Jeffrey Fudin, PharmD, said that evidence published in an article in Pain Medicine in 2012 “suggests that the use of dose conversion ratios published in equianalgesic tables may lead to fatal or near-fatal opioid overdoses.”
He said opioid rotation is common in clinical practice for several reasons. For example, opioids may be switched when pain is not under control and doses cannot be escalated, when adverse events or toxicity occurs, when patients develop rapid tolerance, or when opioid-induced hyperalgesia is suspected.
Specifically in chronic pain patients, opioid rotation is reported to offer better pain control, and due to patient differences, opioid rotation may be required to find the best fit.
Opioid conversion doses can be found in package inserts, primary literature, textbooks, websites, and online calculators.
Fudin and his team found eight online opioid conversion calculators
When the remaining calculators were compared to each other, a +242% variation in recommended methadone does was seen in the results. A positive variation carries a risk of overdose and death, while a negative variation carries a risk of underdose and withdrawal, Fudin explained. He also reported a +100% variation for fentanyl.
Fudin has also studied the top mathematical models for calculating opioid conversion doses, and he has developed his own formula using the most conservative approach
Fudin’s formula has now been incorporated into the online calculator that is available on the Practical Pain Management website.
Slow titration, clinical judgment, and individualization of treatment are necessary to safely and effectively switch a patient from one or more opioids to another,” Fudin concluded.
Although methadone accounts for only 2 percent of opioid prescriptions, it caused nearly one in three prescription opioid overdose deaths in 2012
In my experience, methadone feels categorically different than the more common opiates used for pain management, like oxycodone and hydrocodone. More addictive than all other opioids (even heroin), dependence sets in quickly.
Methadone seems to be not only more potent, but also to develop a stronger grip on a person (I don’t know how else to describe it) so that a slight delay or decrease in dosage immediately triggers withdrawals. This opiate scared me.