Patients with moderate-to-severe malignancy-related pain require opioid pharmacotherapy. Many cancer patients continue to be prescribed subtherapeutic doses of pain medications resulting in undue suffering and diminished quality of life. Pain associated with malignancy and its treatment may exacerbate other symptoms associated with cancer, including nausea, fatigue, weakness, dyspnoea, constipation and impaired cognition. The choice of analgesic pharmacotherapy should be individualised and based on the intensity of pain reported by the patient, rather than its specific aetiology. When selecting pain management pharmacotherapy, the healthcare provider should consider the patient's pain level, activity level and any comorbid illness. Intolerable adverse effects, ineffective pain relief or a change in the patient's clinical status can dictate the need for a new pain management regimen. Healthcare providers must be able to readily quantify the relative analgesic potency when converting from one opioid to another or from one route of administration to another. Transdermal formulations of fentanyl and buprenorphine are effective pharmacotherapy that can be safely used for cancer patients with pain. However, clinicians need to be cognisant that the US/UK manufacturer's recommendations for equianalgesic dose administration of transdermal fentanyl may result in initial doses that produce subtherapeutic concentrations and unrelieved pain in some patients. A less conservative dose administration algorithm for transdermal fentanyl using a 2:1 (mg/day of oral morphine : microg/h of transdermal fentanyl) conversion ratio that considers both a review of the literature and clinical experience should help clinicians individualise cancer pain pharmacotherapy.