Medical calculators
Opioid Conversion
Equianalgesic Dosing
For education. Check every result.
Anatium is a study resource, not medical advice. Nothing here is a diagnosis, a prescription or a substitute for a clinician who has seen the patient. Check every number against a current local protocol before it touches anyone, and never act on a result you cannot reproduce yourself.
How it is calculated
Oral factors from the Faculty of Pain Medicine (Opioids Aware), parenteral from the UK Scottish Palliative Care Guidelines; the US CDC table differs for codeine (0.15) and tramadol (0.2). Conversion factors are approximate and vary between published tables. Reduce by at least 50% at 500 mg a day of oral morphine equivalent or more, or in the frail. Always reduce the calculated dose by 25-50% because cross-tolerance between opioids is incomplete - a mathematically equivalent dose is frequently an overdose. Fentanyl patches, methadone and buprenorphine are not included here: their conversions are non-linear - the methadone ratio changes with the dose being converted - and they should follow the product literature or specialist advice rather than any single factor.
About
Converts one opioid to an equianalgesic dose of another. Cross-tolerance is incomplete, so a mathematically equal dose is often an overdose; a reduction is applied automatically.
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