ABSTRACT
Evaluating the dissolution of a candidate molecule for an active
pharmaceutical ingredient (API) before it is developed into a
medicinal product has proven to be fundamental in the development
of solid dosage forms for oral use that contain poorly soluble drugs
(classes II and IV of the Biopharmaceutics Classification System
[BCS]), since in these cases, dissolution is considered to be a limiting
step in absorption.1,2
In the current scenario, the majority of molecules that are now
available or under development present this characteristic and tests
that enable to predict the release of the active substance can provide
valuable data, facilitating the work of formulators, directly resulting
in economy of resources and reduction in the time required to
launching newmedicinal products.3−5
Among the tests available, intrinsic dissolution enables the
dissolution analysis of a pure drug, in a similar fashion to a
conventional test. Accordingly, an apparatus that maintains a
constant surface area of the drug exposed to the medium must be
used, since, contrary to solubility, intrinsic dissolution is not related
to equilibrium, but rather the speed with which the drug is released
from the matrix to the dissolution medium.6,7
Intrinsic dissolution has been used for many years to charac-
terize APIs, especially in preformulation studies, and it is especially
useful because of the small quantity of sample that is necessary to
conduct the tests, as well as the fact that it may be applied both in
the stages prior to development (more precisely, in the prospection
of new chemical entities), the selection of raw material at the
preformulation stage and in the routine analysis of raw material in
a quality assurance laboratory.4,8 Table 4.1 lists some examples of
intrinsic dissolution applications.
