Abstract
Metoprolol is a β1 adrenergic blocker used in treatment of heart diseases. Metoprolol (100mg) tablets was formulated as a modified release oral system utilizing the concept of bilayer system, first layer contained (30mg) as immediate release and the other (70mg) in the sustained release matrix. The immediate release layer consisted of lactose or microcrystalline cellulose as diluents with sodium starch glycolate or sodium croscarmellose as disintegrants. The result showed that the layer contains microcrystalline cellulose and 2% sodium starch glycolate gave disintegration time similar to that of conventional metoprolol tartrate tablet. This result was subjected in the subsequent preparation of the bilayer tablet. The sustained release layer was prepared using three polymers: ethylcellulose (EC), Hydroxypropyl methylcellulose (HPMC) and hydroxyl ethylcellulose (HEC) as retardant materials. It was found that the combination of EC with HPMC in ratio of 2:1 in F11 was best formula because of it’s release profile and the tablet integrity and dimensions were conserved for the period of the test, but according to similarity factor (f Â2Â), F15 (which contained EC:HPMC in ratio 2:1 with polyvinyl pyrrolidone (PVP) as a binder) was the best formula showed higher (f2Â) among all other formulas and equals to 72.3 comparing to reference product.
 Key words: Metoprolol, Bilayer tablet, Immediate release, Sustained release.
Highlights
Tablets may be defined as solid pharmaceutical dosage forms containing drug substances with or without suitable diluents and have traditionally prepared by either compression, or molding methods
Preparation of Immediate Release (IR) Granules Different formulas were prepared using wet granulation method to achieve most acceptable pharmacopial requirements and consider as comparable test with the reference one (Metoprolol tartrate UK limited 50 mg) tablet.After weighing the drug and the excipients enough to prepare 40 tablets in dried form, and blend the ingredients using mortar and pestle, the powders were mixed with binding solution (10% alcoholic starch paste) gradually until proper ball test consistency was resulted.The wet mass was screened through sieve (10 mesh) and dried in pre warmed oven at 60 oC for one hour
All the disintegration times of the prepared formulas are shown in table (3) are within the pharmacopial requirements but the IR3 is the closest one to the standard metoprolol tartrate 50 mg conventional tablet so it was used for the further bilayer formulation
Summary
Tablets may be defined as solid pharmaceutical dosage forms containing drug substances with or without suitable diluents and have traditionally prepared by either compression, or molding methods. Type of modified release, are prepared by compressing several different granulations fed into a die in succession, one on top of another, in layers. Each layer may contain a different medicinal agent, separated for reasons of chemical or physical incompatibility, staged drug release, or for unique appearance of the layered tablet (3). Rahmanz Z. et al, designed a bilayer floating tablet of captopril in which one layer responsible for floating of the tablet for prolongation the gastric residence time with a controlled release mechanism(4). The bioavailability of propranolol was enhanced by formulating a bilayer and multilayer buccal mucoadhesive tablet in which one layer adhere to the buccal mucosa so localized the drug in the oral cavity and avoid hepatic first pass metabolism (5)
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