Antidepressants may reduce efficacy of opioid pain medication: Study

The retrospective cohort study, comprised reviews of the medication records of 152 patients, admitted as inpatients or observation status, at two US-based university hospital medical centres who received scheduled tramadol for at least 24 hours.
 
The results found those who were also taking the antidepressants fluoxetine, paroxetine or bupropion required ‘significantly more’ pain medication per 24 hours to control breakthrough pain throughout the day, when compared with patients not taking antidepressants.
 
‘As we looked at the secondary analysis, it ended up being four times as much over their entire hospital stay,’ lead study author Derek Frost said.
 
Mr Frost said the results demonstrated a clinically relevant decrease in the efficacy of tramadol when used for pain control in patients receiving a strong CYP2D6 inhibitor.
 
‘Tramadol relies on activation of the CYP2D6 enzyme to give that pain control,’ he said.
 
‘This enzyme can be inhibited by medications that are strong CYP2D6 inhibitors, such as fluoxetine, paroxetine and bupropion.’
 
According to the researchers, these drugs are common antidepressants, and the fact depression and anxiety often go hand in hand with chronic pain means the likelihood that a patient is taking one in combination with tramadol is ‘relatively high’.
 
‘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,’ Mr Frost said.
 
Alternative SSRIs in the same class of medication, such as sertraline, citalopram and escitalopram, do not inhibit the CYP2D6 enzyme. Researchers recommend other options for patients in the way of pain management, such as nonsteroidal anti-inflammatory drugs (NSAIDs).
 
‘Non-opioid medications are an option ... [but] if we need to use opioids, a scheduled morphine or a scheduled oxycodone would avoid this interaction,’ Mr Frost said.
 
The study also underlines the importance of healthcare providers being aware of the potential interactions for patients who have a combination of chronic pain and depression or anxiety – some of whom may be suspected of drug-seeking behaviour when, in fact, they may be under-medicated and seeking more effective pain relief.
 
This is the first study to document the effects of the interaction of tramadol with the antidepressants fluoxetine, paroxetine or bupropion in a real-world setting with patients on existing medication.
 
Researchers hope the results will encourage healthcare providers to review medication lists for the interaction between common antidepressants and tramadol, and adjust regimens accordingly to ensure adequate pain control, also helping to reduce risk of addiction if they exceed the prescribed dose of tramadol.
 
‘For patients who have the combination of chronic pain and depression or anxiety, keep in mind that this interaction does exist, and if you have a patient approaching you saying, “This medication isn't working for me”, is there an interaction at play?’ Mr Frost said.

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