Taking Antidepressants for Pain Relief - Facts And Information
My doctor says that I have “myofascial back pain.” He has also ordered me an antidepressant to take to decrease the pain. I did not think that I was depressed. So now I am a bit confused – I even wondered if the pharmacy gave me the wrong medication. Can you explain why an antidepressant is used for pain?
Sometimes doctors fight pain with antidepressants and prescribing antidepressants for pain is probably one of the most confusing areas for patients to understand. Patients are often confused by the use of antidepressants for pain because the names of these medications do not reflect all of the possible things that they do. For instance, antidepressants reduce depression and we think they do so by a mechanism called “re-uptake inhibition” of brain chemicals called serotonin and norepinephrine. Almost all mainstream antidepressants share one or both of these mechanisms.
However, only one group of antidepressants also has additional local anesthetic effects (numbing effects) aside from its antidepressant properties. The mechanism by which these antidepressant drugs act like local anesthetics is called “sodium channel blockade.” This is not something shared by antidepressants such as Prozac®, Paxil™ and Zoloft® or the other antidepressants in the “selective serotonin re-uptake inhibitors” group (or also simply called the SSRI group). It is only the tricyclic antidepressants that have this local anesthetic-type property and therefore, it is only this group of antidepressants that seems to have pain-relieving properties that are independent of their effects on reducing depression. The typical type of pain that is treated by local anesthetics is nerve injury-type pain and tricyclic antidepressants are also effective in combating nerve injury pain. Thus, tricyclic antidepressants may help with the pain from nerve injury even for non-depressed patients. Typical tricyclic antidepressants include medications such as amitriptiline (Elavil®), or cousins of these drugs called imipramine (Tofranil®), nortriptiline and desipramine. Other antidepressants (other than the tricyclic group) may also help with pain from nerve injury but for reasons that are not as well studied. These include venlefaxine (Effexor) and the newly approved duloxetine (Cymbalta.)
The tricky part comes when patients are depressed and have pain. Depression has an amplifying effect on pain. By decreasing depression, we can de-amplify the sensation of pain, and therefore decrease pain. In my opinion, decreasing depression when it is also present with pain is a very significant intervention for decreasing pain itself and improving the patient’s ability to cope with any pain sensations that they have.
The problem with the tricyclic antidepressants, or the antidepressants that are most well studied to help with pain, is that they often have unwanted side effects. These side effects include sedation, lowered blood pressure, constipation, diminished sexual function and many others. The newer antidepressants, such as the SSRIs, seem to be just as effective for treating depression, but don’t have as many of these side effects. In treating depression, doctors often need to get to higher doses of antidepressant medications. Higher doses of the tricyclic antidepressants often have unwanted side effects. So in patients who are depressed, I tend to choose to use the newer & better-tolerated antidepressants (such as SSRIs antidepressants) rather than trying to treat both the pain and treat the depression as well with one single drug. The newest entry into the field of antidepressants is duloxetine (Cymbalta), a drug that also has FDA approval for use in nerve injury pain. This is the first drug that the FDA had indicated may be useful as a single agent against depression and pain. Nonetheless, many other drugs may be equally effective at treating both but have not gone through the rigorous and costly process of seeking approval from the FDA.
When patients suffer with chronic pain, it is also very important for patients to discuss any symptoms of depression with their doctor. The question almost always arises: which problem came first, the pain or the depression? If doctors treat the pain, maybe the depression will go away. If doctors treat the depression, maybe the pain will go away. These questions are usually circular and do not usually have a crystal clear answer to solve the problem. In my clinic, we go right after all of the symptoms that are present at the time.