Fibromyalgia is a long-term disorder that causes musculoskeletal pain, fatigue, and areas of tenderness. The cause of fibromyalgia isn’t yet known, but it may be related to stress, infections, or an injury.

Since there’s no cure, most people with fibromyalgia seek something to ease their symptoms and improve their quality of life.

Guaifenesin, more commonly known by its brand name Mucinex, is sometimes touted as an alternative treatment for fibromyalgia. Guaifenesin is an expectorant. It thins the mucus in your air passages. For this reason, it’s most frequently used to treat chest congestion. Guaifenesin is easy to find and available over the counter.

In the 1990s, Dr. R. Paul St. Amand hypothesized that guaifenesin could be used to treat fibromyalgia because it’s mildly uricosuric. Uricosuric means it removes uric acid from the body. St. Amand believed that guaifenesin helps with fibromyalgia symptoms because it removes uric acid and phosphate from the body. The evidence supporting his claims was anecdotal, but it was enough to garner a huge following.

Guaifenesin hasn’t been shown in clinical studies to be effective for fibromyalgia, however.

The guaifenesin protocol is the treatment for fibromyalgia developed by St. Amand in the 1990s.

According to him, uricosuric drugs, such as those used to treat gout, can also relieve fibromyalgia symptoms. Guaifenesin is only mildly uricosuric. It also has fewer side effects than other uricosuric drugs. It’s inexpensive and easy to find. St. Amand decided it could be the ideal remedy.

St. Amand’s protocol includes three parts:

  1. slowly increasing (titrating) the dosage of guaifenesin until you find the right one
  2. avoiding salicylates (which are found in many medications such as aspirin, cosmetics, and herbs like St. John’s Wort)
  3. consuming a low-carbohydrate diet

The protocol says that your symptoms should actually get much worse at first. That’s how you know that you’ve reached the correct dose. Proponents claim you’ll feel worse while the drug works to remove phosphate deposits from your tissues. If you continue to follow the protocol, they say, you’ll gradually begin to feel better. Eventually, you’ll go into remission and be symptom-free.

Guaifenesin hasn’t been approved by the U.S. Food and Drug Administration (FDA) for treating fibromyalgia or any of its symptoms. This is because it hasn’t been shown to be successful in clinical trials with enough human subjects.

Despite this, the guaifenesin protocol has been embraced by many based solely on anecdotal evidence.

According to anecdotes, guaifenesin can:

  • rid the body of “harmful” phosphate deposits
  • relax the muscles
  • relieve pain
  • increase the pain-relieving effects of other pain relievers
  • reduce anxiety
  • reverse all symptoms of fibromyalgia

There has only been one randomized clinical trial done to assess the effectiveness of guaifenesin in treating the symptoms of fibromyalgia. The study included 40 women with fibromyalgia. Half of the women received 600 milligrams of guaifenesin twice a day, and the other half took a placebo (sugar pill) twice a day.

Results of the study found that guaifenesin had no significant effects on pain and other symptoms of fibromyalgia compared to the placebo over the course of a year. The study authors also found that blood and urine levels of phosphate and uric acid were all normal during the study, and no change was observed over time.

After the results were released, St. Amand stated that the study didn’t properly control for salicylate use, and that’s why it failed. He recommended a follow-up study.

However, the principal author of the study, Dr. Robert Bennett, maintains that none of the participants were using products containing salicylates during the study. Bennett believes that most of the success with guaifenesin can be attributed to a placebo effect and feeling a heightened sense of control.

St. Amand has since published a book on how guaifenesin can help people with fibromyalgia. He also began marketing a new cosmetic line that doesn’t contain salicylates.

Anecdotal reports and patient surveys continue to be highly supportive of guaifenesin. A phone survey of women who self-reported having fibromyalgia found that guaifenesin was one of the most common at-home treatments for these women. The women also rated guaifenesin as highly effective.

There is some evidence that guaifenesin has muscle relaxant properties when used at higher doses. More research is needed to confirm these effects, but this could partially explain why some people with fibromyalgia feel better while taking guaifenesin. Keep in mind that there are already FDA-approved muscle relaxants that may work better than guaifenesin.

Though St. Amand claims that guaifenesin doesn’t have side effects, this isn’t true.

Side effects of guaifenesin are usually mild. The most common are:

At high doses, guaifenesin can increase your risk of having kidney stones.

The use of guaifenesin for fibromyalgia lacks a solid scientific basis. Always talk to your doctor before beginning an unproven treatment for your condition.

During your appointment, your doctor can give their recommendations for treating your fibromyalgia symptoms, such as antidepressant medications, pain relievers, muscle relaxants, or physical therapy. You may need to try a few different treatments or a combination of treatments before you find something that works for you.

If you want to try guaifenesin for fibromyalgia, your doctor will first need to make sure it won’t interact with any other medications you’re already taking. Don’t stop taking your prescriptions without first consulting your doctor.