Impact of excipient interactions on solid dosage form stability.

Area of Science:

• Pharmaceutical Sciences
• Physical Chemistry
• Drug Development

Background:

• Drug-excipient interactions in solid dosage forms can lead to physical changes (e.g., organoleptic properties, dissolution) and chemical degradation.
• Distinguishing between direct drug-excipient interactions and those involving excipient impurities is a recent advancement in understanding chemical instability.
• Common mechanistic themes, such as the role of water and microenvironmental pH, are critical in multiple drug degradation pathways.

Purpose of the Study:

• To review the mechanistic basis of known drug-excipient interactions with case studies.
• To provide an overview of common underlying themes in drug degradation within solid dosage forms.
• To discuss emerging aspects impacting prospective stability assessment methodologies in the pharmaceutical industry.

Main Methods:

• Review of existing literature on drug-excipient interactions and chemical instability in solid dosage forms.
• Analysis of common mechanistic themes, including the role of water and microenvironmental pH.
• Discussion of case studies illustrating drug-excipient interactions and degradation pathways.

Main Results:

• Identified common mechanistic themes in drug degradation pathways, emphasizing the roles of water and microenvironmental pH.
• Highlighted the complexity introduced by solid-state reactions with excipients and/or excipient impurities.
• Underscored the impact of recent developments in understanding degradation pathways on stability assessment methodologies.

Conclusions:

• Understanding drug-excipient interactions is vital for predicting and ensuring drug product stability.
• Emerging paradigms in accelerated stability testing and mathematical modeling offer improved prospective stability assessment.
• Limitations in current drug-excipient compatibility studies necessitate advancements in stability testing and prediction methodologies.