Parenteral suspensions flocculated

Resuspendability, or the ability to distribute settled particles with a minimum of shaking, is an important characteristic of parenteral suspensions. Stable, flocculated parenteral suspensions that have been undisturbed for long periods of storage time are easily resuspended. 

Typical excipients used in parenteral suspensions include surfactants that are used to stabilise emulsions and suspensions as wetting agents (polysorbate 80, poloxamer), as micelle makers for the preparation of solubilisations and to influence the flocculation and deflocculation behaviour of a dispersed system (carmellose sodium, polyvidone). Paren-terally used surfactants in high concentrations are toxic and may cause venous irritation and occasional thrombophlebitis. However, these high concentrations are not necessary to formulate stable parenteral suspensions. 

Suspensions are coarse dispersions of finely divided solids in a liquid. The solid particles have a mean particle size greater than 0.1 pm in diameter. Pharmaceutical suspensions are administered orally, topically, and parenterally and should avoid the following problems sedimentation, caking, flocculation, and particle growth. Physicochemical principles in the solid/liquid interface will be discussed in this section as they pertain to the preparation of good pharmaceutical suspensions. 

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