Converting one opioid to another
Step 1: Identify indications for switching opioids (adverse effects, poor analgesic efficacy, drug interactions, changes in clinical status, financial/social considerations); and determine total daily dose of opioid.
Step 2: Calculate equianalgesic dose of new opioid. Note: Due to variations of equianalgesic doses from different sources, this calculator uses Mean equianalgesic dose plus and minus one standard deviation if possible. Also, not all opioid convertions are bidirectional. You can convert other opioids to fentanyl, buprenorphine, or methadone; but not vice versa.
Use the calculator: 1. Select the old opioid from the From dropdown list; 2. Enter daily dose of the opioid in mg; 3. Select the new opioid from the To dropdown list. 4. Click the Calculate button. This may be optional because the calculator may automatically calculate.
Step 3: Reduce dose by 25-50% if incomplete cross tolerance exists or is suspected. Patient characteristics should be used to determine degree of reduction (i.e. elderly or frail patients should have dose reduction closer to 50%); If switching to methadone, doses should be reduced by 75%-90% and starting doses should not exceed 30 mg/day.
Step 4: Assess Patient carefully after transition and determine if dose should be increased/decreased by 15-30% based on pain severity, withdrawal, and/or side effects.