What's the deal with guaifenesin (expectorant)?

How does it make any sense to take a cough suppressant (like dextromethorphan) AND an expectorant (guaifenesin) at the same time? Often they’re even in the same bottle. Isn’t this contradictory? Either you want to thin the secretions and then cough them up, or you instead want to suppress a cough, a dry, non-productive cough in the late stages of a URI. No?


Good question. Some people don’t know what they need to get for their symptoms, so an expectorant/cough suppressant combination may seem to be beneficial. The most popular combo product on the market is Robitussin DM, which has dextromethorphan 15 mg (cough suppressant) and guaifenesin 100 mg (expectorant) per teaspoonful. Guaifenesin does not exert much effect as an expectorant unless you take at least 1000 mg (1 g) per day, so that means for most people that product is not beneficial as an expectorant. Guaifenesin is mostly over-rated, it is pretty much only used when you have bronchitis-like symptoms to try to break up chest mucus. It’s available as a stand-alone OTC product called Mucinex (guaifenesin 600 mg given 2 tabs twice a day). It is sometimes recommended for COPD patients, but has never been shown to actually help all that much (especially for pt’s with severe secretory problems such as cystic fibrosis).

I read about a study done years ago on this very subject. They divided cough sufferers into three groups. One group was given the expectorant only. Another group was given no expectorant but was advised to force fluid intake greatly. The third group took expectorant and forced fluids.

The combo patients and the fluid only patients experienced equal reductions in phlegm viscosity. The expectorant only patients showed no significant change in phlegm viscosity.

In general, you want to cough up any gunk in your lungs. That stuff is just a fertile breeding medium for secondary bacterial infections. To that end, drinking plenty of fluids is the ticket. However, a lot of coughing is non-productive, bronchial irritation coughing which is just annoying, painful, exhausting and sometimes damaging. A good cough suppressant (or, more effective) an asthma inhaler (like albuterol) will reduce the nuisance cough but will not suppress the cough induced by a big gob of mucous.

Two years ago, my doc prescribed just guaifenisin (lots of it) to treat a sinus problem. It triggered a tremendous flow of snot. I couldn’t go 5 minutes without blowing my nose. His method was to flush out the guilty viruses. I felt much better after a few days.

Thanks to you all for answering. Questions remain. My wife has had a cough following a cold for over 3 weeks now, neg. chest xray, doc prescribed the corticosteroid inhaler Azmacor plus some benzonatate non-narc cough suppressant. Nothing works, she coughs all night and all day. No fever or any other symptoms at all. The only thing that worked was the codeine syrup, but she ran out after a week (supposedly six weeks’ supply–one teaspoon doses didn’t cut it since she had been on codeine pain meds for a year post-trauma and just stopped all narcotics a month ago). I understand the resistance to prescribing narcotics, but at this point the cough sems self-regenerating, with the airway irritation causing more coughing. About 20% of the time, some mucus is expectorated. The other 80% is just a non-productive cough.

Should a person ever take both an expectorant AND cough suppressant simultaneously, or should the guaifenesin be taken alone and the person be allowed to hack and hack to try to remove the sludge? (Thanx for the extra data about the 1000mg dose).

If I saw a patient who had three weeks of severe cough, with some relief from codiene syrup, I would consider the following:

  1. It makes sense to give a cough suppresssant, even with an expectorant, to allow the person to sleep at night time. I routinely prescribe codeine with an expectorant (e.g. CoActifed with expectorant) for this purpose on the understanding that, in theory, cough suppressant is to be given just at night time to aid sleep. If the patient (and their family!) does not sleep well, this may worsen the patient’s mood and their ability to work, even to fight off the infection. Expectorants can be given more frequently. DESPITE this neat theory, some patients say they do better with both cough suppressant and expectorant taken at the same time several times a day, plus bedtime. Coughing a lot can cause a lot of muscle (diaphragm, abdomen) irritation.

  2. Such a cough may involve allergies/asthma or brochospasm. It would be reasonable to measure “peak flow rates”. I would consider adding a Ventolin puffer to see if it helps the cough.

  3. Antibiotics are often helpful, even in the absence of a positive x-ray. Many MDs overprescribe antibiotics. I think it would be reasonable to try ONE antibiotic if the symptoms have gone on longer than two weeks. I see lots of patients whose doctors try to avoid prescribing an antibiotic at all costs. This is commendable; however many of these patients (who come to the emergency room after 3 weeks of frustration) get better quickly after one is prescribed. The first-line choice would be erythromycin 250-500mg TID for seven days. I feel Zithromax and Biaxin have a similar spectrum, but prescribe them much less.

3b.) A cough lasting more than three weeks should raise suspicions of pertussis (whooping cough), particularly if the cough is severe enough to cause vomiting. Erythromycin is the first line treatment. This can be tested for with a nasopharyngeal swab.

4.) I might consider a sputum culture if the cough lasts so long.

This may be pointing out what you find blindingly obvious, but have you/she tried cough drops? I frequently have extended periods of non-productive coughing after any minor illness, and I swear by Ricola. It doesn’t cure anything, of course, but it can sooth your throat enough to break the irritation-coughing-more irritation feedback loop. It breaks the cycle long enough for me to get to sleep. YMMV.


