Kojic acid (5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) is an organic acid derived from the fermentation of fungi of diverse genus such as Aspergillus and Penicillium, 1 and it was first isolated in 1907. 2,3 Its most common use is as a skin depigmenting agent, attributed mainly to the inhibition of tyrosinase, which is the key enzyme in melanin synthesis. Leucocyte modulation, copper-chelating action and free radical scavenging are also involved in kojic acid depigmenting mechanism. Besides that, antioxidant, antibacterial and anti-inflammatory activities were also reported. 4 There have been reports of antimicrobial and toxicity studies since the forties, 2 but mechanisms of action have not yet been fully elucidated.Among the disadvantages of this molecule, one can mention the possibility of causing contact dermatitis, sensitization, redness and erythema. 5 Kojic acid also has low stability, being sensitive to light
The objective of this study was to evaluate quality parameters of magistral topical solutions containing minoxidil (A, B and C), comparing the results with the ones obtained for the industrial formulation. Organoleptic tests, evaluation of the pH and density, centrifuge test, drug content determination, comparison of indicated dosages and in vitro follicular penetration of minoxidil were performed. Regarding the organoleptic properties, differences in color and viscosity were observed between the magistral (composed of minoxidil sulfate) and the industrial formulations (composed of minoxidil base). For pH values, the magistral solutions presented considerably more acidic pH, compared to the industrial sample. For the density test, the samples with the highest ethanol percentages (B and C) presented lower density. In the centrifuge test, none of the samples showed changes. Considering the drug content test, only the industrial sample and the magistral sample C showed drug percentage within the expected (90-110%), indicating lack of correction factor determination by the magistral pharmacies. Furthermore, it was observed that the dosage indicated by the magistral pharmacies do not correspond to the dose indicated by the industry, being significantly lower. All topical solutions tested presented hair follicle penetration of minoxildil, without statistical difference. The results indicate that there is a failure in the magistral pharmacies regarding the production and the indication of dosage of minoxidil topical solutions.
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