Determination of ascorbic acid release from microemulsions and evaluation of physicochemical properties
| Date |
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2020-05-08 |
Students section.
eISBN 978-9955-15-646-8.
Bibliogr.: p. 18
Introduction: Microemulsions (ME) — a self-forming dosage form with a stable phase change system (1). The advantage of the ME: formulation for poorly soluble preparations, increased transmembrane bioavailability and protection of the unstable drug (2). Objective: to evaluate ascorbic acid kinetics from ME which depends on excipients, pharmaceutical and ME type. Materials and methods: The active substance is L-ascorbic acid (AA). It belongs to biopharmaceutical class III, is highly soluble but has limited absorption and low membrane permeability (3). ME modeled with cold-pressed flaxseed oil (4). ME compositions: ME1 (o/w) modeled with surfactant tween 20 (86,35%). ME2 (w/o) formed with surfactants (S) tween 80 and span 80 (60%) and cosurfactant (CoS) 1,2-propanediol (2,5%). ME3 (w/o) modeled with surfactants tween 80 and span 80 (50%) and cosurfactant 1,2-propanediol (2,5%) (5,6). AA was 1%. Method – titration. ME stored for 24h, the properties evaluated: partical size (nm), polydispersity index (PDI), pH, viscosity. The effect of excipients and ME type on the pharmaceutical availability of AA was evaluated in an in vitro release study by vertical diffusion cell. Stability assessed after one month. ME stored under natural conditions in the dark, at temperature 15-25°C. Results: Physicochemical properties: pH~6. The viscosity of ME1: 427; ME2 179, ME3 194 mPa•s. ME1, ME2, ME3 partical size: 4973; 2518; 2033; PDI: 0,59; 0,44; 0,26. After 45min., ME3 relaxed 32% of AA, after 4h - 49%. AA content increased steadily. ME2 differs from ME3 in amount of S/CoS mixture. After 45min., ME2 released 31% of AA, after 4h. – 59%. After 45min. ME1 relaxed 17% of AA, after 4h. — 55%. For comparison, 1% aqueous AA solution after 45min. relaxes 49% of AA and after 2h. – 82%. Pharmaceutical form, viscosity and type of ME have a significant influence for the AA release. AA was incorporated in the aqueous phase of ME, i[...].