Avaliação, modificação e validação de metodologia para estudo de estabilidade de hidroquinona em creme
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Data
2009-06-24
Autores
Farinelli, Juliane [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O melasma é caracterizado por hipermelanose, adquirida, simétrica e irregular, situada em áreas da pele. Muitos trabalhos mostram a eficácia da hidroquinona (HQ) no processo de clareamento das manchas provocadas pelo melasma, sendo que esta já foi classificada como o despigmentante de pele mais prescrito do mundo. O maior inconveniente da HQ é que esta se oxida rapidamente, apresentando maior estabilidade em meio ácido, na faixa de 4,5 a 5,0. O estudo da estabilidade de formas farmacêuticas em geral, assegura que a forma farmacêutica se mantenha dentro dos limites estabelecidos durante o período em que garante a validade. Um fator relevante para a estabilidade é a garantia de que a fórmula não irá se oxidar. No caso da HQ, que é altamente instável por se oxidar facilmente, faz-se utilização de agentes antioxidantes, como o metabissulfito de sódio. Amostras de creme contendo 2% de HQ foram avaliadas por três metodologias diferentes (espectrofotometria com etanol como solvente; espectrofotometria de derivadas com ácido sulfúrico 0,1N como solvente e espectrofotometria de derivadas com metanol como solvente) em ensaios de estabilidade. Apenas a metodologia com metanol, mostrou-se adequada para a quantificação da HQ em ensaio de estabilidade. As metodologias com etanol e ácido sulfúrico não apresentaram eficácia. A partir da metolodogia com metanol foram avaliados os sistemas antioxidantes e os prazos de validade foram determinados para as temperaturas de 45°C e 30°C. O ácido α lipóico promoveu melhor estabilidade para a HQ que o metabissulfito de sódio. O metabissulfito de sódio foi o antioxidante que melhor manteve a características iniciais do creme. O prazo de validade para a HQ sem antioxidante foi de 24 h, com metabissulfito de sódio foi de 87 h e com ácido α lipóico foi de 125 h à 45°C. Para a temperatura ambiente foi avaliado somente o creme sem antioxidante que apresentou prazo de validade de 72 h.
Melasm is characterized as an acquired, symmetric and irregular hypermelanosis in the skin. Many works have shown the efficacy of hydroquinone (HQ), in the lighting process of melasm stains, and it has already been classified as the most prescribe skin lightning of the world. The major inconvenient of HQ is that it fastly oxides, showing more instability in acid media, in the range of 4.5 a 5.0. Stability studies of pharmaceuticals in general, ensure that the limits established during the shelf life can be kept. A very important factor for stability is the guarantee that the pharmaceutical will not oxide. As HQ is very instable for its fast oxidation, antioxidants as sodium metabissulfite are used. Cream samples with 2% of HQ were evaluated by three different methodologies (spectrophometric using ethanol as solvent, derivative spectrophotometric using sulfuric acid 0,1N as solvent and derivative spectrophotometric using methanol as solvent) in stability tests. Only the methodology with methanol had presented satisfactory results for quantification of HQ in stability tests. The methodologies with ethanol as well with sulfuric acid did not shown efficacy. From methanol methodology the antioxidants systems and the shelf life were evaluated for temperatures of 45°C and 30°C. Alpha lipoic acid promoted better HQ stability than sodium metabissulfite. Sodium metabissulfite was the antioxidant that best kept the initial characteristics of the cream. Shelf life for HQ without antioxidant was 24h, with sodium metabissulfite was 87h and with alpha lipoic acid was 125 h at 45°C. At 30°C it was evaluated only the sample with antioxidant which showed shef life of 72 h.
Melasm is characterized as an acquired, symmetric and irregular hypermelanosis in the skin. Many works have shown the efficacy of hydroquinone (HQ), in the lighting process of melasm stains, and it has already been classified as the most prescribe skin lightning of the world. The major inconvenient of HQ is that it fastly oxides, showing more instability in acid media, in the range of 4.5 a 5.0. Stability studies of pharmaceuticals in general, ensure that the limits established during the shelf life can be kept. A very important factor for stability is the guarantee that the pharmaceutical will not oxide. As HQ is very instable for its fast oxidation, antioxidants as sodium metabissulfite are used. Cream samples with 2% of HQ were evaluated by three different methodologies (spectrophometric using ethanol as solvent, derivative spectrophotometric using sulfuric acid 0,1N as solvent and derivative spectrophotometric using methanol as solvent) in stability tests. Only the methodology with methanol had presented satisfactory results for quantification of HQ in stability tests. The methodologies with ethanol as well with sulfuric acid did not shown efficacy. From methanol methodology the antioxidants systems and the shelf life were evaluated for temperatures of 45°C and 30°C. Alpha lipoic acid promoted better HQ stability than sodium metabissulfite. Sodium metabissulfite was the antioxidant that best kept the initial characteristics of the cream. Shelf life for HQ without antioxidant was 24h, with sodium metabissulfite was 87h and with alpha lipoic acid was 125 h at 45°C. At 30°C it was evaluated only the sample with antioxidant which showed shef life of 72 h.
Descrição
Palavras-chave
Hidroquinona - Tese, Metabissulfito de sódio, Ácido alfa lipóico, Validation of methodology, Hydroquinone, Sodium metabissulfite
Como citar
FARINELLI, Juliane. Avaliação, modificação e validação de metodologia para estudo de estabilidade de hidroquinona em creme. 2008. 98 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Ciências Farmacêuticas, 2008.