Dual Mechanism of Action

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Chart displaying the effects on the brain and spinal chord (See lists below).

In the Brain:

In Animal Studies:
Reduces activity in the Locus Ceruleus^1,6

In the Spinal Cord:

Primary action on polysynaptic pathways to:
Reduce release of excitatory neurotransmitters^1,6
Reduce the sensitivity of the post-synaptic neuron to excitatory neurotransmitters^1,6

Although the complete mechanism of action of Zanaflex Capsules^® (tizanidine hydrochloride) is not fully elucidated, it is believed that through these actions, Zanaflex Capsules^® (tizanidine hydrochloride) reduce muscle tone and spasm, without reducing muscle strength. Animal studies show no direct effect on the neuromuscular junction or muscle fibers.^1,6

Please see below for Important Safety Information.

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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