Citric Acid: A Multifunctional Pharmaceutical Excipient

Citric acid, a tricarboxylic acid, has found wide application in the chemical and pharmaceutical industry due to its biocompatibility, versatility, and green, environmentally friendly chemistry. This review emphasizes the pharmaceutical uses of citric acid as a strategic ingredient in drug formulation while focusing on the impact of its physicochemical properties. The functionality of citric acid is due to its three carboxylic groups and one hydroxyl group. These allow it to be used in many ways, including its ability to be used as a crosslinker to form biodegradable polymers and as a co-former in co-amorphous and co-crystal applications. This paper also analyzes the effect of citric acid in physiological processes and how this effect can be used to enhance the attributes of pharmaceutical preparations, as well as providing a critical discussion on the issues that may arise out of the presence of citric acid in formulations.

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About this article: Lambros, M.; Tran, T.; Fei, Q.; Nicolaou, M. Citric Acid: A Multifunctional Pharmaceutical Excipient. Pharmaceutics 2022, 14, 972. https://doi.org/10.3390/pharmaceutics14050972

In the article you find Chapters on the following citric acid usages besides others:

• Citric Acid in Taste-Masking and Effervescence

• Citric Acid in the Lyophilization Process

• Citric Acid in Polymers

• Co-Amorphous Drugs and Co-Crystals

Conclusions
Citric acid is an important excipient in many types of pharmaceutical formulations. Its three carboxylic groups and one hydroxyl group provide the functionality and versatility required for its many applications. In this review, we have discussed the fundamental strategies that take advantage of its functionality and have summarized its uses in pharmaceutical formulations. The presence of citric acid in formulations solves many problems but also causes some challenges. Understanding the physicochemical interactions of citric acid with the active pharmaceutical ingredients and other excipients in formulations will promote rational formulation design and effective therapeutics.