tizanidine hydrochloride

Action

Stimulates alpha₂-adrenergic agonist receptor sites and reduces spasticity by inhibiting presynaptic motor neurons

Availability

Tablets: 2 mg, 4 mg

Indications and dosages

➣ Increased muscle tone associated with spasticity

Adults: Initially, 4 mg P.O. q 6 to 8 hours (no more than three doses in 24 hours). Increase in increments of 2 to 4 mg, up to 8 mg/dose or 24 mg/day (not to exceed 36 mg/day), as needed.

Contraindications

• Hypersensitivity to drug or its components

Precautions

Use cautiously in:

• renal or hepatic impairment

• elderly patients

• pregnant or breastfeeding patients

• children (safety not established).

Administration

• Give with or without food.

Adverse reactions

CNS: drowsiness, asthenia, dizziness, speech disorder, dyskinesia, nervousness, anxiety, depression, hallucinations, sedation, paresthesia

CV: hypotension, bradycardia

EENT: blurred vision, pharyngitis, rhinitis

GI: vomiting, diarrhea, constipation, abdominal pain, dyspepsia, dry mouth

GU: urinary frequency, urinary tract infection

Hepatic: hepatitis

Musculoskeletal: back pain, myasthenia

Skin: rash, skin ulcers, sweating

Other: fever, infection, flulike symptoms

Interactions

Drug-drug. Alpha₂-adrenergic agonist antihypertensives: increased risk of hypotension

CNS depressants (such as antihistamines, opioids, sedative-hypnotics): additive CNS depression

Hormonal contraceptives: increased tizanidine blood level, greater risk of adverse reactions

Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, glucose: increased levels

Drug-food. Any food: increased drug bioavailability, shorter time to peak concentration (with no effect on absorption)

Drug-behaviors. Alcohol use: additive CNS depression

Patient monitoring

• Monitor temperature and vital signs. Watch for orthostatic hypotension, bradycardia, and fever or other signs and symptoms of infection.

• Assess liver function tests.

Patient teaching

• Advise patient he may take with or without food.

• Tell patient to report signs or symptoms of infection or depression.

• Instruct patient to move slowly when sitting up or standing, to avoid dizziness from sudden blood pressure decrease.

Tell patient to immediately report unusual tiredness or yellowing of skin or eyes.

• Caution patient not to drink alcohol.

• Instruct patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, foods, and behaviors mentioned above.