bioavailability

  Microemulsions are clear, thermodynamically stable, isotropic mixtures of oil, water and surfactant, frequently in combination with a co-surfactant. They offer numerous advantages like improved solubilization of both hydrophilic and lipophilic drugs, better bioavailability, prolong and targeted release, enhanced permeation across biological membranes, protection against oxidation, better stability and ease of manufacturing as well as processing. These systems are currently of interest to the pharmaceutical scientist because of their unique characteristics and considerable potential to act as drug delivery carrier by incorporating a wide range of drug molecules. In order to appreciate the potential of microemulsions as delivery carrier, this review gives an overview of the microemulsion properties, formulation, phase behaviour, characterization and application of microemulsions as a drug delivery carrier.

Curcumin a hydrophobic poly-phenol is derived from turmeric, the rhizome of the herb Curcuma longa L. Curcumin has been shown to exert anti-depressant effects in rodent models. However, poor bioavailability of curcumin curbs its usage as a therapeutic agent. In view of the above curcumin loaded solid lipid nanoparticles (C-SLNs) were prepared and evaluated for the antidepressant effect of acute administration of C-SLNs (1, 2.5, 5 and 10 mg/kg, p.o.) in the forced swim model of depression in mice. C-SLNs exhibited 47.42%, 67.39%, 31.67% and 36.2% reduction in immobility time after administration of 1, 2.5, 5 or 10 mg/kg dose (p.o.) respectively. Free curcumin however did not result in a significant reduction, except at 2.5 mg/kg, which could produce a reduction of 21.7% but was still 2.83 times lower than the effect obtained with a similar dose of C-SLNs. The results obtained may be assigned to the therapeutic amounts of curcumin reaching the brain. Thus, C-SLNs with their improved bioavailability and permeability possess higher anti-depressant potential upon administration of a single and a much lower dose when compared to free curcumin.

One of the most feasible approaches for achieving a prolonged and predictable drug delivery profiles in the GIT is to control the gastric residence time (GRT) using gastroretentive dosage forms. The aim of the present study is to prepare the floating microspheres of ketoprofen to sustain the drug release for longer time to overcome the short half life of the drug. The microspheres were prepared by emulsification-solvent evaporation technique using ethyl cellulose and heat denaturation technique using egg albumin as a natural polymer. The optimization of microspheres was carried out based on pentagonal design using response surface methodology. The floating microspheres were evaluated for micromeritic properties, particle size, percentage yield, in-vitro buoyancy, entrapment efficiency, drug polymer compatibility, scanning electron microscopy and in-vitro drug release studies. The prepared microspheres exhibited prolonged drug release (> 9 h) and remained buoyant for > 24 h. The mean particle size increased and the drug release rate decreased at higher polymer concentration. The optimized formulation of ethyl cellulose microspheres (KEC-OP) exhibited prolonged drug release of 88.31 % up to 10 h demonstrating zero order kinetics and Case II transport release mechanism where as optimized formulation of egg albumin (KEA-OP) showed drug release of 96.78 % up to 9 h demonstrating peppas kinetics and Case II transport release mechanism.

Piperine (1-peperoyl piperidine), a pungent alkaloid, is found in various Pipper species. Piperine produces antioxidant, antiplatelet, anti-inflammatory, antihypertensive, hepatoprotective, antithyroid, antitumor, antiasthmatic activities and also a fertility enhancer. Piperine enhances absorption from gastrointestinal tract by various mechanisms and reduces gut metabolism of drugs. Piperine modulates membrane dynamics and lipid environment and increases permeability at site of absorption Molecular structure of piperine is suitable for enzyme inhibition and it inhibits various metabolizing enzymes like cytochrome bs, NADPH cytochrome, CYP3A4, UDP-glucose dehydrogenase (UDP-GDH), aryl hydrocarbon hydroxylase (AAH) and UDP-glucuronyl transferase. Structural modification of piperine provides selective inhibitors of various cytochrome p450 enzymes. Inhibition of these enzymes by piperine results in enhanced bioavailability of drugs and nutrients like oxytetracyclin, metronidazole, ampicillin, norfloxacin, ciprofloxacin, acefotaxime, amoxicillin trihydrate, curcumin, beta-carotene, carbamazepine, gallic acid, nimesulide, tiferron, nevirapine, pentobarbitone, phenytoin, resveratrol, vasicine and sparteine by different mechanisms. Thus piperine is an absorption enhancer and a potent inhibitor of drug metabolism. Key words: Piperine, Metabolism inhibitor, Absorption enhancer, Bio-enhancer, bioavailability

  The objective of present study is to improve the dissolution rate of Acyclovir a poorly water soluble drug by solid dispersion technique using a water soluble carrier, PEG-6000, urea, mannitol. The solid dispersions are prepared by physical method, co-grinding method and solvent evaporation method. The prepared solid dispersions showed an enhancement in dissolution rate and solubility compared to plain drug. In vitro release profiles of all SDs were comparatively evaluated and also studied against pure acyclovir. Faster dissolution was exhibited by solid dispersion containing 1:4 ratio of drug: PEG-6000. The increase in dissolution rate of the drug may be due to increase in wettability, hydrophilic nature of the carrier and due to reduction in drug crystallinity. The prepared solid dispersion was subjected for % practical yield, drug content, infrared (IR) spectroscopic, differential scanning calorimetry (DSC). FT‐IR spectra revealed no chemical incompatibility between drug and PEG-6000.Drug– polymer interaction was investigated using differential scanning calorimetry (DSC) studies. Key words: Solid dispersions, carriers, solubility enhancement, poorly soluble drugs, bioavailability

  Buccal mucosa is the preferred site for both systemic and local drug action. The mucosa has a rich blood supply and it relatively permeable. Mucoadhesion can be defined as a state in which two components, of which one is of biological origin, are held together for extended periods of time by the help of interfacial forces. Mucoadhesion is a complex phenomenon which involves wetting, adsorption and interpenetration of polymer chains. Buccal mucoadhesive systems remain in close contact with the absorption tissue, the mucous membrane releasing the drug at the action site leading to increase in bioavailability (both local and systemic effects). Extending the residence time of a dosage form at a particular site and controlling the release of drug from the dosage form are useful especially for achieving controlled plasma level of the drug as well as improving bioavailability. In the present review article discusses with the buccal membrane, theory and kinetics behind buccal mucoadhesion, different types of buccal formulation advantages and disadvantages of buccal mucoadhesive drug delivery system.