الفهرس 
A pharmaceutical study on certain floating controlled release formulations of tizanidine hydrochloride
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Abstract
Tizanidine (Tiz) is an agonist at Ü2-adrenergic receptor sites and presumably reduces spasticity by increasing presynaptic inhibition of motor neurons. In animal models, Tizanidine has no direct effect on skeletal muscle fibers or the neuromuscular junction, and no major effect on monosynaptic spinal reflexes. The effects of Tizanidine are greatest on polysynaptic pathways. The overall effect of these actions is thought to reduce facilitation of spinal motor neurons. Tiz suffers from low absolute bioavailability (30-40%) and short elimination half life (4.2 h) following oral administration; probably due to the considerable first-pass metabolism in the liver. In the current work, gastroretentive floating controlled release formulations of TiZ were developed in a trial to overcome the first-pass metabolism of the drug, to improve its low oral bioavailability and to reduce dosing frequency.The work in this thesis is thus divided into two chapters: Chapter Ї: Formulation, in Vitro and in vivo evaluation of Tizanidine Hydrochloride gastroretentive floating controlled release formulations prepared by effervescent technique Chapter ЇЇ: Formulation , in Vitro and in vivo evaluation of Tizanidine Hydrochloride gastroretentive floating controlled release formulations prepared by sublimation technique