TIZANIDINE - A REVIEW OF ITS PHARMACOLOGY, CLINICAL EFFICACY AND TOLERABILITY IN THE MANAGEMENT OF SPASTICITY ASSOCIATED WITH CEREBRAL AND SPINAL-DISORDERS

The central alpha(2) adrenoceptor agonist tizanidine is a myotonolytic agent used in the treatment of spasticity in patients with cerebral o r spinal injury. Wide interpatient variability in the effective plasma concentrations of tizanidine means that the optimal dosage must be ti trated over 2 to 4 weeks for each patient (dosages of 2 to 36 mg/day h ave been used in clinical trials). Maximum effects occur within 2 hour s of administration. Antispastic efficacy has been demonstrated for ti zanidine in placebo-controlled trials, with reduction in mean muscle t one scores of 21 to 37% versus 4 to 9% for patients receiving placebo. Improvement in muscle tone occurred in 60 to 82% of tizanidine recipi ents, compared with 60 to 65% of baclofen and 60 to 83% of diazepam re cipients. Spasm frequency and clonus are also reduced by tizanidine. T he most common adverse effects associated with tizanidine are dry mout h and somnolence/drowsiness. Muscle strength, as assessed by objective means, appears not to be adversely affected by tizanidine and subject ive muscle weakness is reported less often by tizanidine recipients th an by those receiving baclofen or diazepam. Global tolerability was as sessed as good to excellent in 44 to 100% of patients receiving tizani dine, compared with 38 to 90% of baclofen and 20 to 54% of diazepam re cipients. In conclusion tizanidine is an antispastic agent with simila r efficacy to that of baclofen and a more favourable tolerability prof ile. While drowsiness is a frequently reported adverse effect with bot h agents, subjective muscle weakness appears to be less of a problem w ith tizanidine than with baclofen. Tizanidine, therefore, appears to b e an attractive therapeutic alternative for patients with spasticity a ssociated with cerebral or spinal damage.