Optimization of primaquine diphosphate tablet formulation for controlled drug release using the mixture experimental design.

A tablet formulation based on hydrophilic matrix with a controlled drug release was developed, and the effect of polymer concentrations on the release of primaquine diphosphate was evaluated. To achieve this purpose, a 20-run, four-factor with multiple constraints on the proportions of the components was employed to obtain tablet compositions. Drug release was determined by an in vitro dissolution study in phosphate buffer solution at pH 6.8. The polynomial fitted functions described the behavior of the mixture on simplex coordinate systems to study the effects of each factor (polymer) on tablet characteristics. Based on the response surface methodology, a tablet composition was optimized with the purpose of obtaining a primaquine diphosphate release closer to a zero order kinetic. This formulation released 85.22% of the drug for 8 h and its kinetic was studied regarding to Korsmeyer-Peppas model, (Adj-R(2) = 0.99295) which has confirmed that both diffusion and erosion were related to the mechanism of the drug release. The data from the optimized formulation were very close to the predictions from statistical analysis, demonstrating that mixture experimental design could be used to optimize primaquine diphosphate dissolution from hidroxypropylmethyl cellulose and polyethylene glycol matrix tablets.

Climate as the most important factor determining anti-fungal biocide performance in paint films.

The effect of Pigment Volume Content (PVC) on fungal growth on acrylic paint formulations with and without biocide, exposed to weathering in three different climatic regions in Brazil for four years, was studied. Latex paints, with PVC of 30%, 35% and 50%, were applied to autoclaved aerated concrete blocks pre-covered with acrylic sealer and acrylic plaster. They were exposed to equatorial, tropical and temperate climates in north, south-east, and south Brazil. Cladosporium was the most abundant fungal genus detected in the biofilm on the surfaces of all paint formulations at all sites after four years. Heaviest fungal colonization occurred in the tropical south-east and lightest in the temperate south of the country, but more phototrophs, principally cyanobacteria, were detected in the equatorial region. PVC and presence of biocides were shown to be of less importance than environmental conditions (irradiance, humidity and temperature) for biofilm formation and consequent discolouration. These results have important implications for testing of paint formulations.

Optimization of poorly compactable drug tablets manufactured by direct compression using the mixture experimental design.

The poor flowability and bad compressibility characteristics of paracetamol are well known. As a result, the production of paracetamol tablets is almost exclusively by wet granulation, a disadvantageous method when compared to direct compression. The development of a new tablet formulation is still based on a large number of experiments and often relies merely on the experience of the analyst. The purpose of this study was to apply experimental design methodology (DOE) to the development and optimization of tablet formulations containing high amounts of paracetamol (more than 70%) and manufactured by direct compression. Nineteen formulations, screened by DOE methodology, were produced with different proportions of Microcel 102, Kollydon VA 64, Flowlac, Kollydon CL 30, PEG 4000, Aerosil, and magnesium stearate. Tablet properties, except friability, were in accordance with the USP 28th ed. requirements. These results were used to generate plots for optimization, mainly for friability. The physical-chemical data found from the optimized formulation were very close to those from the regression analysis, demonstrating that the mixture project is a great tool for the research and development of new formulations.