Dosing and Administration

Zanaflex Capsules^® (tizanidine hydrochloride) are available in 2 mg, 4 mg, and 6 mg strengths

Due to the dose-related nature of the drug's most common side effects, it is prudent to begin treatment with single doses of 4 mg
Dose should be titrated in small increments of 2-4 mg to optimum effect
Experience with single doses greater than 8 mg and daily doses exceeding 24 mg is limited. Single doses should not exceed 12 mg, and total daily doses should not be greater than 36 mg

Zanaflex Capsules^® are not interchangeable with Zanaflex^® (tizanidine hydrochloride) tablets or tizanidine tablets. Zanaflex Capsules^® are not therapeutically equivalent to Zanaflex tablets or generic tizanidine tablets in the fed state.

Food and Absorption
Food has different effects on tizanidine absorption depending on the dosage forms.

Effects and Adverse Events Are Related to Plasma Levels of Tizanidine2

Significant pharmacokinetic changes including plasma level differences occur when administering Zanaflex Capsules^® (tizanidine hydrochloride) or tablets with food.^2,5
These (pharmacokinetic) differences can result in clinically important differences in effectiveness and adverse events.^2,5

As shown in the above chart, plasma levels of tizanidine increase when tablets are taken with food and decrease when capsules are taken with food.

These pharmacokinetic differences may result in clinically significant differences when switching. An increase in adverse events or a delayed/more rapid onset of activity may occur depending on the nature of the switch. Physicians should be aware of these differences in the following situations:

1. Switching administration of the tablet between the fed and fasted state
2. Switching administration of the capsules between the fed and fasted state
3. Switching between capsules and tablets

Please be sure to carefully check all Zanaflex Capsules^® (tizanidine hydrochloride) prescriptions to make sure that the correct information is dispensed to your patients.

Please see below for Important Safety Information.

Be sure your patient received what you prescribed

Zanaflex Capsules® (tizanidine hydrochloride) is a short-acting drug indicated for the management of spasticity. Because of the short duration of effect, treatment with Zanaflex Capsules® (tizanidine hydrochloride) should be reserved for those daily activities and times when relief of spasticity is most important.

Important Safety Information:

Use with fluvoxamine or ciprofloxacin is contraindicated and results in significant increases in tizanidine plasma levels.
There is a limited data base for chronic use of single doses above 8 mg and multiple doses above 24 mg per day.
Tizanidine is an alpha2-adrenergic agonist and can produce hypotension. In a single-dose study where patients were not titrated, two-thirds of patients given 8 mg of Zanaflex experienced hypotension, which may be minimized by titration of dose. The hypotensive effect is dose related and has been measured following single doses of 2 mg or more.
Tizanidine occasionally causes liver injury, most often of the hepatocellular type.
Patients should be advised that sedation may interfere with daily activities. These effects appear to be dose related.
Visual hallucinations or delusions occurred in 3% (5/170) of study patients in two North American clinical trials.
Use with caution in hepatic or renally impaired patients.
Use with oral contraceptives results in 50% decrease in tizanidine clearance.
To discontinue therapy, taper the dose in patients receiving high doses over long time periods to reduce the risk of hypertension, tachycardia and hypertonia.
In vitro studies indicate that neither tizanidine nor the major metabolites are likely to affect the metabolism of other drugs metabolized by cytochrome P450 isoenzymes.
Most common adverse events with tizanidine include dry mouth (49%), somnolence (48%), asthenia [weakness, fatigue and/or tiredness] (41%), dizziness (16%) and increased ALT (5%). Other adverse events include UTI, infection and constipation.
Food has complex effects on tizanidine pharmacokinetics, which differ for the different formulations. These pharmacokinetic differences may result in clinically significant differences when switching formulations, or changing administration during a fed or fasted state. These changes may result in increased adverse events or a delayed/more rapid onset of activity, depending on the nature of the switch.

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