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Guaifenesin and Drowsiness: What Users Say

Brand names: Mucinex, Mucinex Maximum Strength, Humibid, Breonesin, Tussin Expectorant, Robafen, Family Meltus Chesty Coughs, Fenesin, Guaiatussin, Organ-1 NR, Scot-Tussin Expectorant, Guiatuss, Altarussin, Diabetic Tuss, Guiadrine G-1200, Xpect, Junior Meltus Chesty Coughs with Catarrh, Dristan Chesty Cough Guaiphenesin, Benadryl Chesty Forte, G Bid, Ganidin NR, Humibid Pediatric, Mucinex Children's Chest Congestion, Guaibid-LA, Aquamist, Amibid LA, Mucobid-LA, Guaifenex LA, Fenex-LA, Rompe Pecho EX, Guaifenesin LA, Humavent LA, Guiacough, GG 200 NR, Glytuss, Anti-Tuss, Diabetic Expectorant, Allfen Jr, Genatuss, Siltuss DAS, Gua-SR, Humigen LA, Altorant, Duratuss G, Robitussin Mucus + Chest Congestion, Guaifenex G, GG-Cen, Benylin E Calmylin Expectorant Siltussin DAS-NA Balminil Expectorant Drituss G Beechams Veno's for Kids Chesty Cough Junior Meltus Colour and Sugar Free Expectorant Help I Have Chest Congestion Bidex-400 Humibid E Fenesin IR Hill's Balsam Chesty Cough Beechams Veno's Expectorant Lemsip Cough Chesty Dristan Chesty Cough Mucinex for Kids Guaifen NR Buckley's Chest Congestion TabTussin 400 Siltussin DAS Diabetic Tussin Mucus Relief Refenesen Chest Congestion Relief Bronchoril Hytuss Mucaplex Tussin Mucus + Chest Congestion Air Power Diabetic Tussin Chest Congestion Giltuss EX Expectorant Giltuss Children's EX Expectorant …show all brand names

Drowsiness: mentioned by 12 users (3.9%)

Based on user experiences from 305 Guaifenesin reviews, the following table shows the most commonly mentioned side effects.

All user comments are moderated by Drugs.com. Each review is verified for relevance and screened for inappropriate content. Side effects are user-reported and not clinically verified.

nausea 4.9%
dizziness 4.6%
cough 3.9%
drowsiness 3.9%
pain 3.3%
vomiting 2.6%
diarrhea 2.3%
headaches 2.3%
insomnia 2.0%
upset stomach 2.0%

Reviews for Guaifenesin

Showing 12 reviews tagged with "drowsiness". Clear filters to view all 305 reviews.
Commonly mentioned side effects
  • Anonymous
  • October 13, 2009

Mucinex (guaifenesin) for Bronchitis "First time Mucinex DM user. I like the extended relief because it really does provide extended relief from the severe coughing that is characteristic of bronchial infections. The medication did make me a little drowsy, so some caution is recommended especially if you are not able to take time off to rest. I also recommend drinking lots of fluid too. You may notice that your urine smells like the medication."

9 / 10
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119 Report
  • jim...
  • October 15, 2014

Mucinex (guaifenesin) for Cough "After all the treatments I had from the doctor, nothing really suppressed the cough, which I have had for years. After taking Mucinex, my cough and the associated phlegm have almost disappeared. I am a 74-year-old male, but my side effects seem to be the opposite of others, i.e. I am doing more sleeping than normal, at any time night or day, but thank heavens for the cessation of cough."

9 / 10
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90 Report
  • Anonymous
  • November 7, 2011

Mucinex (guaifenesin) for Cough "About an hour and a half after taking one Mucinex DM, I developed severe dizziness, drowsiness, bad intestinal cramps, vomiting, and diarrhea that recurred over a period of 2 hours. It was the only medication in my system."

