I was interested in the mechanism behind how capsaicin can provide some pain relief. I found a variety of articles and studies that have been conducted to test the effects of capsaicin on inflammatory conditions.
In an article titled, "Vascular and Sensory Responses of Human Skin to Mild Injury After Topical Treatment with Capsaicin", a general mechanism of action is discussed. The authors state that substance P causes vasodilation (also known as flare). As you may remember, I mentioned substance P in conjunction with calcitonin gene related peptide in my discussion of the anti-inflammatory actions of acupuncture. The authors also state that substance P is released from "central terminals of nociceptive afferent fibers." It is proposed that vasodilation after injury is partially caused by the release of substance P from these fibers.
The authors propose that treatment with capsaicin helps to decreases the levels of substance P that are released in the skin. Treatment with capsaicin is also thought to decrease the activity of some inflammatory agents.
Topical capsaicin may "deplete the skin nerve terminals of substance P." Substance P may also be "the agent that causes axon reflex flare."
However, I am still somewhat skeptical about the actions of capsaicin. The authors seem to feel similarly. They state that capsaicin has been shown to decrease the amount of dilator peptide (other than substance P) in the spinal cord. Over an extended period of time, capsaicin can actually "reduce the excitability of cutaneous nociceptors." This could lead to hypoalgesia and decreased flare, however that authors call this a toxic action.
It seems that capsaicin could have some concerning negative effects when used over a long period of time. Perhaps capsaicin is best used on a short time scale, for minor strains and sore muscles. After reading this article, I am curious as to how acupuncture can mimic the effects of capsaicin. It makes me wonder if there is any potential harm in having acupuncture over an extended period of time. Although, I have not heard of any data stating this.
Carpenter, Sandra E., and Bruce Lynn. "Vascular and Sensory Response of Human Skin to Mild Injury After Topical Treatment With Capsaicin." British Journal of Pharmacology 73.3 (2012): 755-58.
Interesting question at the end Diana...what I found to help answer about the risk involved with acupuncture is this: acupuncture is usually very safe and anything outside of that is because of mistakes by the acupuncturist. Some of the risks include: Fainting, bruising, muscle spasms, bleeding, nerve damage, punctured lung, and accidental injury to organs...
ReplyDeleteThat list is kind of crazy, huh??? But apparently these things do happen, though they are extremely rare. So be careful when choosing your acupuncturist!!!
https://www.acufinder.com/Acupuncture+Information/Detail/Are+there+risks+or+side+effects+to+acupuncture+
That....doesn't sound fun. Though it makes sense if you go to anyone who isn't trained or well trained in the act they are performing their are risks...like stabbing you in the lung with a sharp needle.
ReplyDeleteDiana does bring up an interesting point of possible long term side effects of acupuncture on the nervous system. Though I am sure reasonable portion of the negative side effects would be a result of the quality of the acupuncturist.
Thanks for looking up the side affects of acupuncture Maile.
ReplyDeleteI agree with both of you that acupuncture is most likely very safe. I thought it was an interesting question to pose after learning the negatives of capsaicin treatment, and then reading that acupuncture is similar to capsaicin treatment.
One thing that intrigued me about this post was the question if capsaicin should only be used for short term use. So I decided to see if I could find some more information on this! With my own knowledge though I know that Capasicin is actually something that is sold by nutrion websites as a form of fat burner. Many people who are trying to gain an edge in their weight loss plans or looking for a good fat burning stack will combine capsaicin based capsules with a regimen that typically includes things such as caffeine based stimulants, conjugated linoleic acid, l-carnitine, etc. Typcailly it is recommended that when taking these capsules you cycle on and off because otherwise it begins to lose its effectiveness. I think the same would happen in medicines that use this as a main ingredient.
ReplyDeleteOne medication I found that uses capsaicin as an ingredient is a medication called Zostrix. It is used to treat minor aches and pains of muscles/joints, and/or nerve pain. Its main ingredient is indeed capsaicin and works by decreasing a certain natural substance in your body (substance P) that helps pass pain signals to the brain (health central). There was an add for this drug in pharmacy times and it is marketed as a neuropathy cream to relieve diabetic foot pain and tingling. It is supposed to be rubbed on the foot until it gets absorbed between 2-4 times daily.
So to me this treatment sounds like it would be something that you couldn't consistently use, and you would have to wean yourself off of it.
http://www.healthcentral.com/chronic-pain/r/medications/zostrix-top-11201/uses?ic=506019
http://ezproxy.library.arizona.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true&db=a9h&AN=47567729&site=ehost-live
It's interesting you bring up the point of chronic use of capsaicin being bad and wondering if repeated acupuncture treatments could be bad because from the studies we went over in class it seemed that acupuncture had more beneficial effects with frequent treatments over a long timespan because the beneficial effects of acupuncture are short lived. I would think the negative effects of capsaicin would be repeated irritation to the skin which may end up causing chronic localized inflammation of the skin. I know that chronic inflammation can increase the risk of cancer so perhaps that is a risk of using it too often. After a quick google search it looks like I'm right "We have found that chronic, long-term topical application of capsaicin increased skin carcinogenesis in mice treated with a tumor promoter. These results might imply that caution should be exercised when using capsaicin-containing topical applications in the presence of a tumor promoter, such as, for example, sunlight"
ReplyDeletehttp://cancerres.aacrjournals.org/content/71/8/2809.full