Solid dosage forms active ingredients

Johnson MCR. Particle size distribution of the active ingredient for solid dosage forms of low dosage. Pharma Acta Helv 1972 47 546-559. 

Most oral preparations are solid dosage forms that need to be dissolved before they can be absorbed. The inert ingredients of such dosage forms can have a profound effect on the dissolution of the active ingredient and thereby control its rate of absorption. In addition, the drug may be unstable in the gastrointestinal fluids, as in the case of penicillin G, or metabolized. 

The validation process of a solid dosage form begins with a validation of the raw materials, both active pharmaceutical ingredients (APIs) and excipients [16-19],... 

Although excipients are the non-active ingredients, they are indispensable for the successful production of acceptable solid dosage forms. The important roles played by excipients in tablets and capsules, freeze-dried, and spray-dried powders, as well as powder aerosol formulations, were discussed. Some recent applications of excipients in controlled, release formulations for biologicals were also highlighted. Finally, incompatibility problems attributable to excipients were considered with an emphasis on the indirect role of excipients through moisture distribution. 

In addition to the active ingredient, solid dosage forms usually contain one or more excipients. In such powder... 

Aldehydes, even in trace amounts, are often found to adversely affect the stability and efficacy of drugs via direct reaction with the active pharmaceutical ingredient (API). Formaldehyde, acetaldehyde, furfural, and glyoxal are the aldehydes most often responsible for stability issues in drug products. In solid dosage forms, these aldehydes are sufficiently small to be mobile enough to react effectively with APIs. 

The BCS is a scientific framework for classifying active pharmaceutical ingredients based upon their aqueous solubility and intestinal permeabihty. When combined with the dissolution of the pharmaceutical product, the BCS takes into account three major factors that govern the rate and extent of drug absorption (exposure) from immediate-release oral solid dosage forms dissolution, solubility, and intestinal permeability. 

A special consideration for a formulation and its stability is the effect of water. Carstensen provides a good discussion of the effect of water on solid dosage forms. The effect of water can be a problem in a formulation when the active ingredient is moisture sensitive. When water affects the formulation and causes... 

---