases the median time to peak plasma concentration from about 1 hour to 3 hours, and increases the extent of absorption by about 10%. When given with food, the amount of tizanidine absorbed from the capsule is about 80% of the amount absorbed from the tablet. Administration of the capsule contents sprinkled on applesauce is not bioequivalent to administration of the intact capsule under fasting conditions and results in a 15-20% increase in peak plasma concentration and AUC and a 15-minute decrease in median lag time and time to achieve peak plasma concentration compared with administration of intact capsules while fasting.

USES: This medication is used to treat muscle spasms caused by certain conditions (such as multiple sclerosis, spinal cord injury). It works by helping to relax the muscles.

Generic name: tizanidine HCl
Pronunciation: (tye-ZAN-i-deen)

The following indications are listed for Tizanidine:

• Muscle Spasm
• Muscle Spasticity Of Cerebral Origin
• Muscle Spasticity Of Spinal Origin

Also known as: Involuntary Muscle Contraction, Muscle Spasticity, Skeletal Muscle Spasm, Spasticity.

No ICD codes are available for this drug.