Published on: July 13, 2017

In response to Pallium India’s newsletter of July 2017, Prof. June L. Dahl, Professor Emerita of Neuroscience, University of Wisconsin School of Medicine & Public Health, Madison, Wisconsin, writes to us:

I know it is common to refer to short-acting opioids as immediate release opioids. I believe drug companies coined the term ‘immediate release’ to distinguish the older (short-acting) drugs from the opioids that are specially formulated to provide a long duration of effect. The opioid is slowly released from those oral formulations. But short-acting opioids are not immediately released – it takes 45 minutes to an hour to achieve analgesic blood levels after ingestion of morphine sulfate, hydrocodone, hydromorphone or oxycodone tablets. That is not indicative of immediate release of these opioids. There are oral transmucosal delivery formulations of fentanyl that do provide more immediate release of fentanyl and a shorter duration of action than is characteristic of morphine, hydromorphone, hydrocodone or oxycodone tablets.

Knowledge of the pharmacokinetics of opioids is essential to the wise use of these drugs. I am wondering what clinicians expect from so-called immediate release formulations of opioid analgesics? Surely they can’t expect quick onset of action. Why can’t one use the accurate term to describe the short-acting drugs?

Thank you, Prof June Dahl, for pointing out to us that the use of the term ‘immediate release’ can be misleading.