Narcotic conversion


  1. This is a rough guide only; adsorption rates vary between patients and adjustments will be required
  2. See below for duration of effect of common narcotics
  3. For patients on very high doses, or other narcotics, consult pain expert, pharmacist or Lexicomp in ‘EPIC Resources’

How to calculate:

  1. Add up total dose taken by patient in 24-hrs
  2. Convert from one drug to another
  3. Divide total 24-hr dose by appropriate number of intervals, may need to round based on how drug supplied, and if having more pain than usual
  4. Add breakthrough prn doses
  5. Reassess orders frequently and adjust based on effects


Example case: Person normally takes long-acting oral morphine 30 mg at home twice a day and rescue morphine 5 mg average 3 times per day  > need to convert to S/C  hyromorphone while NPO in hospital

Morphine = (30 x 2) + (5 x 3) = 75 mg per day oral morphine

Hydromorphone = 75/30 * 2 = 5 mg per day or 0.83 mg q4h S/C hydromorphone

Order hydromorphone 0.5 or 1 mg q4h S/C straight, depending on degree of pain, plus breakthrough prn such as hydromorphone 0.5 – 1mg S/C q4h prn


Duration of effect of common narcotics, based on drug and route


  1. Duration can be prolonged by age, frailty, renal or liver dysfunction
  2. IV push (other than patients on APS or CADD pump ) may require enhanced monitoring; consult hospital policies




  1. Compendium of pharmaceuticals and specialties. Opioids general monograph. Canadian Pharmacists Association. Ottawa, Canada. c 2013