The Development and Application of a Validated Stability Indicating Analytical Method for Vitamin D3

Abstract

With many promising benefits in health continuously being discovered and established, vitamin D3 is rapidly becoming known as the “Drug of the Future”(1). Global deficiency is associated with both skeletal and non-skeletal conditions. Although a large number of products containing vitamin D3 alone and in combination are available commercially, only two such products are registered as medicines in New Zealand. The balance of the marketed products is classified as dietary supplements, the control of which is minimal. With the poor chemical stability of vitamin D3 being well documented there is a need to determine and identify the degradation profile of the drug and its product to ensure the safety and benefit to the consumers. The degradation products of vitamin D3 have not been identified in literature. Evaluating drug stability is a key component in pharmaceutical formulation development. The general aim of this project was to develop a stability indicating method for the quantitative analysis of vitamin D3. The method developed was capable of separating the analyte from other compounds present, including but not limited to degradation products. Possible identification of significant degradation products was an extended requirement of the method developed. The purpose of this study is linked to the need for a stable vitamin D3 formulation. The applicability of the method to available formulations and its ability to assess drug-excipient compatibility is an extension of the aim to confirm the method as being comprehensive. A reverse phase gradient HPLC method was developed which successfully separated all peaks of interest with sufficient resolution. This method was optimized after degradation studies. The optimized method was validated and used to analyse solid dosage formulations of varying types. Degradation products were identified by isomer preparation and comparison. The method was used to assess drug- excipient compatibility to determine suitable excipients for a stable formulation. An isocratic method was also developed for simple assays but not used for degradation studies. Elevated temperatures, ultraviolet radiation and oxygen contribute to the degradation of the vitamin. Vitamin D degrades rapidly in the presence of acid while a basic environment supports its stability. Due to the acidic nature of gastric fluid additional studies relating to dissolution were conducted. The results obtained influenced the choice of excipients required to enhance stability. The validated reverse phase gradient method successfully separated the vitamin from its degradation products in the degradation studies, in formulations and to assess drug-excipient compatibility. It can be adapted to industrial conditions to be used for assays, stability and formulation studies.