Preformulation stage excipient compatibility

In conclusion, drug-excipient compatibility studies have a key role at the early preformulation stages to select excipients or after formulation to help identify the mechanism of any detected instability [14], An understanding of the potential physicochemical interactions of drug with known chemical reactivities of excipients and... 

Moreover, if adequate forced degradation studies (i.e., acid/base hydrolysis) are performed in the early preformulation stage, the identification of a potential degradation product that might arise during excipient compatibility... 

During the preformulation and formulation stages of a parenteral dosage form, the physicochemical properties and excipient compatibility of the pharmaceutical active ingredient (API) should be thoroughly evaluated. The test method requirements are similar to those for oral dosage forms. 

Although there has been some debate in the literature about the nature of compatibility testing and the value of results (e.g., see Monkhouse and Maderich 1989, and Monkhouse 1993), it is felt that it still has some relevance to pharmaceutical preformulation. Essentially, there are four major stages in drug-excipient compatibility studies, but before considering such studies, it is worth checking whether there are any known incompatibilities, as is shown in Table 6.17 (Monkhouse 1993). 

At the early stages of optimisation, preformulation studies are usually conducted to screen excipients or packaging materials and to select those compatible with the candidate drug, using accelerated stress testing procedures. More details about the preformulation techniques, which can be employed for compatibility studies, are discussed in Chapter 3. The importance of doing compatibility studies is for reducing the number of excipients and formulation options to test in further product optimisation studies. 

Before process validation can be started, manufacturing equipment and control instruments, as well as the formulation, must be qualified. The formulation of a pharmaceutical product should be studied in detail and qualified at the development stage, i.e., before the application for the marketing authorization is submitted. This involves preformulation studies, studies on the compatibility of active ingredients and excipients, and of final drug product and packaging material, stability studies, etc. 

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