Yamsani Madhusudan Rao

The present study is concerned with formulation and evaluation of mucoadhesive buccal patches containing antihypertensive drug i.e. Timolol to avoid the first pass effect and to improve its bioavailability with reduction in dosing frequency and also dose related side effects. The patches were prepared by solvent casting technique with varying concentration of HPMC E15 as polymer and propylene glycol as the plasticizer and evaluate their physicochemical properties, in vitro drug release, moisture absorption, surface pH, mechanical properties, in vitro bio adhesion, and ex vivo drug permeation through porcine buccal membranes from optimized buccal patch. The physicochemical interaction between timolol and polymer was investigated by Fourier transform infrared spectroscopy. Moisture absorption, surface pH, tensile strength, elongation at break, peak detachment force and work of adhesion values of the optimized formulation F4 were found to be 124±10.59%, pH 6.61±0.28, 3.89 kg/mm2, 14.16 mm2, 4.92±0.06N and 0.65±0.08mJ respectively. Formulation F4 showed 68.99 ±1.67% of the drug release in in vitro condition and follows zero order kinetics and drug release mechanism follows non-fickian diffusion. Ex vivo drug permeation through porcine buccal membrane was performed and 58.52±1.59% of the drug permeated in 6 hrs with flux 0.22 mg/h/cm2.The optimized formulation F4 with permeation enhancer tween 80 (1% v/w) showed drug release 64.47±1.63 % in 6 hrs with flux 0.33mg/h/cm2. FTIR studies showed no evidence of interaction between the drug and polymers. Drug release from the buccal patches follows desire controlled release phenomenon as required in mucoadhesive drug delivery.

A new multi-layer tablet design has recently been proposed for constant drug release: It consists of a drug-free barrier layer on one or both bases of an active core (hydrophilic matrix). This partial coating modulates the core hydration process and reduces the surface area available for drug release. The consequence is an extended release that draws close to a linear release profile. These devices are primarily intended for soluble drugs, while an excessive reduction of the release rate may be obtained with drugs of low solubility. In these devices, time-dependent polymeric barrier is planned to control the release of soluble drugs. Oral Controlled release matrix tablets and layered matrix tablets can be formulated for highly water soluble drugs and sparingly soluble drugs by using polymers in the matrix core and as release retardant layers. This devices delivery the drugs to the colon. This review focuses on the application of the multilayered matrix tablets in the design of controlled released dosage forms employing various types of polymers and layered on the matrices core. Key words: Matrix core, multilayered matrix tablets, zero order release, release retardant layers