The importance of reporting unexpected drug failure

Unexpected drug failure is a lack of therapeutic effect, which is not expected based on the characteristics of the drug and patient. Essentially, it may occur either for interactions (with other drugs or foods) or for biopharmaceutical issues. The risk arising from interactions is generally well characterised and physicians are well aware of it, and the importance of reporting cases of failure due to interactions is obvious. Less is known about the mechanisms and potential risk deriving from biopharmaceutical problems, and we will therefore focus on this issue. Biopharmaceutics describes the influence of the physical/chemical properties of the drug and drug product on the rate and extent of systemic drug absorption. Because after oral administration of solid pharmaceutical forms drugs must dissolve in gastrointestinal fluids before being absorbed through the intestinal epithelium, biopharmaceutical problems essentially arise from an insufficient dissolution performance. A typical situation where an insufficient dissolution may cause unexpected drug failure is when a patient is switched from one drug product to a different product. Different drug products with the same active substance may differ in manufacture and excipient composition.