Opioids are prescribed for cancer pain. Over the past decade, the annual increase in opioid prescriptions has been accompanied by an increase in opioid-associated deaths. Health care professionals must be proficient in proper dosing, titrating, and monitoring of opioid medications. With the numerous opioid medications and formulations available, an understanding of pharmacokinetic (PK) and pharmacodynamic (PD) concepts is necessary to appropriately individualize opioid-based cancer pain regimens. The purpose of this review is to highlight PK/PD concepts that are clinically relevant to the use of opioids. By way of a cancer pain patient case scenario, PK/PD concepts that are relevant in the initiation, titration, and rotation of an opioid regimen are discussed.