PURPOSE: To lay the fundamentals of drug-related problems (DRPs) in older adults, and to organize them according to a logical process conciliating medical and pharmaceutical approaches, to better identify the causes and consequences of DRPs. MATERIALS AND METHODS: A narrative overview. RESULTS: The causes of DRPs may be intentional or unintentional. They lie in poor prescription, poor adherence, medication errors (MEs) and substance use disorders (SUD). Poor prescription encompasses sub-optimal or off-label drug choice; this choice is either intentional or unintentional, often within a polypharmacy context and not taking sufficiently into account the patient's clinical condition. Poor adherence is often the consequence of a complicated administration schedule. This review shows that MEs are not the most frequent causes of DRPs. SUD are little studied in older adults and needs to be more investigated because the use of psychoactive substances among older people is frequent. Prescribers, pharmacists, nurses, patients, and caregivers all play a role in different causes of DRPs. The potential deleterious outcomes of DRPs result from adverse drug reactions and therapeutic failures. These can lead to a negative benefit-risk ratio for a given treatment regimen. DISCUSSION/CONCLUSION: Interdisciplinary pharmacotherapy programs show significant clinical impacts in preventing or resolving adverse drug events and, suboptimal responses. New technologies also seem to be interesting solutions to prevent MEs. Better communication between healthcare professionals, patients and their caregivers would ensure greater safety and effectiveness of treatments.< Réduire