Methadone and fluconazole: respiratory depression by drug interaction

A 60-year-old man with advanced gastric cancer achieved good pain control on a stable dose of methadone for 10 days. However, he developed respiratory depression 2 days after intravenous fluconazole was administrated for refractory oral candidiasis. Intravenous naloxone effectively reversed the respiratory depression. This case illustrates a significant interaction between methadone and fluconazole, and highlights the need for awareness of potential interactions between drugs used in palliative care.