Converting Between Opioids
When switching between opioids, the goal is to achieve an equianalgesic effect. Equianalgesic conversion tables are based on opioid-naïve patients with acute pain. Table 4 provides an example of equivalent dosing for the commonly chosen drugs. A number of factors must be taken into account when making the switch. In general, to switch between opioids, a rough estimation of the 24-hour dose should be calculated, converted to the new opioid, and then divided by the desired dosing schedule.
A patient who has been taking an opioid for an extended period of time may develop a degree of tolerance to it; however, when converting to another opioid, only a part of this tolerance may carry over to the new drug. Therefore, after calculating the required dose of the new drug to achieve an equianalgesic effect, the dose may need to be lowered by up to 50%. Because this phenomenon is difficult to predict on an individual basis, any opioid conversion requires close monitoring.
Similarly, patients who are being converted from a long-acting opioid formulation should first be stabilized on the immediate-release form of the new drug. Once a stable standing dose is re-established, a slow-release dose can be introduced.
Geriatrics and Aging. 2009;12(1):48-52. © 2009 1453987 Ontario, Ltd.
Cite this: Prescribing Opioids to Older Adults: A Guide to Choosing and Switching Among Them - Medscape - Jan 01, 2009.