Buprenorphine Conversion Considerations Interpreter

Buprenorphine does not fit an equianalgesic table: it is a high-affinity partial agonist with a ceiling on respiratory depression that can displace a full agonist and precipitate withdrawal. This page says what decides the answer instead of inventing a ratio.

Why there is no ratio, in five properties

Every buprenorphine equivalence this page could find, with its source

The five properties that stop a ratio from working

The opioid that does not fit the table

Every other page in this category prints a ratio and argues about which one. This one does not, because buprenorphine is not a point on a potency scale and the sources that would have to supply the number either refuse to or publish something that is not a ratio at all.

Begin with the pharmacology, which is unusual in three ways at once. Buprenorphine binds the mu receptor with very high affinity but activates it only partly — NHS Lanarkshire’s peri-operative guideline puts it as “a very high affinity for opioid receptors though with relatively low intrinsic agonist activity”. Affinity and efficacy are separate properties and an equianalgesic table has a column for neither. Because the affinity is high, buprenorphine displaces full agonists that are already bound: “it can precipitate acute withdrawal as it displaces more potent but lower affinity opioids from receptors”. And because the efficacy is partial, the respiratory dose-response curve flattens — its own Summary of Product Characteristics describes it as “acting as a full agonist with respect to analgesia” but “as a partial agonist with respect to its respiratory depressant properties”, with a ceiling reported above 2 micrograms per kilogram intravenously. Equivalence assumes two parallel curves; one of these flattens and the other does not.

Then look at what the documents actually publish. CDC publishes nothing, and says so: in the words of Maryland’s reproduction of its factor set, “There is not a calculation to identify equivalency therefore MME is not available for buprenorphine products”. The BuTrans Summary of Product Characteristics, read end to end, contains no conversion ratio from any other opioid — section 4.2 says the product “can be used as an alternative to treatment with other opioids” from the lowest available patch strength with short-acting supplementary analgesia during titration, and section 4.5 records only that the transfer studies enrolled patients on up to 90 mg of oral morphine equivalent a day. That is an initiation strategy and an evidence boundary, not a ratio. The United Kingdom palliative care charts do publish a transdermal figure of about 2.4 mg of oral morphine a day per microgram an hour, and the BNSSG chart prints a range of roughly 1.8 to 3.25 round it and warns that ratios vary between brands; the table on this page reproduces all of it with the source against each row.

Two further things follow and neither is arithmetic. The patch is capped at two patches and 40 micrograms an hour, so the scale simply stops. And naloxone “may be less effective in reversing the effects of buprenorphine than other µ-opioid agonists”, which matters to anyone reading the opioid toxidrome with a buprenorphine patient in front of them. Every published conversion factor on this page is a population approximation with wide interindividual variability. The factor that fits the average of a cohort can be out by twofold or more in one person, because opioid absorption, clearance, active-metabolite handling and receptor pharmacology all differ between individuals. The equianalgesic tables these factors descend from were largely derived from single-dose studies in opioid-naive or acute-pain patients, and they are applied in practice to chronic, repeated dosing in people who are already tolerant — a use the original studies were never designed to support. Published practice when changing from one opioid to another is to reduce the calculated equivalent, and the reduction is applied after the equivalence rather than instead of it. The reason is incomplete cross-tolerance: tolerance to one opioid does not transfer fully to another, so the arithmetic equivalent over-estimates what the patient already tolerates. The Faculty of Pain Medicine puts the cut at 25 to 50 per cent, and at least 50 per cent above about 500 mg of oral morphine equivalent a day or in the frail and elderly; the other five sources read for this page put the first cut between 25 and 50 per cent and none puts it at zero; and MSD’s table raises it to 75 to 90 per cent for methadone. The figure this page returns is an arithmetic equivalence and nothing else. It is not a dose, not a target and not a limit, and no part of this page says what any patient’s dose ought to be. Your own formulary, local conversion chart or specialist pain or palliative care service governs: where it differs from anything here, it wins. For the opioids that do fit a table, with their disagreements printed, see the oral morphine equivalent page and the rotation page.

