The aim of present investigation is to develop press coated tablet, a dry-coated device for pulsatile drug delivery of a pain relieving drug using different hydrophilic and hydrophobic polymers. It is intended to be used mainly in the therapy of pain symptoms which depend on circadian rhythms. The drug delivery system will be designed to deliver the drug at such a time when it could be most needful to patient of rheumatoid arthritis and fibromyalgia [1]. It will be aimed to have a lag time of four hours so that, the system is taken at the bed time and expected to release the drug after a period of 4 hours at mid night time when such pain are at peak and disturbs sleep. Such time-controlled pulsatile drug delivery can be achieved mainly with cores containing Tapentadol hydrochloride as active agent. Core formulations, characterized by different release rates and mechanisms, will be coated by compression with an outer shell of different polymeric barrier layers of hydrophobic and hydrophilic polymers. The coatings prevent drug release from the core until the polymeric shell is completely eroded or swollen. The release profile of press coated tablet is supposed to exhibit a lag time followed by burst release, in which outer shell ruptured into two halves. The dissolution profiles of uncoated cores and press-coated devices will be compared. Various evaluation tests will be carried out to ensure the best quality formulation. The factors influencing on lag time such as type of polymeric shell and outer coating weight will be also investigated. The surface morphology of the tablet was examined by a scanning electron microscopy [2]. Differential scanning calorimeter and Fourier transformed infrared spectroscopy study showed compatibility between drug and coating material.
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