Stability evaluation of an extemporaneously compounded carbimazole oral suspension.

Aims: To examine the physical, chemical and microbiological stability characteristics of an extemporaneously compounded carbimazole 2 mg/mL oral suspension. Methods and Results: To determine the chemical stability of carbimazole in oral suspension, an analytical method was developed with high‐performance liquid chromatography (HPLC) that achieved a good resolution of the analysis. The physical and chemical stability studies of the drug were conducted at four different storage conditions: 4°C, 25°C, 4°C in‐use (to simulate a patient daily use condition), and 7 days at 4°C and 3 days at 25°C (to simulate a condition in which a patient does not return the medication back into the refrigerator after use). The microbiological test was performed on the "4°C in‐use" storage condition. The preparations were found to be physically and microbiologically stable since there were no significant changes in colour, odour, dispersion and microbial contamination tests. Regarding chemical stability, samples stored at 4°C and 25°C maintained more than 90% drug recovery limit for up to 3 weeks and 3 days, respectively. There were no significant changes in pH value for up to 6 weeks. Conclusion: A shelf life of up to 19 days at 4°C, based on the 95% lower confidence interval (CI) of the data obtained, and 2 days at room temperature can be recommended for carbimazole oral suspension. [ABSTRACT FROM AUTHOR]