A review of analytical methods for the determination of four new phosphodiesterase type 5 inhibitors in biological samples and pharmaceutical preparations

The introduction of oral phosphodiesterase type 5 inhibitor therapy in 1998 revolutionized the treatment of erectile dysfunction. Erectile dysfunction is the most common sexual problem in men. It often has a profound effect on intimate relationships and quality of life. The analysis of pharmaceuticals is an important part of the drug development process as well as for routine analysis and quality control of commercial formulations. Whereas the determination of sildenafil citrate, vardenafil and tadalafil are well documented by a variety of methods, there are few publications about the determination of udenafil, lodenafil carbonate, mirodenafil and avanafil. The paper presents a brief review of the action mechanism, adverse effects, pharmacokinetics and the most recent analytical methods that can determine drug concentration in biological matrices and pharmaceutical formulations of these four drugs.A introdução da terapia oral com inibidores da fosfodiesterase tipo 5, em 1998, revolucionou o tratamento da disfunção erétil. A disfunção erétil é o problema sexual mais comum em homens. Muitas vezes tem um efeito profundo nas relações íntimas e na qualidade de vida. A análise de produtos farmacêuticos é uma parte importante do processo de desenvolvimento de fármacos, bem como para a análise de rotina e controle de qualidade das formulações comerciais. Enquanto a determinação do citrato de sildenafila, vardenafila e tadalafila está bem documentada por uma variedade de métodos, existem poucas publicações sobre a determinação de udenafila, carbonato de lodenafila, mirodenafila e avanafila. O artigo apresenta uma breve revisão do mecanismo de ação, efeitos adversos, farmacocinética e os mais recentes métodos analíticos, que podem determinar a concentração do fármaco em matrizes biológicas e formulações farmacêuticas destes quatro fármacos

Chemical availability of mercury in stream sediments from the Almaden area, Spain

cited By 37International audienceThe chemical speciation, fractionation and availability of mercury in sediments from a cinnabar mining area (Almaden, Spain) was studied with different extraction and analytical procedures, in order to determine the degree to which the ecosystem is harmed by this pollutant. Three total extraction procedures, a sequential extraction and the speciation of organo-mercury compounds were performed in nine sediment samples. In the study area, although concentrations of mercurycan be extremely high (up to 1000 mg kg-1), no organo-mercury compounds were detected (< 2 μg kg-1) and the availability of this element seems restricted. One of the methods for total extraction presented considerably lower recovery in Almaden's sediments, yet the results were controlled with certified reference materials. This disagreement was attributed to the fact that the mercury is in a refractory form. Sequential extraction was able to show that most of the mercury is associated with sulfides (probably as metacinnabar) or in the residual refractory phase (probably as red cinnabar)

Evaluation of host-guest complex formation between a benzimidazolic derivative and cyclodextrins by UV-VIS spectrophotometry and differential scanning calorimetry

Abstract Interactions between a benzimidazolic derivative, omeprazole (OME), beta-cyclodextrin (ßCD) and a chemically modified ßCD, methyl-beta-cyclodextrin (MßCD) were investigated in aqueous solution by UV-VIS spectroscopy and in solid state by differential scanning calorimetry (DSC). Phase solubility studies were used to evaluate the complexation in aqueous solution. The two solubility diagrams obtained were AL type, indicating the formation of a drug-cyclodextrin complex with 1:1 stoichiometry. The complex of OME with MßCD showed a higher stability constant (K S) than those with ßCD. Some evidences of inclusion complexation in solid state were obtained from DSC. Only in thermal curves of OME-ßCD lyophilized product and in OME-MßCD spray-dried and lyophilized systems the melting point of the drug disappeared completely suggesting the possible formation of an inclusion complex