Three-layer tablet

Constant release is not always the desired solution for controlled drug administration some therapeutic situations require consecutive pulses. A biphasic oral delivery system able to release an immediate dose of therapeutic agent as well as a further pulse of drug after some hours would, useful. In order to obtain such a desired release performance, a new system (three-layer tablet) has been designed with the following characteristics ... 

To obtain such a pulsed released pattern, a system based on a three-layer tablet with the following characteristics has been designed. 

Therefore, we prepared and tested compressed three-layer tablets, covered on all surfaces, except for one part of the first dose, with an impermeable coating. We employed ibuprofen as a model drug, hydroxypropylmethylcelluloses as components of the control barrier and some superdisintegrants as the energy source [13]. 

Operating as described, cylindrical three-layer tablets were prepared, weighing about 900 mg and having two layers of active substance separated by a barrier layer of water swellable polymer mixture (granulate B). 

A nude three-layer tablet was placed in a specially designed rotating bored holder so that only one of the drug layers was lodged into the holder itself, one portion of the tablet being exposed. 

A release pattern with two pulses was obtained from a three-layer tablet consisting of two drug-containing layers, separated by a drug-free gellable polymeric barrier layer. " The three-layer tablet (Fig. 4) was coated on three sides with an impermeable coating... 

A coating can be applied by compression using specially designed tablet presses. The same process can be used to produce layered tablets which can comprise two or even three layers if complete separation of the ingredients is required. This process is used when physical separation of ingredients is desired due to incompatibility or to produce a repeat-action product. The formulation can also be designed to provide an immediate and a slow-release component. Release rates can be controlled by modification of the geometry, the composition of the core, and the inclusion of a membrane layer. 

Talc is a three-layered magnesium sheet with lubricant properties it is rarely found as a pure entity in nature. The particle size varies considerably (1) depending on the manufacturing process, and may be an important factor in the development of adverse effects. Talc is principally used as inert filler material in medicinal tablets or as a drjdng ingredient in baby powders. The adverse effects of talc include empyema, dysrhythmias, and respiratory failure (2). 

Guar gum based three-layer matrix tablets for oral controlled delivery of highly soluble metoprolol tartrate as a model drug have been evaluated (26). 

Krishnaiah, Y, Karthikeyan, R., Gouri Sankar, V., Satyanarayana, V. Three-layer guar gum matrix tablet formulations for oral controlled delivery of highly soluble trimetazidine dihydrochloride. J. Controlled Release 81(1), 45-56 (2002)... 

Soluble matrix systems. The third matrix system is based on hydrophilic polymers that are soluble in water. For these types of matrix systems, water-soluble hydrophilic polymers are mixed with drugs and other excipients and compressed into tablets. On contact with aqueous solutions, water will penetrate toward the inside of the matrix, converting the hydrated polymer from a glassy state (or crystalline phase) to a rubbery state. The hydrated layer will swell and form a gel, and the drug in the gel layer will dissolve and diffuse out of the matrix. At the same time, the polymer matrix also will dissolve by slow disentanglement of the polymer chains. This occurs only for un-cross-linked hydrophilic polymer matrices. In these systems, as shown in Fig. 5.3, three fronts are formed during dissolution9-11 ... 

One example most recently developed is a split die consisting of three sections (Figure 10) [64], Integrating the sensing web in a thin middle layer isolates stress measurement to a narrow band around the tablet and gives much closer approximation to the true stress. Further die wall force measurement is linear and independent of tablet height and position as it is uncoupled from all other die wall stresses and strains. Further it is designed in the shape of a conventional die and can be mounted without modification into a die table. 

Goto, T., Tanida, O., Yoshinaga, T., Sato, S., Ball, D. J., Wilding, I. R., Kobayashi, E., and Fujimura, A. (2004), Pharmaceutical design of a novel colon-targeted delivery system using two-layer-coated tablets of three different pharmaceutical formulations, supported by clinical evidence in humans, I. Controlled Release, 97, 31-42. 

Three-dimensional printing was used for the production of bilayer tablets. Hydroxypropyl methyl cellulose and poly(acrylic add) were used as a hydrophilic matrix for the formation of a sustained release layer. The drug release is comparable with commercial counterparts. 

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