Drug safety and efficacy impaired by quality failure

The three main pillars of drug evaluation are quality, safety and efficacy. Each marketing authorization dossier has to demonstrate conformity with quality, safety and efficacy requirements separately. While this is justifiable, it may nevertheless lead to some important problems being overlooked. The relationship between these three aspects of a medicinal product can be of great importance. Little is said about how quality can affect safety or even efficacy. It is worth discussing these connections in order to assess side-effects appropriately and to distinguish between quality failures and real pharmacovigilance problems. Not every side-effect is a result of the drug's pharmacodynamic or pharmacokinetic properties or other therapy-related issues such as interactions. Sometimes a patient complaint is caused by substandard quality of the drug. This possibility should never be ignored in any assessment of side-effects. This paper presents a useful check-list of quality failures that can endanger drug safety.