Define Suspensions. Give their advantages.

 Definition of suspension

     Suspension are characterized as biphasic [heterogenous system] liquid dosage forms in which finely divided drug particles [dispersed phase] are suspended uniformly in a liquid vehicle [continuous phase].

      Solid particles represent the undissolved or immiscible agents with their size ranging from 0.5-5µ (usually less than 10µ). These solid particles are also referred as the dispersed phase or internal phase. They are usually suspended in the vehicle or continuous phase with the help of one or more suspending agents. 

      Water is the most commonly used solvent in the preparation of oral suspension.

suspensions are usually used for oral, parenteral or topical application. 

      Depending upon the size of the dispersed phase, suspension may be termed as  coarse [1nm to 0.5µm size] or colloidal[10-50µm].

      Moreover, suspension containing 2-10% w/v of solid particles as   dilute suspensions whereas those about 50% w/v solid particles are known as concentrated suspensions.

      The most important parameter concerning the suspension is the particle size of the dispersed phase.

      Suspension meant for topical application onto the skin should contain finely divided solid particles.

      Particles size of dispersed phase which are meant for parenteral administration should pass via the needle. 

      Moreover , suspension meant for ocular usage should also contain finely divided dispersed phase to avoid any pain or discomfort to the patient 

Advantages / Merits Of Suspensions

      1. Suspension  enhance the stability of chemically unstable drugs like Procaine Penicillin G.

      2. Bioavailability of drugs formulated as suspension is greater than that of other oral dosage forms. Coated tablets < Compressed tablets <Capsules <Suspensions.