Earlier the subject of powders was addressed from a physicochemical stand-point.
Solid Dosage Forms
INTRODUCTION
Earlier
the subject of powders was addressed from a physicochemical stand-point. The
unit processes involved in incorporating powders in solid dosage forms must
also be considered. Solid dosage forms can be divided into granules, capsules,
tablets for oral delivery, and inhalation products. Note that solid
particulates might also play a role in certain parenterals in the form of
recon-stitutable products.
Solid
dosage forms are the most desirable final products of a development process
that begins with drug discovery and proceeds through bulk product
manufacturing, preformulation, and formulation characterization to one of the
products mentioned. Figure 14.1 illustrates an abbreviated sequence of steps through
which the drug passes to the final dosage form.
Most
solid dosage forms are intended for oral ingestion. The drug released from the
dosage form is available at the site of absorption or action within the
gastrointestinal tract.
Preformulation
studies are required before a formulation is developed. By studying the
properties of the drug, it is possible to delineate a course of action for
composing the formulation. The properties studied are
·
organoleptic properties,
·
purity,
·
particle size, shape, and surface area,
·
solubility,
·
dissolution,
·
parameters affecting absorption (dissociation constant,
partition coefficient),
·
crystal properties and polymorphism,
·
stability (chemical and physical),
·
compatibility (with excipients and potential packaging
materials), and
·
miscellaneous physicochemical properties like
density,
hygroscopicity,
flowability,
compressibility,
and
wettability.
Problem
solving in service of formulation development can be derived from knowledge of
these properties. Each item has been covered in depth elsewhere and is beyond
the scope of this volume.
The
additives employed in solid dosage forms are categorized as diluent, glidant,
lubricant, disintegrant, and binder. Several candidates from each cate-gory may
be considered as components of a possible dosage form. Lubricants and
disintegrants play a more substantial role in compressed tablet dosage forms
than they do in granules or capsules. This will be discussed in more detail
later.
FIGURE 14.1 Drug to the final dosage form.
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