Definition of isotonicity

The clinical importance of all of this is to ensure that the isotonic or iso-osmotic solution does not damage tissue or cause pain when administered. Solutions that contain less particles and pour osmotic pressure below 0.9% are called hypotonic and solutions that contain high osmotic pressure are called hypertonic.

Painful tissue inflammation occurs, upon administration of a hypotonic solution, when water passes through the site of administration through blood cells or tissue. As the water is drawn from the biological cells in an attempt to dilute the hypertonic solution, it shrinks the tissues. The effects of administering a hypotonic solution are usually more severe than the hypertonic solution because the ruptured cells cannot be repaired. Various methods are used to adjust the isotonicity of the pharmaceutical solution. The sodium chloride equivalent method is one of the most widely used methods.