Guaifenesin for Fibromyalgia


Guaifenesin is a medication used primarily to relieve chest congestion. It is a common ingredient in many over-the-counter cough and cold medications (such as Robitussin or Mucinex), which may also contain antihistamines, cough suppressants, and nasal decongestants. Although it cannot treat the underlying cause of congestion, it works by helping to control the symptoms. Guaifenesin is one of a number of medications in the drug class known as expectorants. It works by thinning mucus in the airways of the lungs, which makes it easier to cough up and clear air passages. Guaifenesin comes in a variety of forms, including tablets, capsules, and liquid. It can generally be taken every four hours as needed, whereas extended-release versions of products containing guaifenesin are typically dosed every 12 hours.

History of Guaifenesin in the Treatment of Fibromyalgia

For decades, Dr. R. Paul St. Amand, M.D. has claimed that guaifenesin is an effective treatment for fibromyalgia symptoms. Dr. St. Amand theorizes that a defect in the body’s ability to metabolize phosphate, which in turn leads to defective energy production by skeletal muscles, is a primary cause of fibromyalgia. His theory posits that guaifenesin is able to alleviate fibromyalgia symptoms by removing excess phosphate from the body. In a paper published on his website, Dr. St. Amand provides evidence for this theory based on his own historical clinical and laboratory experience, but provides no concrete scientific evidence to support the role of impaired phosphate metabolism in the onset of fibromyalgia, with the exception of one small review article published in 1989 (Bengtsson & Henriksson, 1989). This review article references a small study conducted by Bengtsson et al. in 1986, in which various muscle biopsies were performed on 21 fibromyalgia patients and eight healthy control subjects. The study found abnormal phosphate levels in fibromyalgia patients and provided support for the then-emerging theory that the pain associated with fibromyalgia was of a muscular origin (Bengtsson et al., 1986).

Some researchers have continued to investigate phosphate levels in the muscles of fibromyalgia patients. Although abnormal levels of certain phosphates and phosphate metabolites have been detected in some studies and therefore suggest a possible relationship to weakness and fatigue by way of decreased energy production (Sportt et al., 2000; Park et al., 1998), no studies have shown conclusive evidence that fibromyalgia symptoms are directly related to phosphate levels (Sportt et al., 2000). Furthermore, some studies have found no differences in the muscle levels of phosphates between fibromyalgia patients and healthy controls (Simms et al., 1994; Jacobsen et al., 1992; de Blecourt et al., 1991).

Nevertheless, Dr. Amand maintains that guaifenesin is an effective therapy for fibromyalgia, and has published a protocol for treatment on his website (please refer to the St. Amand & Marek reference at the end of this paper). In its most simple form, the treatment protocol requires that patients begin with a 300mg of long-acting guaifenesin twice daily for one week. This therapy is unconventional in that in order to establish that the therapy is “working,” patients’ symptoms must first worsen before they will improve. If symptoms do not deteriorate within one week of initiation of guaifenesin therapy, the dose is then increased to 600mg twice per day. The protocol states that only 20% of patients will required a higher dose than 1200mg total per day. In addition to the actual treatment with guaifenesin, the protocol dictates that patients refrain from consuming or using any products that contain salicylates (salts of salicylic acid) during the course of their treatment. Dr. St. Amand stresses that salicylates can interfere with the effects that guaifenesin has on fibromyalgia symptoms. A description of the list of “banned” salicylate-containing products mandated by the treatment protocol is beyond the scope of this paper, however the general categories of such products include various pain medications, specific herbal supplements, certain cosmetic products and toiletry items, and various oral hygiene products including some toothpastes and mouthwashes.

Research Related to Guaifenesin and Fibromyalgia

During the 1990s, Dr. St. Amand joined prominent fibromyalgia researcher Dr. Robert Bennett in an effort to study the effects of guaifenesin on fibromyalgia. The results of this study showed that guaifenesin had no effect on fibromyalgia. Although the study was never published, the findings were widely publicized and spurred considerable debate between the two researchers and others. Dr. St. Amand argued that patients in the study who did not experience any benefit from guaifenesin were unknowingly exposed to products containing salicylates. Dr. Bennett discounted this theory citing laboratory evidence that demonstrated no excess exposure to salicylates among the patients who participated in the study. He further argued that Dr. St. Amand’s historical success with treating patients with guaifenesin could be due in large part to what is known as the “placebo effect.” The placebo effect can best be described as a phenomenon by which a patient’s symptoms are relieved by an ineffective treatment due to the patient’s own perception of the treatment as effective. 

