Opioid conversion ratios used in palliative care: is there an Australian consensus?

BACKGROUND: Opioid switching or rotation is reported to be a common practice in palliative care. Published tables of opioid conversion ratios have been found to vary in their recommendations, potentially leading to significant differences in clinical practice.

AIMS: To identify common practices in the calculation of opioid equianalgesia by specialist palliative medicine practitioners and trainees.

METHOD: An anonymous, cross-sectional, online survey completed by 85 Australian palliative care specialists or advanced trainees. Questions focused on conversion ratios used in switching between oral and parenteral opioid doses; conversion ratios used when switching from other opioids to oral morphine; and practice of commencing methadone.

RESULTS: The majority of respondents calculated equianalgesic doses for morphine, oxycodone and hydromorphone using the same conversion ratios. Methadone was used almost equally as either the sole opioid or as a 'co-opioid'. The majority surveyed converted slow-release hydromorphone differently to the manufacturer's recommendations.

CONCLUSION: Further discussion among Australian palliative care specialist organisations is recommended in order to produce uniform conversion guidelines to improve consistency and safety in the prescribing of opioids.