deflocculation

Picture marbles poured one by one into a jar: each settles independently and they nest together into a dense, tightly packed pile. Deflocculated particles do the same. Because they carry a strong like charge they repel each other and stay as separate individual units, never clumping together while suspended.

At first this looks ideal — a deflocculated suspension stays uniformly cloudy for a long time, since individual fine particles settle slowly. But there is a hidden trap: when the separate particles eventually do reach the bottom, they pack tightly with no liquid trapped between them and gradually consolidate into a dense, compact sediment called a cake.

That cake is the problem. The closely packed particles are held together strongly enough that ordinary shaking will not break them apart, so the dose cannot be redispersed uniformly and the patient may pour off clear liquid leaving drug behind. For this reason a hard-caking deflocculated suspension is generally undesirable, and formulators usually prefer controlled flocculation instead.