tizanidine hydrochloride

tizanidine hydrochloride

Zanaflex

Pharmacologic class: Alpha-adrenergic agonist (centrally acting)

Therapeutic class: Skeletal muscle relaxant

Pregnancy risk category C

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.

Route	Onset	Peak	Duration
P.O.	Unknown	1-2 hr	3-6 hr

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.