Chapter 3 - Role of Physicochemical Parameters on Drug Absorption and Their Implications in Pharmaceutical Product Development

Abstract

The principal objective of any dosage form is to augment the bioavailability as well as the stability of the drug and its product. The quantity of drug concentration in systemic circulation is one of the imperative factors for exerting any pharmacological activity. The ultimate aim is to avail the higher amount of administered drug in systemic circulation leading to maximum absorption from the gastrointestinal tract. In general, a drug moiety undergoes absorption through various membranes or tissue-barriers including gastrointestinal tract and blood–brain barriers by following several mechanisms such as passive transport, active transport and by using carrier proteins. A number of physicochemical as well as physiological properties of the drugs play a crucial role in determining the rate of drug absorption which in turn greatly affect the rate of onset of drug action. Certain physicochemical properties like solubility, pH of gastrointestinal tract and plasma fluid, partition coefficient, dissociation constant of acid, particle size, surface area, dissolution rate etc. are always taken into primary consideration while designing as well as deciding the dosage form of any drug. To surmount various physicochemical and physiological barriers, a drug can be modified into different forms like prodrugs, clathrates, hydrates, and complex, among which the complexation of a drug with cyclodextrin is found to be one of the most researched drug delivery systems in order to improve the aqueous solubility.