Painkiller may raise seizure risk in seniors on antidepressants

By Stephen Beech

Tramadol can trigger seizures in older people when taken with certain antidepressants, new research suggests.

The prescription-only painkiller is linked to an increased risk of seizures in pensioners when combined with some pills for treating depression, according to the findings.

American researchers studied people living in nursing homes taking tramadol and some antidepressants that inhibit the CYP2D6 enzyme, called CYP2D6 inhibitors.

They found those antidepressants - such as fluoxetine, paroxetine and bupropion - block the CYP2D6 enzyme needed to metabolize tramadol.

People taking tramadol and CYP2D6 inhibitors had up to a 9% higher seizure risk than people taking tramadol and antidepressants that don't inhibit the enzyme, according to the study published in the journal Neurology.

While the study found a link between using the medications together and an increased risk of seizures, the research team emphasized that it does not prove one causes the other.

Tramadol is an opioid used to treat moderate to severe pain in adults.

Some antidepressants that inhibit the CYP2D6 enzyme, called CYP2D6 inhibitors, can interfere with how the body metabolizes tramadol.

When the CYP2D6 enzyme is blocked, the research team explained that tramadol is not metabolized properly and may build up in the body, potentially increasing the risk of side effects such as seizures.

Study author Dr. Yu-Jung Wei said: “We found a modest but measurable increase in the risk of seizures when tramadol was taken with antidepressants that inhibit the CYP2D6 enzyme.

“This risk was consistent whether the antidepressant or tramadol was started first.”

Researchers analyzed 10 years of medical data to identify 70,156 nursing home residents age 65 and older who had been prescribed both tramadol and an antidepressant.

They divided the participants into two groups based on which drugs they took first.

Of the participants, 11,162 people took tramadol first and then an antidepressant with it, while 58,994 took an antidepressant first and then added tramadol.

Seizure rates for people who took tramadol first were 16 seizures per 100 person-years, and for people who took antidepressants first, the rate was 20 seizures per 100 person-years.

The findings mean that for every 100 people who used both tramadol and an antidepressant followed for one year, about 16 to 20 suffered a seizure.

In both groups, researchers then compared seizure rates between those who took tramadol with CYP2D6-inhibiting antidepressants and those who took tramadol with antidepressants that do not inhibit the enzyme.

In those who took tramadol first and added an antidepressant, the rate was 18 seizures per 100 person-years for those taking CYP2D6-inhibiting antidepressants, compared to 16 seizures per 100 person-years in people taking other antidepressants.

In those who took antidepressants first and added tramadol, the rate was 22 seizures per 100 person-years for those taking CYP2D6-inhibiting antidepressants, compared to 20 seizures per 100 person-years in people taking other antidepressants.

To help ensure the differences were not due to other health issues, the researchers adjusted for factors such as pain levels, depression symptoms, physical function and cognitive ability.

After adjustments, for people who took tramadol first, the seizure risk was 9% higher when taking it with a CYP2D6-inhibiting antidepressant compared to with an antidepressant that did not inhibit the enzyme.

Among those who took an antidepressant first and added tramadol, the risk was about 6% higher for people who took a CYP2D6-inhibiting antidepressant compared to people who took an antidepressant that didn't inhibit the enzyme.

To test whether this interaction was specific to tramadol, the researchers repeated the analysis using hydrocodone, another opioid pain reliever that is unlikely to cause seizure risk when used with antidepressants.

No increased seizure risk was observed with hydrocodone and CYP2D6-inhibiting antidepressants.

Dr. Wei, of the Ohio State University in Columbus, Ohio said: “These findings underscore the need for careful prescribing practices, especially for older adults with complex health conditions."

She added: “Doctors should be aware of potential seizure risks when prescribing tramadol with antidepressants, particularly CYP2D6 inhibitors.

"Given how commonly both are prescribed to older adults, these interactions may be more important than previously thought.”