Tizanidine Hydrochloride	(tye-ZAN-i-deen HYE-droe-KLOR-ide)FDA MEDWATCH ALERT
Trade Name(s):	Tizanidine Hydrochloride   ·Tablets 2 mg   ·Tablets 4 mg   Zanaflex   ·Tablets 2 mg   ·Tablets 4 mg   ·Capsules 2 mg   ·Capsules 4 mg   ·Capsules 6 mg Apo-Tizanidine Gen-Tizanidine Indicates Canadian Trade Name.
Class:	Skeletal muscle relaxant
Action:	An alpha-2 adrenergic receptor agonist that may reduce spasticity by increasing presynaptic inhibition of motor neurons. Absorption: Well absorbed; absolute bioavailability is about 40% because of extensive first-pass hepatic metabolism. T max is 1 h (tablets and capsules in fasted state); food increases T max (1 h and 25 min for tablets; 3 to 4 h for capsules); food increases C max of tablets 30% and reduces C max of capsules 20%. Administration of capsule contents sprinkled on applesauce increases C max and AUC 15% to 20% and decreases T max 15 min compared with administration of intact capsule.
	Distribution: Tizanidine is widely distributed. Vd is about 2.4 L/kg. About 30% is bound to plasma proteins.
	Metabolism: About 95% of dose is metabolized (CYP1A2); metabolites are not known to be active.
	Excretion: The half-life is about 2 to 2.5 h.
	Peak: 1 to 2 h.
	Duration: 3 to 6 h.
	Special Populations: Renal Function Impairment - Cl is reduced more than 50% in elderly patients with renal function impairment (CrCl less than 25 mL/min) compared with healthy subjects; this may lead to longer duration of clinical effects. Hepatic Function Impairment - Effect of hepatic impairment on the pharmacokinetics have not been evaluated. Avoid or use with extreme caution. Elderly - Younger subjects cleared drug 4 times faster than elderly subjects. Gender - Effect of gender on the pharmacokinetics have not been evaluated. Race - Effect of race on the pharmacokinetics have not been evaluated.
Indications:	Acute and intermittent management of increased muscle tone associated with spasticity.
Contraindications:	Coadministration of ciprofloxacin or fluvoxamine; hypersensitivity to any component of the product.
Interactions:
	ACE inhibitors (eg, lisinopril) Pharmacologic effects of ACE inhibitors may be increased, possibly resulting in severe hypotension.
	Acetaminophen The time to reach acetaminophen peak concentrations may be delayed.
	Alcohol Plasma levels of tizanidine may be elevated, increasing the adverse reactions.
	Antihypertensive agents Use with caution; do not administer with other alpha-2 adrenergic agonists (eg, clonidine).
	Ciprofloxacin, fluvoxamine Coadministration with tizanidine is contraindicated. Tizanidine plasma concentrations may be elevated, increasing the risk of adverse reactions (eg, hypotension, sedation).
	CYP1A2 inhibitors (eg, acyclovir, antiarrhythmic agents [eg, amiodarone, mexiletine, propafenone, verapamil], cimetidine, famotidine, fluoxetine, hormonal contraceptives, quinolone antibiotics [eg, norfloxacin], ticlopidine, zileuton) Tizanidine plasma levels may be elevated, increasing pharmacologic effects and adverse reactions.
Lab Test Interferences:	None well documented.
Adverse Reactions:
	cardiovascular: Hypotension (33%); bradycardia (10%).
	cns: Somnolence (92%); asthenia (78%); dizziness (45%); dyskinesia, nervousness, speech disorder (3%); anxiety, depression, paresthesia (at least 1%).
	dermatologic: Rash, skin ulcer, sweating (at least 1%).
	eent: Amblyopia, pharyngitis, rhinitis (3%).
	gi: Dry mouth (88%); constipation (4%); vomiting (3%); abdomen pain, diarrhea, dyspepsia (at least 1%).
	gu: UTI (10%); urinary frequency (3%).
	labtestabs: Abnormal LFTs (3%).
	musculoskeletal: Back pain, myasthenia (at least 1%).
	miscellaneous: Infection (6%); flu syndrome (3%); fever (at least 1%).
