Evaluation of vihicle's effect on salicylic acid release in vitro from semi-solid preparations

Objective of work: to evaluate quality of salicylic acid ointments manufactured by pharmacies by assessing release of salicylic acid in vitro and suggest alternative composition and technique semi- solid preparation, characterized by the same or better release of salicylic acid. Main tasks: 1. To select and adapt a suitable method for quantity analysis for salicylic acid; 2. To select appropriate conditions for salicylic acid release in vitro from semi- solid preparation; 3. To research release of salicylic acid in vitro from semi-solid preparations made by Lithuanian pharmacies; 4. To formulate semi- solid preparations containing salicylic acid and evaluate quality; 5. To research release of salicylic acid in vitro from formulated semi- solid preparations and compare release results with release results of semi- solid preparations made by Lithuanian pharmacies. Methods: release of salicylic acid from semi- solid preparations executed by using modificated vertical diffusion Franz cells. The quantity analysis executed by using spectrophotometric methods. UV- Vis spectrophotometer Agilent 8453, wavelength 296 nm, calibration curve within 0,005- 0,03 mg/ml. Ointments quality evaluated by pH and dynamic viscosity. Results: after 4 h 5 % salicylic acid ointments released salicylic acid: LSMU pharmacy‘s ointment- 3,36 %, “Ąžuolyno” pharmacy‘s ointment- 2,54 %, UAB “VJV“ ointment- 2,71 %, experimental ointment- 1,89 %; ointments made by mixing in mortar with glycerol- 2,27 %, 1,2-propanediol- 3,43 %, polyethelene glycol 400- 4,04 %; ointments made by mixing in mortar and automatic mixer with glycerol- 2,29 %, 1,2-propanediol- 3,50 %, polyethelene glycol 400- 4,24 %; ointments made by mixing in mortar and automatic mixer, before that vaseline was molten, with glycerol- 2,73 %; 1,2-propanediol- 3,64 %; polyethelene glycol 400- 4,92 %. Conclusions: 1. Selected and adapted a suitable UV spectrophotometric method for quantity analysis for salicylic acid. The method was sufficiently accurate. 2. 2 % polysorbate 80 solution was selected as appropriate acceptor medium. 3. There was approved different salicylic acid release from ointments made by Lithuanian pharmacies. The most salicylic acid released from LSMU pharmacie‘s ointment. 4. Based on scientific literature were developed ointments containing salicylic acid and their quality were evaluated. Formulated ointments pH was acidic (≤3,06), dynamic viscosity 6,21-7,19 Pa•s. 5. Release of salicylic acid in vitro from semi- solid preparations made by pharmacies and formulated in laboratory was evaluated. The greatest share of salicylic acid among oitments was released by ointment made by dissolving salicylic acid in 10 % polyethelene glycol 400 and inserting this into molten vaseline by mixing in mortar and automatic mixer. Ointment made in this way release salicylic acid 1,5 times more than ointment made by LSMU pharmacy