ABSTRACTgroup, is a centrally acting analgesic with weak opioid agonist properties. Tramadol has been proved to be effective in both experimental and clinical pain without causing serious cardiovascular or respiratory side effects. 1 The half-life of the drug is about 5.5 hours and the usual oral dosage regimen is 50 to 100 mg every 4 to 6 hours with a maximum dosage of 400 mg/day.2 To reduce the frequency of administration and to improve patient compliance, a sustained-release formulation of tramadol is desirable. The drug is freely soluble in water and hence judicious selection of release retarding excipients is necessary to achieve a constant in vivo input rate of the drug. The most commonly used method of modulating the drug release is to include it in a matrix system.3 Hydrophilic polymer matrix systems are widely used in oral controlled drug delivery because of their flexibility to obtain a desirable drug release profile, cost-effectiveness, and broad regulatory acceptance. 4 The drug release for extended duration, particularly for highly water-soluble drugs, using a hydrophilic matrix system is restricted due to rapid diffusion of the dissolved drug through the hydrophilic gel network. For such drugs with high water solubility, hydrophobic polymers (waxes) are suitable as matrixing agents for developing sustained-release dosage forms.5 Hydrophobic polymers provide several advantages, ranging from good stability at varying pH values and moisture levels to well-established safe applications.The effect of concentration of hydrophilic (hydroxypropyl methylcellulose [HPMC]) and hydrophobic polymers (hydrogenated castor oil [HCO], ethylcellulose) on the release rate of tramadol was studied. Hydrophilic matrix tablets were prepared by wet granulation technique, while hydrophobic (wax) matrix tablets were prepared by melt granulation technique and in vitro dissolution studies were performed using United States Pharmacopeia (USP) apparatus type II. Hydrophobic matrix tablets resulted in sustained in vitro drug release (>20 hours) as compared with hydrophilic matrix tablets (<14 hours). The presence of ethylcellulose in either of the matrix systems prolonged the release rate of the drug. Tablets prepared by combination of hydrophilic and hydrophobic polymers failed to prolong the drug release beyond 12 hours. The effect of ethylcellulose coating (Surelease) and the presence of lactose and HPMC in the coating composition on the drug release was also investigated. Hydrophobic matrix tablets prepared using HCO were found to be best suited for modulating the delivery of the highly watersoluble drug, tramadol hydrochloride. KEYWORDS: tramadol, hydrogenated vegetable oil, hydroxypropyl methylcellulose, ethylcellulose, melt granulationIn the present study, various matrix systems were designed and tested for controlled delivery of tramadol. The objectives of the study were (1) to investigate the performance of hydrophilic and hydrophobic matrix systems in controlling the release of this freely soluble drug, and (2) to inve...

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Uranium is the basic raw material for a nuclear energy programme. Uranium ore is processed in India by the well-known method of sulphuric acid, ion-exchange concentration and its final precipitation as magnesium diuranate-'yellow cake'. We have established a process for uranium recovery from the tailings of copper concentrators which also enables recovery of small amounts of copper, nickel and molybdenum present in the uranium ore. Another major activity of this centre has been the exploitation of mineral-rich beach sands to produce ilmenite, rutile, zircon and monazite. Downstream industries have also been established for chemical processing of these minerals. Production of niobium from low-grade ores and beryllium from beryl ore is also being carried out on a moderate scale.

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