Solid Dosage Forms

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.