Abstract Opioids are effective in acute and cancer pain management and have increasingly been prescribed in chronic non-cancer pain despite concerns regarding long-term use and lack of efficacy. Opioid actions are via G protein coupled receptors, the activation of which leads to a variety of physiological consequences including analgesia. Prescribing opioids requires careful consideration of individual drug pharmacokinetics and pharmacodynamics, their actions across different physiological systems, side effect profiles and patient factors that influence the drug efficacy to ensure the best opioid is prescribed for each patient.