By Pat Anson, PNN Editor

Common antidepressants interact with the opioid medication tramadol to make it less effective for pain relief, according to a small new study from University Hospitals (UH) in Cleveland. The findings suggest that some patients who exceed their prescribed dose of tramadol may be under-medicated and are seeking more effective pain relief.

Prescriptions for tramadol – which is sold under the brand names Ultram and ConZip – have increased in recent years because it is widely perceived as a “safer” opioid with less rick of addiction. Many patients, however, say tramadol is not as effective as hydrocodone, oxycodone and other opioids.  

UH researchers reviewed the prescription records of 152 patients who received tramadol for at least 24 hours.

Those patients who were also taking the antidepressants Prozac (fluoxetine), Paxil (paroxetine) or Wellbutrin (bupropion) required three times more tramadol per day to control their breakthrough pain, compared to patients not taking the antidepressants.

Previous studies on healthy volunteers have shown effects on blood levels when combining tramadol with those particular antidepressants. However, this was the first study to document the effects of this interaction in a real-world setting with pain patients.

"We knew that there was a theoretical problem, but we didn't know what it meant as far as what's happening to pain control for patients," said Derek Frost, PharmD, a UH pharmacist and lead author of the study, which was published in the journal Pharmacotherapy.

Frost says millions of Americans may be suffering the ill effects of this drug-to-drug interaction.

"Tramadol relies on activation of the CYP2D6 enzyme to give you that pain control," Frost said. "This enzyme can be inhibited by medications that are strong CYP2D6 inhibitors, such as fluoxetine, paroxetine and bupropion.

“Many chronic pain patients are taking antidepressants, mainly selective serotonin reuptake inhibitors (SSRIs), which many of these CYP2D6 inhibitors fit into. There are a lot of patients who experience both, unfortunately. The likelihood that somebody on one of these offending agents and tramadol is relatively high."

Frost says the problem has a relatively easy fix.

"We have a lot of other antidepressants available that are in the same class of medication that don't inhibit this particular enzyme, such as Zoloft (sertraline), (Celexa) citalopram and Lexapro (escitalopram)," he said. "You also have other options for pain control - non-opioid medications such as NSAIDs. If we need to use opioids, a scheduled morphine or a scheduled oxycodone would avoid this interaction."

Tramadol is a synthetic opioid that was rescheduled by the Drug Enforcement Administration in 2014 as a Schedule IV controlled substance, a category that means it has a low potential for abuse. That same year, hydrocodone was rescheduled as a Schedule II drug, meaning it has a high potential for abuse. Many patients who were taking hydrocodone were switched to tramadol as a result of the rescheduling.