Suspensions possess certain advantages over other dosage forms. Some
drugs are insoluble in all acceptable media and must, therefore, be administered
as a tablet, capsule, or as a suspension. Because of their liquid character,
suspensions represent an ideal dosage form for patients who have difficulty
swallowing tablets or capsules. This factor is of particular importance
in administration of drugs to children. Suspensions of insoluble drugs
may also be used externally, often as protective agents.
In addition, disagreeable tastes can be masked by a suspension of the
drug or a derivative of the drug, an example of the latter being the drug
chloramphenicol palmitate. Finally, drugs in suspension are chemically
more stable than in solution. This is particularly important with certain
antibiotics and the pharmacist is often called on to prepare such a suspension
just prior to the dispensing of the preparation.
Suspensions also possess some disadvantages relative to other dosage
forms. The primary disadvantage is their physical instability; i.e.,
that they tend to settle over time leading to a lack of uniformity of dose.
This can, however, be minimized by careful formulation and by shaking the
suspension before each dose is delivered. An additional disadvantage is
that the texture of suspensions may be unpleasant to patients and should
be carefully considered during formulation.