The liquisolid technique is a novel approach for delivery of drugs through the oral route. This technique is suitable for poorly soluble or water insoluble drugs, highly permeable drugs (BCS Class II drugs) and also for immediate or sustained release formulations. It is a novel "Powder Solution Technology" that involves absorption and adsorption efficiencies, making use of liquid medications, drug suspensions admixed with suitable carriers, coating materials and formulated into free flowing, dry looking, non-adherent and compressible powder forms. The design of liquisolid systems are mainly intended for enhancement of solubility, dissolution rate and bioavailability of poorly water-soluble and highly lipophilic drugs. Improvement in bioavailability may be due to increased surface area, increased aqueous solubility and increased the wettability of the drug. Liquisolid technique also has the potential to be optimized for the reduction of drug dissolution rate and thereby production of sustained release systems. Overall, liquisolid technique is a most promising and novel technique for enhancing the dissolution and bioavailability of poorly water soluble drugs and sustaining drug release from tablet matrices. The current review mainly focuses on theory and applicability of liquisolid compact technique towards solubility or bioavailability enhancement. Different carriers, solvents and coating materials employed are elucidated. Literature reports on the applicability of liquisolid compact techniques over a wide range of pharmaceutical formulations are also explicated.

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A simple, rapid and sensitive RP-HPLC method was developed for the quantitative determination of tramadol hydrochloride and paracetamol in combined tablet dosage form. The chromatographic analysis was carried out on enable C18G column (250 x 4.6 mm, 5 μm) with mobile phase containing 1 % glacial acetic acid: acetonitrile (50:50 v/v). The flow rate of mobile phase was 1.0 mL/min and effluents were monitored at 272 nm. The retention times of tramadol hydrochloride and paracetamol were 2.032 min and 2.711 min, respectively. The proposed method was validated with respect to linearity, accuracy, precision, specificity and robustness. The method was found to simple, rapid and sensitive and was successfully applied to the estimation of tramadol hydrochloride and paracetamol in combined dosage form.

Gastro-retentive drug delivery systems (GRDDS) like gastro-retentive microspheres have gained immense popularity in the field of oral drug delivery. It is a widely employed approach to retain the dosage form in the stomach for an extended period of time and release the drug slowly that can address many challenges associated with conventional oral delivery, including poor bioavailability. Different innovative approaches like magnetic field assisted gastro-retention, swelling systems, mucoadhesion techniques, floating systems with or without effervescence are being applied to fabricate gastroretentive microspheres. Apart from in-vitro characterization, successful gastro-retentive microspheres development demands well designed in-vivo study to establish enhanced gastro-retention and prolonged drug release. Gama scintigraphy and MRI are popular techniques to evaluate in-vivo gastric residence time. However, checking of their overall in-vivo efficacy still remains a major challenge for this kind of dosage form, especially in small animals like mice or rat. Reported in-vivo studies with beagle dogs, rabbits, and human subjects are only a handful in spite of a large number of encouraging in-vitro results. In spite of the many advantages, high subject variations in gastrointestinal physiological condition, effect of food, and variable rate of gastric emptying time are the challenges that limit the availability of gastro-retentive microspheres in the market.

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