Tables showing equianalgesic doses of narcotic agents can be used to determine the dose of a different narcotic with approximately the same amount of analgesia to the current medication.
NOTE: Problems in comparing equianalgesic narcotic doses:
(1) duration of patient exposure: acute/intermittent vs chronic/continuous usage
(2) route: oral vs parenteral vs transdermal vs rectal
(3) severity of underlying pain and whether it was established before starting analgesia
(4) duration of drug effect: normal kinetics vs extended dose release
(5) age, body weight and comorbid conditions of the patient
(6) interindividual variability in relative potency for each narcotic agent
(7) the protocol (single dose, infusion, multiple doses) by which the drug comparison was conducted
NOTE: All of the doses were adjusted from the original source data to be equivalent to 10 mg oral morphine, chronic/continuous exposure, for an adult.
30 – 40 mg
3 – 5 mg
use in program
• The conversion from oral to parenteral morphine is 6:1 when with acute and intermittent use, but 2:1 or 3:1 with chronic and continuous use.
• The equianalgesic dose of oral morphine for acute, intermittent doses is 60 mg vs 30 mg for chronic, continuous doses. This means that you need to reduce the drug dose if you go from infrequent, intermittent dosing to continuous dosing.
3 – 4 mg
Codeine (with ASA or Tylenol)
20 – 40 mg
16 - 33 mg
• Meperedine has a number of problems as an analgesic agent and does not appear to be recommended for control of terminal cancer pain. A toxic metabolite may accumulate in renal failure.
8 - 10 mg
varies with morphine dose
In the implementation:
(1) Each opioid is divided by its equianalgesic dose to give a number of "analgesic units" that can be summed to give a total for 24 hours.
(2) The number of units can then be multiplied by the equianalgesic dose for a single agent to give the amount of that agent needed to provide "equivalent" analgesia.
NOTE: The equianalgesic dose may not be the dose of the new drug that you should choose to administer to the patient. If going from intermittent to continuous dosing it may be necessary to use a lower dose, while going from continuous to intermittent may require a higher dose. Usually a lower dose is selected to avoid adverse effects and to rely on rescue doses to control the pain.
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Specialty: Pharmacology, clinical