Novel valsartan-loaded solid dispersion with enhanced bioavailability and no crystalline changes.

With the aim of developing a novel valsartan-loaded solid dispersion with enhanced bioavailability and no crystalline changes, various valsartan-loaded solid dispersions were prepared with water, hydroxypropyl methylcellulose (HPMC) and sodium lauryl sulphate (SLS). Effects of the weight ratios of SLS/HPMC and carrier/drug on both the aqueous solubility of valsartan and the drug-release profiles of solid dispersions were investigated. The physicochemical properties of solid dispersions were characterized using scanning electron microscope (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The bioavailability of the solid dispersions in rats was evaluated compared to valsartan powder and a commercial product (Diovan). Unlike the conventional solid dispersion system, the valsartan-loaded solid dispersion had a relatively rough surface and did not change the crystalline form of the drug. It was suggested that the solid dispersions were formed by attaching hydrophilic carriers to the surface of the drug, thus changing from a hydrophobic to a hydrophilic form without changing the crystalline form. The drug-loaded solid dispersion composed of valsartan/HPMC/SLS at a weight ratio of 3/1.5/0.75 improved the drug solubility by about 43-fold. It gave a higher AUC, C(max) and shorter T(max) compared to valsartan powder and the commercial product. The solid dispersion improved the bioavailability of the drug in rats by about 2.2 and 1.7-fold in comparison with valsartan powder and the commercial product, respectively. Thus, the valsartan-loaded solid dispersion would be useful for delivering poorly water-soluble valsartan with enhanced bioavailability and no crystalline changes.

Evaluation of physicochemical properties, skin permeation and accumulation profiles of salicylic acid amide prodrugs as sunscreen agent.

Various amide prodrugs of salicylic acid were synthesised, and their physicochemical properties including lipophilicity, chemical stability and enzymatic hydrolysis were investigated. In vivo skin permeation and accumulation profiles were also evaluated using a combination of common permeation enhancing techniques such as the use of a supersaturated solution of permeants in an enhancer vehicle, a lipophilic receptor solution, removal of the stratum corneum and delipidisation of skin. Their capacity factor values were proportional to the degree of carbon-carbon saturation in the side chain. All these amides were highly stable in acetonitrile and glycerine. Amide prodrugs were converted to salicylic acid both in hairless mouse liver and skin homogenates. N-dodecyl salicylamide (C12SM) showed the lowest permeation of salicylic acid in skin compared to the other prodrugs, probably due to its low aqueous solubility. It had a high affinity for the stratum corneum and its accumulation was restricted to only the uppermost layer of skin. Thus, this amide prodrug could be a safer topical sunscreen agent with minimum potential for systemic absorption.

Enhanced oral bioavailability of docetaxel in rats by four consecutive days of pre-treatment with curcumin.

As with many other anti-cancer agents, docetaxel is a substrate for ATP-binding cassette transporters such as P-glycoprotein and its metabolism is mainly catalysed by CYP3A. In order to improve the oral bioavailability of docetaxel, a component of turmeric, curcumin, which can down-regulate the intestinal P-glycoprotein and CYP3A protein levels, was used for the pre-treatment of rats before the oral administration of docetaxel. Curcumin (100 mg/kg) did not significantly modify the pharmacokinetics of docetaxel when given orally 30 min before the administration of docetaxel. However, the C(max) of docetaxel in rats pre-treated with curcumin for four consecutive days was significantly increased (p<0.01) by about 10 times compared to that of the docetaxel control, and the area under the plasma concentration-time curve (AUC) was about eight times higher than that of the control. Consequently, the absolute bioavailability of docetaxel in the treatment group (four days of curcumin at 100 mg/kg) was about 40%, which was a significant increase of about eightfold in comparison to the control value. Thus, the oral bioavailability of docetaxel was enhanced by the co-administration of regular curcumin. It could be possible to administer docetaxel orally, besides the established i.v. route.

Novel elastic scattering model for the understanding of the Anomalous transmittance for Au nanoparticle layer.

The optical transmission spectra of several samples of gold nanoparticle layers were examined using a modified Drude model proposed with a novel elastic scattering parameter, gamma'. Although the measured transmission spectra deviated from the simple calculation from Mie scattering, it was explained well by the modified model assuming elastic and inelastic scattering in the form of the collision frequency of free electrons within a metal particle due to the particle boundary. The particle-size and inter-particle-distance dependences of gamma' were extracted within the framework of the proposed model from the curve of best fit of the transmittance spectra.