Abstract

Parenteral formulations, both large and small volume, have been discussed in depth in Volume II of the Encyclopedia of Pharmaceutical Technology (V II, pp. 884–897, Dosage Forms: Parenterals). However, no discussion of parenteral formulations can be complete without an adequate description of “Tonicity”. Tonicity is an important factor in the formulations of products intended for application to sensitive mucous membranes of organs such as eye, ear, and nose. In this chapter, an attempt will be made to first introduce tonicity with respect to its physiological significance, followed by a discussion of the physicochemical basis for tonicity and colligative properties. This will be followed by a brief review of methods of measuring and/or calculating tonicity and the established methods of adjusting tonicity and the examples illustrating each of the methods. Tables listing the established values necessary to do the calculations will be provided at the end of the chapter. Excellent comprehensive reviews dealing with various aspects of tonicity are available in literature in the form of chapters in various textbooks for pharmacy students (Remington’s Pharmaceutical Sciences, Martin’s Physical Pharmacy, etc). A list of such reading material is provided at the end of the chapter in bibliography for interested readers to find more details.