tizanidine

Therapeutic Classification: antispasticity agents (centrally acting)

Pharmacologic Classification: adrenergics

Indications ⬆ ⬇

REMS

Spasticity.

Action ⬆ ⬇

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

Therapeutic effects:

Decreased spasticity, allowing better function.

Pharmacokinetics ⬆ ⬇

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.

Time/Action Profile ⬆ ⬇

(reduced muscle tone)

ROUTE	ONSET	PEAK	DURATION
PO	unknown	1–2 hr	3–6 hr

Contraind./Precautions ⬆ ⬇

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.

Adv. Reactions/Side Effects ⬆ ⬇

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

Interactions ⬆ ⬇

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.

Route/Dosage ⬆ ⬇

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.

Availability ⬆ ⬇

(Generic available)

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

Assessment ⬆ ⬇

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.

Lab Test Considerations:

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.

Implementation ⬆ ⬇

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.

Patient/Family Teaching ⬆ ⬇

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.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

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Pronunciation ⬇

Classifications ⬆ ⬇