| Abstract [eng] |
Master‘s thesis of Augustė Daugėlaitė „Spectroscopic Study of Statin Stability”. Supervisor: doc. dr. Nora Šlekienė. Vilnius University, Faculty of Medicine, Institute of Biomedical Sciences, Pharmacy and Pharmacology Center. Aim of the study: To evaluate the stability changes of statins (atorvastatin, rosuvastatin, and simvastatin) in different pH media using UV-Vis spectroscopy. Objectives: 1. To assess the dependence of atorvastatin absorption changes on different pH media over time. 2. To investigate the dependence of rosuvastatin absorption changes on different pH media over time. 3. To analyse the dependence of simvastatin absorption changes on different pH media over time. 4. To compare the absorption changes of all three statins (atorvastatin, rosuvastatin, and simvastatin) under different pH conditions. Methods: To evaluate statin stability, buffer solutions with different pH values (1.8, 6.8, and 7.4) were prepared using distilled water and analytical-grade reagents. The pH of the solutions was controlled using a calibrated pH meter. Samples were prepared from pharmaceutical tablet formulations of statins, which were crushed, homogenized, and dissolved in the respective media. The prepared solutions were filtered and diluted to obtain concentrations suitable for UV-Vis spectrophotometric analysis. Absorbance measurements were performed using a UV-Vis spectrophotometer. Changes in statin absorbance were monitored at different time intervals (immediately after preparation, and after 1, 3, 6, and 24 hours), with samples stored under identical conditions at room temperature. Results: It was determined that the absorption changes of all investigated statins over time depended on the pH of the medium. The greatest changes in the percentage of remaining atorvastatin after 24 h were observed in the pH 1.8 medium (81.44%), while smaller changes were found in the pH 6.8 (87.92%) and pH 7.4 (85.36%) media. The greatest changes in the percentage of remaining rosuvastatin were observed in the pH 6.8 medium (80.53%), whereas the smallest changes were found in the pH 7.4 medium (91.34%). Simvastatin absorption changes increased with increasing pH. Therefore, the smallest changes in the percentage remaining after 24 h were recorded in the pH 1.8 medium (88.81%), while the most pronounced changes were observed in the pH 7.4 medium (64.77%). Comparison of all investigated statins showed that the smallest absorption changes in the pH 1.8 medium were observed for simvastatin, in the pH 6.8 medium for atorvastatin, and in the pH 7.4 medium for rosuvastatin samples. Conclusions: 1. It was determined that the absorption changes of atorvastatin depended on the pH of the medium. After 24 hours, the percentage remaining in the pH 1.8 medium was approximately 6.5% lower than in the pH 6.8 medium, indicating a more pronounced decrease in atorvastatin absorption in the acidic environment. 2. The obtained results showed that the absorption changes of rosuvastatin depended on the pH of the medium. After 24 hours, the percentage remaining in the pH 1.8 medium was 10.8% lower than in the pH 7.4 medium, indicating smaller absorption changes and potentially greater stability in the alkaline environment. 3. During the study, it was determined that the absorption changes of simvastatin depended on the pH of the medium. After 24 hours, the percentage remaining of simvastatin in the pH 7.4 medium was 24% lower than in the pH 1.8 medium and approximately 11% lower than in the pH 6.8 medium, indicating greater sensitivity of simvastatin to pH changes. 4. The results showed that the three statins behaved differently depending on the pH of the medium. After 24 hours, the smallest absorption changes were observed for simvastatin at pH 1.8, atorvastatin at pH 6.8, and rosuvastatin at pH 7.4. These findings suggest that even drugs from the same pharmacological group can exhibit different absorption stability depending on the pH environment. |
