Consumer Alerts



Guaifenesin is a cough syrup expectorant, but there is a popular theory that it works to help with the pain and other symptoms of fibromyalgia. Now that guaifenesin is also available over-the-counter, it is all the more important that patients be armed with the research on this study. Yes, there was a research study conducted to look at the potential effect of guaifenesin in people with fibromyalgia. Due to the negative results, the study was never published in a peer-review medical journal (so it is not on PubMed), but Fibromyalgia Network interviewed the lead author of the study and wrote the article Guaifenesin … Is One Placebo Better Than Another? below.

After the study showed that guaifenesin performed no better than a placebo, and the blood/urine tests revealed that it could not possibly work as suggested by Paul St. Amand, M.D., the guaifenesin controversy is still alive. Despite St. Amand’s role as advisor for the study design (he selected the doses, etc.), he has since published a book on how guaifenesin can “cure” people with fibromyalgia. There is also a new cosmetic line that does not contain salicylates (vigorously marketed to people trying the quaifenesin protocol as outlined in St. Amand’s book). It is just one example of how marketing “cures” for fibromyalgia without a shred of evidence can add to the wealth of some. The promise of a “cure” sells books, but it also tarnishes the reputation of people with this chronic illness and damages their relationships. With so many bogus cures in the media, patients have a difficult time explaining to family and friends why it is that they are not going to pay for this or that to “cure” themselves!

Guaifenesin – Is One Placebo Better Than Another?

At the 1996 Orlando American College of Rheumatology meeting, Robert Bennett, M.D., presented the results of his one-year placebo-controlled trial of guaifenesin, a common ingredient in cough syrups. The Oregon Health and Science University professor from Portland posed the following question at the opening of his speech: “Why on earth would someone choose to study an expectorant for the treatment of fibromyalgia?” Bennett says: “The answer lies in the realm of popular demand.”

For years, guaifenesin has been promoted as a cure for fibromyalgia. The theory behind the use of this drug is to rid the muscles, tendons, joints, brain, intestines and other tissues of harmful calcium phosphate deposits. These deposits, similar to tartar buildup on teeth, were speculated to be caused by an inherited defect in kidney function that would ordinarily flush the phosphate molecules into the urine where they belonged. Instead, these deposits were believed to cause serious impediment of blood flow to these tissues, resulting in an impairment of vital cellular functions throughout the body. Naturally, if this were truly the case, it could explain the widespread pain and bodywide dysfunction that fibromyalgia patients have.

Drugs that can draw the phosphate deposits out of the body should be able to correct this inherited defect. It has been claimed that guaifenesin works on the kidneys to mildly increase the excretion of uric acid and possibly to increase phosphate excretion. Thus, it was hypothesized that drugs which increased uric acid secretion (uricosuric agents) could also increase phosphate secretion and vice versa. Given the above hypothesis and the reported actions of guaifenesin, everything seems to fit into place.

So if you are a longtime reader of the Fibromyalgia Network Journal, you must be wondering why we haven’t ever mentioned guaifenesin. Numerous and extensive muscle studies, including those by seasoned researcher Muhammad Yunus, M.D., of University of Illinois College of Medicine, have never revealed or even hinted that calcium phosphate deposits were a problem in fibromyalgia. Elaborate muscle metabolic studies such as the 1993 one by Boston University researcher Robert Simms, M.D., turned up nothing, not even with the use of modern NMR spectroscopy. Intuitively, if large crystalline deposits were present throughout the muscles in patients with fibromyalgia, you would think that they would show up in at least one study involving the muscles, wouldn’t you?

But as Dr. Bennett explained, the study of guaifenesin for the treatment of fibromyalgia had to do with the patient demand for this drug and the frequent claims on the Internet and elsewhere that it was a cure for fibromyalgia. The proponents of this “cure” often claimed guaifenesin wasn’t for wimps! Yes, as this drug was drawing the calcium phosphate deposits out of your tissues and into your bloodstream, you would have to go through symptom flare-ups. In the long run, after cycling in and out of severe pain, guaifenesin would rid your body of the damaging effects of these deposits. As long as you stayed on a maintenance dose of this drug, you would live out the rest of your life pain free. What an enticement, especially for patients who are already up to their eyeballs in pain!

The likelihood that guaifenesin was a cure for fibromyalgia was slim, but for the benefit of patients who were dumping conventional therapies to try it, guaifenesin needed to be tested. Dr. Bennett agreed to take on the arduous task of a one-year double-blind, placebo-controlled study to get to the truth about guaifenesin. Twenty female fibromyalgia patients were placed on 600 mgs of guaifenesin twice a day and another 20 patients took a placebo (sugar pill) twice daily. None of the patients knew what they were taking, but all were given the same instructions to not take salicylates (like aspirin) because they interfere with the functioning of guaifenesin. In addition, the evaluation nurses did not know what the patients were taking either (i.e., it was a “double-blinded study”). The study lasted for one year.

Bennett evaluated all study participants every three months for symptoms, tender points and serum/urinary levels of uric acid and phosphates. None of these variables significantly changed over the year and the response to guaifenesin was the same as that for the placebo. Now, what about the claims on the Internet and elsewhere that this study was fatally flawed because patients might have used cosmetics and other topical products that contain salicylates? Dr. Bennett provided six scientifically based reasons to toss out this claim:

  1. Both the serum and urinary levels of uric acid and phosphate were all in the normal range and no change was noted over time.
  2. If some patients were taking small amounts of salicylates by whatever method, there should have been a significantly reduced urinary excretion and elevated serum level of uric acid, but this was not observed.
  3. Dermatology consultants to Dr. Bennett have explained that patients would have to plaster their face with makeup several times a day to absorb enough salicylates to affect their urinary excretion of uric acid.
  4. Only in the last year have the proponents of guaifenesin therapy learned that cosmetics sometimes contain salicylates, yet they have been stating for years that this drug is a cure for fibromyalgia (without ever controlling for cosmetic use).
  5. The claimed “cycling of symptoms” was not observed in this study.
  6. Lastly, guaifenesin was not found to increase uric acid or phosphate excretions. Thus the postulated action of guaifenesin—the reason cited for its effectiveness—could not be demonstrated.

“I think my major comment is that the system works,” exclaims Bennett. “We have shown the placebo is just as effective as the placebo!”

For more information on Dr. Bennett’s guaifenesin trial, check out

NOTE: There is a small subgroup of fibromyalgia patients who claim that guaifenesin has significantly improved their symptoms. Perhaps it improves the airways for breathing during sleep? Whatever the mechanism (if it does help), it is not working by removing calcium phosphate crystals from the muscles.

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