Drug Solubility: Importance and Enhancement Techniques

TLDR

Solubility determines the achievable drug concentration in systemic circulation, yet over 40 % of new chemical entities are practically insoluble, posing a major challenge for formulation scientists because a drug must be present as a solution at its absorption site. Solubility can be enhanced by physical and chemical modifications such as particle size reduction, crystal engineering, salt formation, solid dispersion, surfactants, and complexation, with the choice guided by drug properties, absorption site, and dosage‑form requirements.

Abstract

Solubility, the phenomenon of dissolution of solute in solvent to give a homogenous system, is one of the important parameters to achieve desired concentration of drug in systemic circulation for desired (anticipated) pharmacological response. Low aqueous solubility is the major problem encountered with formulation development of new chemical entities as well as for the generic development. More than 40% NCEs (new chemical entities) developed in pharmaceutical industry are practically insoluble in water. Solubility is a major challenge for formulation scientist. Any drug to be absorbed must be present in the form of solution at the site of absorption. Various techniques are used for the enhancement of the solubility of poorly soluble drugs which include physical and chemical modifications of drug and other methods like particle size reduction, crystal engineering, salt formation, solid dispersion, use of surfactant, complexation, and so forth. Selection of solubility improving method depends on drug property, site of absorption, and required dosage form characteristics.