About Citric acid Weak organic carboxylic acid, an alkalinizing agent, expectorant, antioxidant, flavouring agent. Mechanism of Action of Citric acid Citric acid is an organic acid which is used widely in medicine and also as flavouring agent. Citric acid is an alkalinizing agent which is used to make the urine more alkaline (less acidic).It prevents certain kinds of kidney stones. It is used in expectorant preparations to increase bronchial secretion. It also posses antioxidant properties.