1 / 10
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54 Report

Frequently asked questions

  • Jan...
  • Taken for 5 to 10 years
  • April 4, 2020

Robafen (guaifenesin) for Bronchitis "Have your local compounding pharmacy order you the pure guaifenesin syrup. You do not want the kind in the drugstore because it contains dextromethorphan ... which is probably what others have described as making them sick or drowsy. The brand my pharmacy gets for me is Robafen syrup. You can get a pint for about $8. I have COPD and have used it for years. Robitussin used to make the plain stuff, but I haven't seen it in the stores for a long time. Although it says only take 6 times daily. It's much more soothing to the throat than Mucinex pills and works instantly to get the phlegm out of your lungs. I couldn't live without it!"

9 / 10
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  • tom...
  • Taken for less than 1 month
  • September 23, 2021

Mucinex (guaifenesin) "I took this for muscle pain and soreness, which is a common off-label use recommended by my doctor. While it was pretty effective for relaxing muscles, it caused very bad sleeplessness, even when taking an Ambien. I had to stop use, as insomnia made the muscle pain worse! Catch-22..."

3 / 10
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4 Report

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  • Bri...
  • February 3, 2015

For Cough "Recently, I had a horrible head cold, it wasn't serious enough to see a doctor, so I started taking Mucinex D. The second day I took the pill, I noticed I was on the drowsy side, and my urine was foul-smelling. I took it for three days, about two hours into taking the third pill, I started to get leg cramps and horrible abdominal pains that lasted for almost another 24 hours. The pain was awful and made me very nervous. My cold symptoms had subsided, so yes, it does work, but the side effects were awful."

8 / 10
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  • bj ...
  • September 23, 2014

For Cough "I'm to take it regularly. I soon found out that it makes my urine smell. While that may not be too bad a deal, it also seems to make me slightly incontinent. A bad combination. It also generally makes me weak and drowsy."

7 / 10
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8 Report

More FAQ

  • dre...
  • Taken for less than 1 month
  • February 6, 2025

"I took this medicine for the first time last night after weeks of dealing with horribly thick sinus drainage that was making my throat hurt and making it hard to sleep. This medication was amazing! I took the 12-hour extended-release 1200 mg version (Equate brand from Walmart). I wasn't sure what to expect, but I was very pleased. I'm writing this review the next day and still feel the benefits. My only regret is that I waited so long to try it. I was under the mistaken belief that it was only for chest congestion, which I didn't have, but it seems to work great for me for the nose/throat/ear congestion. The main side effect for me was sleepiness, but since I took it at night, that wasn't a problem. I did also seem to have some frequent urination, getting up three times in the night when I'm usually only up once. Worth it!"

9 / 10
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  • Anonymous
  • August 29, 2009

Mucinex (guaifenesin) for Bronchitis "This is the only medicine that helps loosen nasal mucus without the side effects like sleepiness or jitters that most of the sinus medications give me. It's great!"

9 / 10
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62 Report
  • Dil...
  • Taken for less than 1 month
  • July 17, 2014

Mucinex (guaifenesin) for Cough "The side effect was sleeplessness. First night, I was up until 4:00 AM, next night up until 07:00 AM, and again last night I could not sleep. I was taking the Mucinex as prescribed every 12 hours."

8 / 10
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42 Report
  • agr...
  • December 31, 2014

Mucinex (guaifenesin) for Cough "My cough was so bad that I now have an umbilical hernia, but the Mucinex worked. I only took it in the morning because it did cause sleeplessness."

9 / 10
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  • Sol...
  • March 17, 2020

Mucinex (guaifenesin) for Bronchitis "I took Mucinex about a month ago, and it had me sleeping all day, extra, extra tired with a slight fever. It's not my thing."

1 / 10
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Reviews may be edited to correct grammar/spelling or remove inappropriate content. Reviews appearing to come from parties with a vested interest are not published. This information is not intended to endorse any medication and should not replace the expertise and judgment of healthcare professionals.