Frequently asked questions

Related calculators

References

1. BuTrans transdermal patch (buprenorphine). Summary of Product Characteristics, electronic Medicines Compendium. Section 5.1: “acting as a full agonist with respect to analgesia” but “as a partial agonist with respect to its respiratory depressant properties”, with “a ceiling effect has been reported following intravenous doses of greater than 2 μg/kg” and respiratory depression “a rare occurrence at therapeutic doses of the transdermal preparation” up to 40 micrograms an hour. Section 4.2 permits “no more than two patches” at once, “up to a maximum total dose of 40 microgram/hour”, and publishes no conversion ratio: it says only that the product “can be used as an alternative to treatment with other opioids”. Section 4.5 records that the transfer studies enrolled “subjects receiving full mu agonist opioids (up to 90 mg oral morphine or oral morphine equivalents per day)”, and section 4.9 that naloxone “may be less effective in reversing the effects of buprenorphine than other µ-opioid agonists”.
2. University Hospital Wishaw Acute Pain Service, NHS Lanarkshire. High Dose Buprenorphine: a guideline for the peri-operative care of opioid dependent patients, NHS Scotland Right Decision Service. “Buprenorphine has a very high affinity for opioid receptors though with relatively low intrinsic agonist activity”; “it can precipitate acute withdrawal as it displaces more potent but lower affinity opioids from receptors”; and the functional antagonism “may prevent full mu agonists from providing adequate analgesia necessitating high doses”, so that “high doses of buprenorphine can prevent prescribed full agonist opioids at conventional doses from alleviating acute pain”.
3. Maryland Department of Health, Prescription Drug Monitoring Program. MME Fact Sheet. Reproduces the pre-2022 CDC factor set row for row, adds buccal, sublingual and lozenge fentanyl at 0.13 per microgram, lists no factor for tramadol, and states of buprenorphine that “There is not a calculation to identify equivalency therefore MME is not available for buprenorphine products”. Used here as the independent corroboration of CDC’s own CQL library, which renders truncated. At 50 MME a day it advises monitoring pain and function more frequently and discussing dose reduction, tapering or discontinuation if benefits do not outweigh harms.
4. NHS Bristol, North Somerset and South Gloucestershire ICB. Opioid conversion charts — adults, 2024, version 3.1. Prints the fentanyl and buprenorphine patch equivalences in four columns at once — BNF/Faculty of Pain Medicine, the Summary of Product Characteristics band for a stable patient, the band for rotation or a less stable patient, and a local figure — so the disagreement is visible on one page. Potencies: codeine 0.1, dihydrocodeine 0.1, tramadol 0.1, oral oxycodone 1.5, tapentadol 0.4, hydromorphone 5. States that the calculated equivalent dose is reduced in most cases when switching, and that its table is not for opioid-naive patients.
5. Severn Hospice. Opioid Conversion Table, version 07.19. Oral potencies of 0.1 for codeine and dihydrocodeine but 0.15 for tramadol, and oral oxycodone reached by dividing oral morphine by 2 — two figures that disagree with the Faculty of Pain Medicine’s 0.1 and 1.5 for the same drugs. Transdermal fentanyl “approx. 100 to 150 times more potent than oral morphine” with the table built at 100:1; buprenorphine 5 micrograms an hour matched to 12 mg of oral morphine a day. Puts the switching reduction at 25 to 30 per cent, and at 50 per cent when converting high doses, to avoid toxicity.
6. Faculty of Pain Medicine of the Royal College of Anaesthetists. Opioids Aware: dose equivalents and changing opioids. Oral potencies, reviewed March 2023 against the BNF: codeine 0.1, dihydrocodeine 0.1, hydromorphone 5, morphine 1, oxycodone 1.5, tapentadol 0.4, tramadol 0.1, methadone “varies” with specialist advice required. Transdermal fentanyl 12, 25, 50, 75 and 100 micrograms an hour against 30, 60, 120, 180 and 240 mg of oral morphine a day. Conversion factors are an approximate guide only “because data are incomplete and individual variation is significant”; in most switches the calculated equivalent is cut by 25 to 50 per cent, and by at least 50 per cent above about 500 mg of oral morphine equivalent a day or in the elderly or frail; and “Opioid rotation is not recommended if a patient has responded to one opioid”.

Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/