Clindamycin is an antibiotic used for the treatment of bacterial infections. It has a bacteriostatic and mild bactericidal effect. Clindamycin topical solution is used to treat acne.
The purpose of the work was to introduce a simple method that can be used in pharmacies or galenic laboratories for quality control to determine the content of clindamycin hydrochloride in galenic products. We have developed simpler techniques, UV spectrophotometry and titration method. The pharmacopoeial HPLC method was used as a reference method. All three methods were evaluated and shown to give reliable results and then used for comparative analysis of different samples containing clindamycin.
As part of a stability study, we examined the appropriateness of simple methods. Clindamycin hydrochloride was found to be unstable in the alkaline medium at high temperature. Since the concentration of clindamycin hydrochloride is determined via chlorides by the titration method, no instability of the active substance was detected. However, UV spectrophotometry proved to be less accurate for determining the concentration of clindamycin hydrochloride in untsable samples compared to the reference method. Both simpler methods are not suitable for determining of clindamycin hydrochloride content when instability is expected. Clindamycin hydrochloride is stable at room temperature and in the pH range from 3 to 5 for a long period of time.
When determining the content of clindamycin hydrochloride in solutions of two different standards with different purity and in samples prepared according to the recipe (1 % topical solution), all three methods showed comparable results. In the analysis of expired galenic products with clindamycin hydrochloride, comparable results were obtained by HPLC and titration. The results of UV spectrophotometry deviated due to an additional component in the sample, which was confirmed by HPLC. The UV method is not selective and therefore also not suitable for the analysis of samples where interferences are present. By analyzing galenic products with clindamycin hydrochloride from three manufacturers that are within the shelf life, we proved the comparability of all three methods.
Based on the results, it can be concluded that the HPLC method remains the method of choice for determining the content of clindamycin hydrochloride in topical solutions. We suggest the use of simpler methods in the quality control of stable topical products.
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