Modified release tizanidine: a review.

The pharmacokinetic and clinical properties of a modified release formulation of the alpha 2-adrenergic agonist tizanidine are reviewed. Therapy with conventional tizanidine tablets is effective in the relief of spasticity, but it has a short half-life, resulting in it having to be administered three or four times daily. The modified release capsules have retard characteristics which allow the drug to be given as a once-daily dosage. Single- and multiple-dose pharmacokinetic studies in healthy volunteers have shown that the relative bioavailability of the modified release formulation is similar to that of conventional tablets and is unaffected by food. Clinical studies have shown that modified release tizanidine improved spasticity and disability in approximately 94% and 79%, respectively, of spastic patients. Adverse effects were observed in about 33% of patients. Mild, transient muscular weakness was the most common effect, but it did not require termination of treatment. Body weight, blood pressure, heart rate and haematological or biochemical measures were not adversely affected. The initial recommended dose of modified release tizanidine is one capsule per day of 6 mg, which may be increased gradually to 24 mg. A daily dose of 12 mg modified release tizanidine was used in 50% of patients studied.