Tizanidine clinical effects

Renal impairment Tizanidine clearance is reduced by greater than 50% in elderly patients with renal insufficiency (creatinine clearance less than 25 mL/min) compared to healthy elderly subjects this would be expected to lead to a longer duration of clinical effect. 

Clinical trials with oral tizanidine report comparable efficacy in relieving muscle spasm to diazepam, baclofen, and dantrolene. However, tizanidine produces a different spectrum of adverse effects, including drowsiness, hypotension, dry mouth, and asthenia. The dosage requirements vary markedly among patients, and individual dosage titration is necessary to achieve an optimal clinical effect. 

Tizanidine is an a2-adrenergic agonist [581] which is a good and well tolerated muscle relaxant used to treat muscular spasms and spastic conditions [582-587], Its action on adrenoceptors and its antinociceptive effect are well studied it depresses polysynaptic excitation of spinal motor neurones [588-591], Recent clinical trials demonstrated the value of tizanidine in the treatment of tension headaches [592] and lower back pain [593],... 

For combined orai contraceptives, the increase in exposure to tizanidine is a more moderate fourfold. The manufacturer states that clinical response or adverse effects might occur at lower doses of tizanidine in patients taking oral contraceptives, and that during dose titration, individual doses should be reduced. Care is needed. ... 

Rifampicin moderately reduces the levels and effects of tizanidine. Because tizanidine dose is titrated to effect, this is probably not that clinically important. A small increase in dose might be required. 

Henney HR, Runyan DJ. A clinically relevant review of Tizanidine hydrochloride dose relationships to pharmacokinetics, drug safety and dose effectiveness in healthy subjects and patients. Int J Clin Pract 2008 62(2) 314-324. 

Momo K, Homma M, Matsumoto S, Sasaki T, Kohda Y. Clinical survey of tizanidine-induced adverse effects -impact of concomitant drugs providing cytochrome P450 1A2 modification Yakugaku Zasshi 2013 133 275-281. 

---