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Therapeutic Classification: antispasticity agents (centrally acting)

Pharmacologic Classification: adrenergics

• Spasticity.

• Acts as an agonist at central alpha-adrenergic receptor sites.
• Reduces spasticity by increasing presynaptic inhibition of motor neurons.

• Decreased spasticity, allowing better function.

Absorption: Completely absorbed after oral administration but rapidly metabolized, resulting in 40% bioavailability.

Distribution: Widely distributed.

Metabolism/Excretion: 95% metabolized by the liver.

Half-life: 2.5 hr.

(reduced muscle tone)

Contraindicated in:

• Hypersensitivity.

Use Cautiously in:

• Renal impairment
• Hepatic impairment
• Concurrent antihypertensive therapy
• OB: Safety not established in pregnancy
• Lactation: Safety not established in breastfeeding
• Pedi: Safety and effectiveness not established in children
• Geri: Dose ↓ may be necessary in older adults due to ↓ clearance.

CV: hypotension, bradycardia.

Derm: rash, skin ulcers, sweating.

EENT: blurred vision, pharyngitis, rhinitis.

GI: abdominal pain, diarrhea, dry mouth, dyspepsia, constipation, ↑ liver enzymes, vomiting.

GU: urinary frequency.

MS: back pain, myasthenia.

Neuro: anxiety, depression, dizziness, paresthesia, sedation, weakness, dyskinesia, hallucinations, nervousness, speech disorder.
Misc: fever.

Drug-Drug:

• Levels and effects ↑ by concurrent use of hormonal contraceptives or alcohol.
• ↑risk of hypotension with alpha₂-adrenergic agonist antihypertensives; avoid concurrent use.
• ↑CNS depression may occur with alcohol or other CNS depressants, including some antidepressants, sedative/hypnotics, antihistamines, and opioid analgesics.
• CYP1A2 inhibitors, including ciprofloxacin and fluvoxamine, may ↑ levels and risk of hypotension and excessive sedation.

Tablets are not interchangeable with capsules

• PO (Adults): 4 mg every 6–8 hr initially (no more than 3 doses/24 hr); ↑ by 2–4 mg/dose up to 8 mg/dose or 24 mg/day (not to exceed 36 mg/day). Some patients may tolerate twice-daily dosing.

(Generic available)

• Tablets: 2 mg; 4 mg;
• Capsules: 2 mg; 4 mg; 6 mg;

• Assess muscle spasticity before and periodically during therapy.
  • Monitor BP and pulse, especially during dose titration. May cause orthostatic hypotension, bradycardia, dizziness, and, rarely, syncope. Effects are usually dose related.
  • Observe patient for drowsiness, dizziness, and asthenia. A change in dose may alleviate these problems.

• Monitor liver function tests before and at 1, 3, and 6 mo of therapy. May cause ↑ in serum glucose, alkaline phosphatase, AST, and ALT levels.

• Do not confuse tizanidine with nizatidine or tiagabine.
  • Doses should be titrated carefully to prevent side effects.
• PO: May be taken without regard to meals.

• Instruct patient to take tizanidine as directed. Tizanidine may need to be discontinued gradually.
• May cause dizziness and drowsiness. Advise patient to avoid driving or other activities requiring alertness until response to drug is known.
• Instruct patient to change positions slowly to minimize orthostatic hypotension.
• Advise patient to avoid concurrent use of alcohol or other CNS depressants while taking this medication.
• Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

• Decrease in muscle spasticity with an increased ability to perform activities of daily living.

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