A microemulsion for the cutaneous release of quercetin was prepared. An aqueous phase, containing 40% Transcutol® P as solubilizing agent and permeation enhancer, was emulsified with Labrafil® as oil phase and Labrasol®/Capryol™ 90 as Solvent/Co-solvent. Quercetin was dissolved in the microemulsion at the concentration of 1%. Ternary phase diagrams were generated to determine the optimal concentration of each excipient composing the microemulsion. The physicochemical properties of the microemulsion, such as pH, viscosity, refractive index, and particle size distribution were determined. The microemulsion was stable for 12 months at the storing conditions of 25.0 ± 1.0°C. The in vitro quercetin permeability into and through the abdominal hairless pig skin was determined by vertical Franz's cells. Quercetin showed hardly any permeability through the skin when dissolved in water- and Transcutol® P-free media, whereas a remarkable increase in cutaneous permeability was observed when quercetin was formulated in the microemulsion or when simply dissolved in Transcutol® P. These two last formulations are those showing the lower skin retention.
The objective of this study is to select very simple and well-known laboratory scale methods able to reduce particle size of indomethacin until the nanometric scale. The effect on the crystalline form and the dissolution behavior of the different samples was deliberately evaluated in absence of any surfactants as stabilizers. Nanocrystals of indomethacin (native crystals are in the c form) (IDM) were obtained by three laboratory scale methods: A (Batch A: crystallization by solvent evaporation in a nano-spray dryer), B (Batch B-15 and B-30: wet milling and lyophilization), and C (Batch C-20-N and C-40-N: Cryo-milling in the presence of liquid nitrogen). Nanocrystals obtained by the method A (Batch A) crystallized into a mixture of a and c polymorphic forms. IDM obtained by the two other methods remained in the c form and a different attitude to the crystallinity decrease were observed, with a more considerable decrease in crystalline degree for IDM milled for 40 min in the presence of liquid nitrogen. The intrinsic dissolution rate (IDR) revealed a higher dissolution rate for Batches A and C-40-N, due to the higher IDR of a form than c form for the Batch A, and the lower crystallinity degree for both the Batches A and C-40-N. These factors, as well as the decrease in particle size, influenced the IDM dissolution rate from the particle samples. Modifications in the solid physical state that may occur using different particle size reduction treatments have to be taken into consideration during the scale up and industrial development of new solid dosage forms
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