Yes it is necessary to check the compatibility of API with excipients. first step of preformulation study where confirm compatibility of API with excipients to get information about compatability as well as effective ratio of excipients with API.

Thanks Anita for your response. I am not a ceutics person, so your feedback is important. I agree compatibility of excipients with the API is necessary. However, when a formulation is subjected to a stability study and the API is found stable; it means the API does not get physicochemically modified. Is it sufficient to assume excipient compatibility?

There are two planes to this question. On one plane are the regulations governing the necessary and sufficient tests for such a case. All these documents are based on GMP and GLP, but there are differences and peculiarities in different countries.

The second plane is the actual informativeness of your study. In this case, the answer to your question depends on how selective your chosen method of analysing AFI is, whether you cannot get false positive results due to the fact that you take into account not only unchanged AFI, but also its closely related compounds that have formed in the dosage form as a result of interactions. In addition, you should analyse the stability study method: how well do the accelerated ageing conditions mimic the natural storage conditions of the drug? Are the time and conditions of the experiment sufficient to show possible interactions?

Thanks, Sepp, for the insights and valuable suggestions. will consider your points.

The formulation should be started after confirming its compatibility which stands acceptable till expiry date