| Abstract: | Lidocaine is widely accepted local anesthetic, which is applied in the form of freely soluble hydrochloride salt. In this study we evaluated the pH of respective solutions of lidocaine hydrochloride with ionic polymer - polyacrylic acid or non-ionic polymer - methylcellulose, and compared to physiological skin conditions in the range between 22°C and 41°C. In microscopic observation of lidocaine hydrochloride preparations with polyacrylic acid the micro-sedimentation was revealed, however obtained mixture was opalescent, and homogenously dispersed in aqueous environment. The pH was maintained on the level not higher then 4,0 in the period of 12 hours for polyacrylic acid formulation, whereas in the case of preparation with methylcellulose, the pH increased from acceptable pH of ca. 4,5 to the level of above 6,0. The polyacrylic acid derivatives should be further studiedas vehicles forming preparations with stable pH value during application on the skin, with more specific methods including pH microelectrodes, sufficient for assessments in small quantities of liquids of skin surface. |
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