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Calculator · Convert to oral morphine equivalent and back
Opioid conversion
Every ratio here is the one already written into this app's opioid pathway, so the calculator and the pathway cannot drift apart. The answer is deliberately given as a range after a dose reduction — converting at full equivalence is the error that causes the…
Before you use it
NEVER convert methadone or buprenorphine by ratio — both have pharmacokinetics that make equianalgesic tables meaningless, and both need specialist advice. Fentanyl and buprenorphine PATCHES are not on this screen for the same reason: the patch is a 72-hour depot, the ratios are wide, and the pathway quotes 25 mcg/hr as roughly 60–90 mg of oral morphine a day, which is a range too broad to prescribe from without help. Every conversion needs a second check by another prescriber, breakthrough recalculated as one sixth of the new 24-hour dose, and a review within 24 hours. In renal impairment the drug should probably change, not just the number.
Source: Matches pathway 97 (Opioid Toxicity & Conversion); Faculty of Pain Medicine
Checked, and shown
Every threshold on this page was checked against its primary source by a practising doctor. Here is what that involved, and what it found.