The influence of storage conditions on the stability of selected veterinary drugs in Khartoum state, Sudan

Abstract

In this study the stability of Albendazole oral suspension and Oxytetracycline HCl 5% injection, common in use in veterinary medicine was investigated according to International Cooperation on Harmonization (ICH) guidelines. The objective of the study was to determine the stability parameters (pH, colour and assay percentage) of Albendazole and Oxytetracycline HCl; stored at two different storage conditions as well as to assay their in-use stability. At the beginning to test the study hypothesis, almost all the commercial products of Albendazole (17) and Oxyctetracycline (32) available at the market were collected. The products were tested for pH and colour stability. For oxytetracycline, six samples out of 32 were not stable after measuring the pH value. From photos and manufacturers labeling we could observe that, the colour of some products were unstable. For Albendazole, out of the 17 albendazole commercial products evaluated 7 showed pH values exceeding the recommended values of the manufacturers. Albendazole commercial products available in the Sudanese markets harbour different colour ranging from white, yellow, blue and green. So we are unable to state whether there were change in colour or not. For in use stability testing, two different commercial products each of albendazole and oxytetracycline belonging to two different manufacturers were selected. From each product two patches were examined. The products were stored in controlled storage condition with adjusted temperature and humidity. The products were subjected to in use stability testing i. e. opening the products and drawing samples at certain time points mimicking the manufacturer recommendations for 60 days (albendazole) and 7 days (oxytetracycline). 14 The degradation process, if any, was monitored by an HPLC method. The change in colour using visual inspection and pH value using pH meter, was also monitored. The colour of Albendazole suspension in the two products tested did not show any change during the storage period (60 days). The first product was a yellow or straw yellow suspension and the second one was almost white to yellowish suspension and continued to be like that for the three time points of the test. The pH values of the four tested samples, showed minor to prominent changes in their values with time but they are still within the recommended values. The assay concentration% of the four tested samples, also exhibited prominent deterioration below the recommended level. There is no change in colour of oxytetracycline (An amber clear liquid) samples tested. The pH values of the four tested samples were within the same value of time zero with no change during the 7 days of the study. The four tested compounds showed minor to moderate changes in the active ingredient concentration at day seven following withdrawal of the first sample For real time stability testing the experimental drugs were stored in two different stores. The first one (A) is equipped with controlled temperature and humidity control systems. The second one (B) was a veterinary pharmacy selected randomly from East Nile locality. The temperature and humidity in the stores A and B were monitored and recorded daily using hygrometer for I year. At the beginning of the study all products were proved to be compatible with the recommendations of the manufacturers. There was no change in the colour of albendazole during the nine months at both stores. The pH values in the first store expressed noticeable reduction, although it is still within the recommended range. Following nine months storage the drug content was reduced below the recommended level. 15 In the second store (B), there was no change in the colour of both albendazole products tested. There was considerable change in pH level during the nine month storage, but still it is within the recommended level. The active concentration (assay %), of albendazole fell below the recommended level following storage for nine months. In the first store (A), the two oxytetracycline products expressed no change in colour, and there was slight reduction in pH level (but still within the recommended level) within the six months storage period. The experiment was terminated just after six months due to the reduction of the active concentration (assay %) below the recommended level. In the second store (B), there is only change in the colour in one of the products following six months storage. pH level also here expressed moderate reduction, but still in the recommended range. The active concentration (assay %), of oxytetracycline expressed prominent reduction following storage for six months. The obtained results are of interest for stability studies and/or quality control purposes of Albendazole and Oxytetracycline commercial products. The study concluded that, the selected veterinary drugs evaluated here (albendazole and oxytetracycline) proved to be unstable under stressing environmental conditions in veterinary pharmacies in Khartoum state, Sudan. For improving the shelf-life of both drugs, monitoring of temperature and humidity with veterinary dispensers is highly recommended. Standard operation procedures (SOPs) are of good benefit for the same recommendations.