When it comes to discussions about opioid drugs in the media, they almost always focus on the potential for abuse and addiction.  In the chronic pain community, the discussion often centers around how difficult it is to find a doctor who will prescribe the pain medications we need and the stigma placed on anyone taking opioids, regardless the reason.  What we rarely, if ever, hear is an educated discussion of the possible dangerous interactions that may occur when we take other medications in addition to the opioids. 

It is estimated that 70 percent of patients taking an opioid pain reliever also take at least one nonprescription drug or substance and a majority also take one or more prescription medications.  It is so important to be aware of possible interactions whenever any drug is mixed with one or more other drugs or supplements.

Complexities of Opioid Interactions

A drug interaction occurs when two or more substances (drugs, supplements, or even some foods) affect each other in such a way that the metabolism, elimination, effectiveness, and/or toxicity of one or more of the drugs is changed.  Simply put, a drug interaction causes one or more of the medications you're taking not to work as they should.  This can have dangerous, even deadly, results. 

One of the more complex problems when it comes to drug interactions in general and opioid-drug interactions in particular involves the enzymes our bodies use to metabolize the medications.  According to Dr. Stewart B. Leavitt, Executive Director of Pain Treatment Topics, “A special concern is with drugs metabolized and cleared via the cytochrome P450 (CYP450) enzyme system, primarily in the liver. While this is a complex subject, and there are dozens of different CYP450 genes in humans, relatively few of the gene-encoded enzymes play a role in drug metabolism; most prominently involved are the CYP1, CYP2, CYP3 families and the CYP3A4 and CYP2D6 isoforms.”

Sound like Greek?  I agree.  Basically what happens is that when two or more medications that are metabolized by the same enzyme(s) are taken, they complete with each other for use of the enzyme(s).  The drug that attracts more of the enzyme(s) is the winner.  If the opioid “wins” it may be metabolized more quickly than it should be and the pain relief won't last as long as it should.  If the opioid loses the race, it can be metabolized more slowly than it should be.  That not only means you'll get less pain relief than you should, but it could result in toxic accumulations of the opioid in your system, which could cause an accidental overdose. 

When it comes to opioid pain relievers, a few like morphine, hydromorphone, and oxymorphone are basically unaffected by CPY450 metabolism.  Most other opioids, including, codeine, hydrocodone, oxycodone, tramadol, fentanyl, and methadone, are metabolized via CYP3A4 and CYP2D6.  Methadone also uses CYP1B6.  If you are taking other medications that rely on the same enzymes for metabolism, you could be facing an opioid-drug interaction problem.