Precautions:
	Monitoring: Monitor transaminase levels before starting therapy, during the first 6 mo (eg, 1, 3, 6 mo), and periodically thereafter during long-term therapy. Monitor patients with CrCl less than 25 mL/min for onset or increase in severity of common adverse reactions (eg, dry mouth, dizziness, somnolence).
	Pregnancy: Category C .
	Lactation: Undetermined.
	Children: Safety and efficacy not established.
	Elderly: Use with caution because Cl may be decreased 4-fold.
	Renal function impairment: Use with caution in patients with renal function impairment (CrCl less than 25 mL/min). Reduce dose during initial titration; if higher doses are required, increase individual doses rather than dosing frequency. Closely monitor for onset or increase in severity of common adverse reactions (eg, asthenia, dizziness, dry mouth, somnolence).
	Hepatic function impairment: Avoid or use with caution.
	Hazardous tasks: Dose-related sedation, interfering with daily activities, commonly occurs. Drowsiness may be noted within 0.5 h of dosing and peaks at 1.5 h following dose.
	Bioequivalence Tablets and capsules are bioequivalent to each other under fasted conditions, but not under fed conditions.
	CV Reduced pulse rate and BP may occur.
	Chronic use Clinical experience with long-term use of single doses of tizanidine at 8 to 16 mg or total daily doses of 24 to 36 mg is limited.
	Discontinuation of treatment Decrease dose slowly to minimize risk of withdrawal, rebound hypertension, tachycardia, and hypertonia, especially in patients who have received high doses for prolonged periods.
	Hallucinosis/Psychotic-like symptoms Hallucinations, delusions, and psychosis in association with hallucinations may occur.
	Hepatic toxicity Hepatocellular liver injury may occur.
	Hypotension Dose-related hypotension may occur, starting within 1 h of administration and peaking 2 to 3 h after administration. Bradycardia, light-headedness/dizziness, orthostatic hypotension, and syncope (rarely) have been reported.
	Posture/balance/function Use with caution when spasticity is utilized to sustain posture, balance in locomotion, or increased function.
Overdosage:	Signs & symptoms Bradycardia, confusion, coma, depressed cardiac function, hypotension, lethargy, respiratory depression, somnolence.
Patient/Family Education:	Advise patient that there is limited experience with tizanidine in regard to duration of use and the higher doses required to reduce muscle tone. Advise patient to review the patient information leaflet carefully before starting therapy, and to read and check for new information each time the medication is refilled. Review dosing schedule with patient. Advise patient that medication is started at a low dose and gradually increased as tolerated until max benefit is achieved. Instruct patient to take prescribed dose at 6? to 8?h intervals as needed for spasticity, to a max of 3 doses in a 24?h period. Advise patient to take tizanidine consistently with or without food. Caution patient not to change from tablets to capsules, or from capsules to tablets, without discussing with health care provider because dosing changes may be required. Advise patient that if medication needs to be discontinued, it will be slowly withdrawn unless safety concerns (eg, rash) require a more rapid withdrawal. Caution patient not to stop taking the medication abruptly or decrease the dose unless advised by health care provider because of risk of developing withdrawal symptoms (eg, hypertension, rapid heart rate). Instruct patient to avoid alcohol and other CNS depressant medications while taking tizanidine. Instruct patient to get up slowly from a lying or sitting position and to avoid sudden position changes to prevent postural hypotension. Instruct patient to lie or sit down if they experience dizziness, light-headedness, and/or faintness when standing. Advise patient to report frequent episodes of dizziness and/or faintness with position changes to health care provider. Caution patient that hot tubs and hot showers or baths may make dizziness and light-headedness worse. Advise patient to take sips of water, suck on ice chips or sugarless hard candy, or chew sugarless gum if dry mouth occurs. Advise patient that drug may cause drowsiness and/or dizziness and to use caution while driving or performing other tasks requiring mental alertness until tolerance is determined. Advise patient to notify health care provider if any of the following occur: dark urine, excessive drowsiness, pain below right side of chest, unexplained appetite loss or flu-like symptoms, yellowing of skin or eyes.