Beyond this study, there is only one other study that provides evidence documenting the use of guaifenesin to treat fibromyalgia. In this study, 434 female fibromyalgia patients and 198 healthy control subjects completed telephone surveys regarding their history of medication use. Among the fibromyalgia patients, 24.4% (106) reported having used guaifenesin as a treatment for their symptoms. In their discussion of the survey results, the researchers point out the fact that their study gained popularity with an Internet-based fibromyalgia discussion group that advocates the use of guaifenesin therapy, and as a result their findings related to guaifenesin were likely biased. Furthermore, the researchers cite the guaifenesin therapy protocol promoted by Dr. St. Amand, as well as anecdotal evidence from patients that attests to the efficacy of such therapy, however they make a point to mention that there are no published controlled studies related to guaifenesin therapy in the scientific literature (Shaver et al., 2009).



1.        AHFS Consumer medication Information. Guaifenesin.  Accessed April 18, 2012.

2.        St. Amand RP, Marek C. The use of uricosuric agents in fibromyalgia: theory, practice and a rebuttal to the Oregon Study of Guaifenesin Treatment. Clin Bull Myofascial Ther. 1997;2:5. Available atAccessed April 18, 2012.

3.        London M. The truths and myths of the use of guaifenesin for fibromyalgia or Guaifenesin: one medicine, several effects.   Last modified 12/05/2010; Accessed April 18, 2012.

4.        Bengtsson A, Henriksson KG. The muscle in fibromyalgia: a review of Swedish studies. J Rheumatol. 1989;16(Suppl. 19):144-149.

5.        Bengtsson A, Henriksson KG, Larsson J. Reduced high-energy phosphate levels in the painful muscles of patients with primary fibromyalgia. Arthritis Rheum. 1986;29(7):817-821.

6.        Sprott H, Rzanny R, Reichenbach JR, Kaiser WA, Hein G, Stein G. 31P magnetic resonance spectroscopy in fibromyalgic muscle. Rheumatology (Oxford). 2000;39(10):1121-1125.

7.        Park JH, Phothimat P, Oates CT, Hernanz-Schulman M, Olsen NJ. Use of P-31 magnetic resonance spectroscopy to detect metabolic abnormalities in muscles of patients with fibromyalgia. Arthritis Rheum. 1998;41(3):406-413.

8.        Simms RW, Roy SH, Hrovat M, Anderson JJ, Skrinar G, LePoole SR, Zerbini CA, de Luca C, Jolesz F. Lack of association between fibromyalgia syndrome and abnormalities in muscle energy metabolism. Arthritis Rheum. 1994;37(6):794-800.

9.        Jacobsen S, Jensen KE, Thomsen C, Danneskiold-Samsoe B, Henriksen O. 31P magnetic resonance spectroscopy of skeletal muscle in patients with fibromyalgia. J Rheumatol. 1992;19(10):1600-1603.

10.     de Blecourt AC, Wolf RF, van Rijswijk MH, Kamman RL, Knipping AA, Mooyaart EL. In vivo 31P magnetic resonance spectroscopy (MRS) of tender points in patients with primary fibromyalgia syndrome. Rheumatol Int. 1991;11(2):51-54.

Shaver JL, Wilbur J, Hyeongkyeong L, Robinson FP, Wang E. Self-reported medication and herb/supplement use by women with and without fibromyalgia. J Women’s Health. 2009;18(5):709-716.

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Shannon April 9, 2013 at 1:10 am

Thank you so much for providing such an easy to read, concise and thorough article about this confusing “protocol” that alleges a cure. I have had many a “discussion” on this topic over the years and I still have doubts on its validity. For the reasons you listed out!

Thanks so much for this article Terry!


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