Presented at the Annual Meeting of the American College of Rheumatology and Association of Rheumatology Health Professionals

October 18-22, 1996 - Orlando, Florida

Robert Bennett, Patricia deGarmo and Sharon Clark- Oregon Health Sciences University, Portland, OR 97201.

Guaifenesin (GF) - an expectorant - is widely touted by word of mouth and on the Internet as a cure for fibromyalgia (FM). The originator of this therapy postulates that FM is due to an inherited defect in the tubular reabsorption of phosphate with the resulting cellular accumulation of phosphate leading to malfunction of ATP dependent sarcomeric calcium pumps - causing muscle contractures. GF is claimed to reverse this defect due to its weak uricosuric action and postulated phosphaturic action.

Forty (40) female fibromyalgia patients were entered into a 12 month double blind placebo controlled study design. Subjects were randomly assigned to take either GF 600 mg. or placebo b.i.d. The major outcome measures, the FIQ and tender point score, were evaluated every 3 months. Renal tubular function was also measured.

There was no significant improvement in terms of the FIQ or the tender point score in the GF treated subjects (15.5 v 14.6). No subjects rated themselves as cured. There was no increase in the excretion of uric acid or phosphates in the GF treated group. Salicylates found in plants, cosmetics and foods are said to nullify, the efficacy of GF. Hyperuricemia and hypouricosuria were not found in any of the subjects. Thus the inadvertent use of salicylates could not have been a confounding issue this study.

Conclusion: Guaifenesin has a comparable efficacy to placebo in treating FM. The postulated physiologic action of guaifenesin on renal phosphate and urate excretion was not observed.

On 2/8/98, a participant of Fibrom-L wrote:
>>...I keep seeing mention of guaifenesin. Could someone please tell me what it is, what aspects of the syndrome it is used to treat, and what the side effects are?<<

Guaifenesin is a popular alternative medicine treatment for FMS, along with magnets, vitamins, minerals, and various herbs, but there is no scientific evidence that any of these help (by definition, "alternative" means "not scientifically verified"). Bennett's unpublished study of guaifenesin in FMS found that the rate of improvement on guaifenesin was no better than on a placebo, an inert pill. There have been no other scientific studies finding it effective.

A surprising number of patients will experience benefit from a medication just because they expect to, even if it in fact has no medicinal effect. All active medicines have this placebo effect in addition to a pharmacologic one. The placebo effect is not imaginary, but a real physical effect of a "mind over matter" sort.

The placebo effect and related sources of bias in uncontrolled studies are why scientific medical treatments need to be subjected to carefully controlled trials. These trials are what distinguishes scientific medicine from folk or alternative medicine. An initial study of the use of a liver extract and vitamins in chronic fatigue syndrome by Kaslow et al reported dramatic improvement in all patients when both the patient and the physician knew the patient was taking the active medication. When the same researchers followed this up with a randomized, controlled, double-blind study in which neither the patient nor the physician knew who was taking the medication and who was getting a placebo, they found the treatment no better than placebo. In other words, all patients reported feeling much better from the medication, yet when they didn't know whether they were taking the medication or a sugar pill, they couldn't tell the difference.

There is also evidence against St. Armand's theory of why guaifenesin works in FMS and none in support of it. He has proposed that FMS is caused by phosphate "deposits" in muscles and that guaifenesin removes these "deposits". NMR spectroscopy studies of muscles of FMS patients which found no abnormalities of muscle energy metabolism also showed no increase in phosphates. In the same study which found guaifenesin to be no better than placebo, no increase in phosphate excretion in patients taking it was seen.

St. Armand has posted elsewhere that he does not believe it necessary to test for tender points when diagnosing FMS (one of the two diagnostic criteria in the syndrome definition that everyone else studying FMS agrees upon) and he makes no distinction between FMS and myofascial pain syndrome, so it is possible that Dr. St. Armand's [patients] don't have FMS but MPS or some other disease. Perhaps guaifenesin is effective for MPS but not FMS. Another study is needed to answer this question, as Bennett only studied patients with FMS.

David A. Nye MD (nyeda@uwec.edu) * Midelfort Clinic, Eau Claire, WI

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