There is a high prevalence of pain in older people. Optimal assessment and management of pain in this population is challenging. The pharmacokinetics and pharmacodynamics of analgesic medications are affected by ageing and frailty, as well as by intercurrent medical conditions and their treatments. This review describes what is currently understood about the impacts of old age and frailty on the clinical pharmacology of commonly used analgesics, to provide a rational basis for the use of these medicines. In view of the wide age-related inter-individual variability in pharmacokinetics and pharmacodynamics of analgesic medications, monitoring of clinical response and adverse effects is essential to optimize pain control in older people.