Thanks Dr P–Thanks for your detailed reply. My wife finally saw a pulmonologist today, after a 1-week course of methylprednisolone produced complete cessation of symptoms, which returned two days after the course ended. Her sleep was ruined as well as her mood, as you mentioned. He did the spirometry you suggest and found her lung function to be reduced 60% below normal, then prescribed some steroid inhalers and more codeine syrup. I like your idea of a nasopharyngeal swab to determine presence of bacteria–before going with an antibiotic. Maybe in her case, since she has no other symptoms of infection, he went straight to cough suppression with a diagnosis of post-viral “reactive airways” (aka “asthma,” but the ins. co. reportedly gets reactive in its own way if that term is seen).

Mischievous–Thanks for the reply, though if Ricola (“candy” according to wrapper) could quell a cough where mega-doses of dextromethorphan and codeine still leave a person barking like a seal in heat, we could save a lot of money, time and misery indeed! Plus they’re tasty.

Yes, I really only meant to say that they are useful for minor coughs which are continually re-irritated by the coughing itself. If there is an actual disease process still going on, which it sounds like there is for your wife, then they don’t help much. However, they are tasty.


One reason why guaifenesin is commonly combined with dextromethorphan is to reduce abuse of dextromethorphan. For those who don’t know the full truth about dextromethorphan, I invite you to read about it at a website I own and run all about that drug:


Dextromethorphan (DXM) is also an extremely powerful psychedelic drug. It is in the subclass of psychedelics called “dissociative anaesthetics”. The other 2 dissociative anaesthetics that have often been used recreationally are PCP (phencyclidine) and ketamine.

Selling a powerful psychedelic drug OTC, which can even be bought easily by children, is obviously problematic. One way to minimize abuse is to add in other ingredients to DXM preps that make attempted abuse unpleasant. Guaifenesin in high doses tends to be very nauseating. Adding guaifenesin to a DXM cough prep thus will discourage abuse. In fact, I am aware of at least several countries in the world where there are no OTC preps with just DXM as the active ingredient available. This was done specifically to reduce the amount of DXM abuse. Also, the lethal dose of guaifenesin is pretty astronomical. It is practically impossible for someone to harm themselves with a guaifenesin overdose. Thus, if someone takes an OD of a DXM + guaifenesin cough prep, all that guaifenesin won’t hurt them. It’ll just make them feel really sick. Which is exactly what the Powers That Be want to happen to folks who try to trip on DXM.

Thanks for sharing that, rfgdxm. I’m saving your link.

I’ve a small circle of friends who are also recovering (like me) from DXM abuse along with the more traditional alcohol, fentanyl, morphine, and the like. And I’ve also had the unfortunate circumstance of warning a recovering friend of mine to not use DXM cough syrup as he could jeopardize his recovery. Well, eventually he decided he just had to try DXM! Wham, bam, back into rehab with a whole lot more problems than before.

Small world that off all places here would be a recovering DXM abuser. Before I got on the Internet in 1997, I had thought that DXM abuse would be quite rare. Based on my own experiences using DXM. Over a decade ago I had somewhat of an abuse problem with opiates, which resulted from some chronic pain problems I had at the time. Searching through medical journal articles, I found one that suggested DXM was half as effective as codeine on a mg basis as a pain killer. After a little more (poorly done) research, I found that the lethal doses of DXM were quite high. Thus I decided to experiment with DXM. I found it useless for pain. However, to my total shock I discovered it was a psychedelic drug. I went back to the med school library and found that DXM was known to be a psychedelic. I then started using DXM specifically as a psychedelic. As a psychedelic I found it quite interesting (and, somewhat frightening.) However, the side effects profile of DXM for me is quite nasty. Such as severe diarrhea, and feeling very lethargic for the next few days. Based on these side effects, I doubted many would actually get hooked on DXM.

When I got on the Internet, I found I was in error. :frowning: I’ve received a huge amount of e-mails from people who managed to get severely hooked on DXM. Most of them have far less side effects than me. And, they find the mental effects of DXM extremely appealing. It’s not they get physically hooked (although this happens.) It is just that the DXM trip is so pleasing to their mind that they keep using it again and again. Must be the way their brains are wired.

And to anyone reading here, DO be aware that dorking around with DXM is risky business. I just added a news report to my site last month about yet another DXM abuse death. :frowning: As this wasn’t covered by the commercial press, after getting a lead I had to directly phone the coroner to confirm this person died from DXM. And after getting a copy of the coroner’s report, including a very detailed physical autopsy report, had to do a news report on his death under my own byline. Don’t be mislead by the fact that DXM is legal and sold in grocery stores that it isn’t a powerful, and potentially dangerous drug. YOU HAVE BEEN WARNED.

My experience with guaifenesin was horrible - any time I’d take it, my bronchitis would get much worse. The extra mucus is more than I can clear from my airways.

I have a chronic case following chemical exposure 20 years ago. I think allergies, atmospheric ozone, and change of weather exacerbate it. The method my pulmonologist and allergist have found works is Advair 500, Singulair, Clarinex, Beconaise, desensitization shots, plus carbon/permanganate/HEPA filters at home and in the office, all 365 days per year, plus Prednisone 40 mg/day and codeine during acute symptoms (which is about 8 months per year), plus Zithromax if fever and other signs of bacterial infection, or Levaquin if the Zithromax doesn’t stop the infection. Doing all this is like a part time job.