Osmotic adjustment shock

Tonicity agents are added to injectable preparations to prevent osmotic shock at the site of injection upon administration, and thereby reduce local irritation. Typical excipients used for tonicity adjustment include saline, glycerin, mannitol, dextrose, and trehalose. Tonicity is a colligative property that depends primarily on the number of dissolved particles in solution. Hence, the amount of tonicity agent to be added depends on the specific formulation. Typically, osmolality of 280 to 320mOsm is considered iso-osmotic. 

As would be expected, the combination of thermal and osmotic shocks has been shown to have a large effect on the osmotic strength of anion resins.This is illustrated in Fig. 27, where the decrease is shown to be over 15% in just 150 cycles. The important processing point to remember from this is that if the regeneration of a resin is performed at a temperature more than 20°C different from the temperature of the operating (loading) stream, it is advisable first to adjust the temperature of the resin with distilled water until it is at the temperature of the regenerant. 

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