ABSTRACT
In the rational design and evaluation of dosage forms for drugs, the stability of the active components must be a major criterion in determining their suitability. Several forms of instability can lead to the rejection of a drug product. First, there may be chemical degradation of the active drug, leading to a substantial lowering of the quantity of the therapeutic agent in the dosage form. Many drugs (e.g., 5-fluorouracil, carbamazepine, digoxin, and theophylline) have narrow therapeutic indices, and they need to be carefully titrated in individual patients so that serum levels are neither too high as to be potentially toxic nor too low as to be ineffective. In these cases it is of paramount importance that the dosage form reproducibly deliver the same amount of drug.
