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  • Drug-Excipient Compatibility Study

    What is drug-excipient compatibility?

    Drug-excipient compatibility study is a very much important stage of formulation development of drug products in combination with excipients. It’s a significant phase of the pre-formulation study. Drug product not only contains active pharmaceutical ingredient (API) but it’s a combination of different forms of excipients. it’s important to study the physical and chemical interaction between API and excipient. Generally, for excipient compatibility study combination of binary mixes in the ratio of 1:1 is assessed. In some instances, to check the extreme interaction and complications, multiple excipient mixtures in presence of API were appraised.

    Importance of excipients and their compatibility with API:

    Selection of appropriate excipients could be done by performing the drug excipient compatibility study. It supports preventing the expected last-minute complications throughout the process of formulation development.

    The role of excipients is important in the formulation development of active ingredients into an effective drug product. Excipients enhance the essential quality of the drug product such as the exact required dosage, stability, solubility, performance, acceptability, quality, absorption of the drug in vivo, safety, and efficacy. As per regulatory requirements, a drug-excipient compatibility study requires to predict probable degradation pathways of the drug product. This study supports to recognition of the selection of appropriate excipients and helps to understand the interaction between drugs and excipients and the storage condition of the product.

    Interaction of drug excipients:

    Drug-excipient compatibility complications obtain from the direct reactions between API and excipients or by the presence of responsible impurities in the excipients. Interaction between excipients and the presence of a sensitive functional group of API results in the incompatibility of drug-excipients compatibility study. Degradation of the drug in presence of excipients leads to the formation of impurities and identifying these impurities needs a complete understanding of the reaction and sufficient analytical details. Analytical characterization data helps to understand the possible degradation pathway of API.  

    Following are some of the typical processes of drug-excipient compatibility which may impact the drug product stability in presence of an excipient.

    1. Physical interactions,
    2. Chemical interactions,
    3. Physiological interactions,

    Analytical techniques for the analysis of drug-excipient compatibility samples:

    Following are the details of the analytical technique used for the analysis of drug excipient compatibility samples:

    1. HPLC-High Pressure Liquid Chromatography,
    2. Differential Scanning Calorimetry.
    3. Fourier-transform infrared spectroscopy,
    4. X-ray powder diffraction instrument,
    5. Thin Layer Chromatography,
    6. Osmometry,
    7. Vapor Sorption Analysis,
    8. LC mass spectrophotometer,
    9. Nuclear magnetic resonance etc.

    Drug-excipient compatibility is a key stage for the development of a well-planned, robust, safe, stable, and bio-available drug product. It helps to understand the selections of suitable excipients, appropriate formulation composition, proper primary packaging material, and suitable storage conditions of the drug products. Selection of appropriate excipients and evaluation of probably unsuitable excipients during the pre-formulation studies is mainly to achieve the target product profile (TPP) and critical quality attributes (CQA).  


    1. ICH Q1A (R2) (2000) Stability Testing of New Drug Substances and Products,
    2. ICH Guideline Q3A (R) (2002) Impurities in New Drug Substances,
    3. Baertschi, S.W., Alsante, K.M. and Reed, R.A. (2011) Pharmaceutical Stress Testing: Predicting Drug Degradation.2nd Edition, Informa Health Care,
    4. Chaurasia G. (2016). A Review on Pharmaceutical Preformulation Studies in Formulation and Development of New Drug Molecules. International Journal of Pharmaceutical Science and research,
    5. Crowley and Martini, P. Crowley, L.G. Martini Drug-excipient interactions, Pharmacy Technology.

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