Browsing by Author "Moutinho, Maria Guilhermina"
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- About the effect of eye blinking on drug release from pHEMA-based hydrogels: an in vitro studyPublication . Galante, Raquel; Paradiso, Patrizia; Moutinho, Maria Guilhermina; Fernandes, Ana Isabel; Mata, José; Matos, António; Colaço, Rogério; Saramago, Benilde; Serro, Ana Paula"The development of new ophthalmic drug delivery systems capable of increasing the residence time of drugs in the eye and improve its bioavailability relatively to eyedrops has been object of intense research in recent years. Several studies have shown that drug loaded therapeutic soft contact lenses (SCLs) constitute a promising approach, with several potential advantages as compared with collyria. The main objective of this work is to study the effect of repetitive load and friction cycles caused by the eye blinking, on the drug release from hydrogels used in SCLs which, as far as we know, was never investigated before. Two poly-2-hydroxyethylmethacrylate based hydrogels, pHEMA-T and pHEMA-UV, were used as model materials. Levofloxaxin was chosen as model drug. The hydrogels were fully characterized in what concerns structural and physicochemical properties. PHEMA-UV revealed some superficial porosity and a lower short range order than PHEMA-T. We observe that the load and friction cycles enhanced the drug release from pHEMAUV hydrogels. The application of a simple mathematical model, which takes into account the drug dilution caused by the tear flow, showed that the enhancement of the drug release caused by blinking on this hydrogel may be relevant in in vivo conditions. Conversely, the more sustained drug release from pHEMA-T is not affected by load and friction cycles. The conclusion is that, depending on the physicochemical and microstructural characteristics of the hydrogels, blinking is a factor that may affect the amount of drug delivered to the eye by SCLs and should thus be considered."
- Effect of sterilization on chlorhexidine loaded soft contact lensesPublication . Topete, Ana; Moutinho, Maria Guilhermina; Saramago, Benilde; Serro, Ana Paula
- Vitamin D in food supplements: labeling surveyPublication . Figueiredo, Alexandra; Auxtero, Maria Deolinda; Moutinho, Maria Guilhermina; Neves, Inês; Inez, Raquel; Reis Costa, IsabelAn adequate vitamin D (vitD) intake (Recommended Daily Allowance, RDA= 5μg) is crucial for health maintenance and its deficiency is associated with several health problems. The increase in hypovitaminosis D cases and the proliferation of food supplements (FS) that are easily accessible by the population, have led to an unrestrained chronic consumption of FS. VitD may accumulate in the body and originate toxicity (Tolerable Upper Limit, UL=100 μg). The aim of this study was to evaluate if daily vitD doses mentioned in FS labels are in conformity with RDA. 210 solid and liquid FS (for pediatrics and adults) sold in Portuguese pharmacies, supermarkets, health shops and on the internet were examined for indicated daily intake of vitD and compared to RDA and UL values. 51.43% of FS have values higher than RDA, 8.57% higher than UL. The average vitD daily dose in FS is 24.48 μg, with a high variability between samples (0.25 - 250 μg). Majority of FS labels recommend vitD daily doses above RDA and some even above UL, regardless of being for adults or children. Therefore, it is crucial that vitD dose in FS is reviewed to ensure the safety of these products.