Cautious use and optimal dose of morphine for relieving malignant pain in a complex patient with multiple comorbidities.

Oral morphine remains the drug of choice for the management of severe pain due to cancer as per WHO ladder of analgesia. Providing adequate pain relief in palliative care settings for pain due to cancer is challenging. Options become limited in cases of associated systemic comorbidities such as renal dysfunction, hypoproteinaemia, anaemia. Patients with renal dysfunction and other comorbidities may develop drug overdose due to abnormal pharmacokinetics. Renal dysfunction affects the pharmacokinetics of morphine by altering its absorption, metabolism and clearance. Plasma albumin also influences drug availability, its plasma distribution and thus available free morphine for its clinical effect. Morphine should be used cautiously for the treatment of pain in patients with renal failure, hypoproteinaemia, hyperbilirubinaemia and anaemia. In such patients, alternate opiates like fentanyl, hydromorphone, or oxycodone may be used as these drugs are not significantly excreted by the kidneys. 2016 BMJ Publishing Group Ltd.