Mucinex is one of the more common brand names of guaifenesin. It is an over-the-counter medication used to break up and expel phlegm from the lungs. The phlegm or mucus is thinned by Mucinex. It is available as a pill, a capsule, a syrup and a solution. It also is available in extended-release pill or capsule form.
Nausea
While it is not usually serious, Mucinex can cause nausea and vomiting. According to the Mayo Clinic, this usually will go away on its own after you acclimate to it. In general, feeling nauseated or vomiting from the medication does not require medical attention. If it persists, however, contact your physician.
Diarrhea
Any medication can potentially throw your body system off. Mucinex may rarely produce diarrhea as a side effect. Aside from the direct effect of stomach cramps and loose stools, diarrhea also can dehydrate your body. If you have diarrhea, replenish your fluids by drinking water and sports drinks that contain electrolytes. Diarrhea associated with Mucinex should end in a few days. If it does not, consult your doctor.
Dizziness
Mucinex may rarely produce dizziness. This is a rare side effect. When it occurs, it can throw you off balance and cause you to be a bit clumsy. It generally is mild and will go away on its own as you get used to the medicine. If not, call your doctor.
Headaches
Mucinex may be used for symptoms associated with the flu or a cold, but it does not contain medication for aches and pains. Instead, it may give you a headache. You can remedy this malady by taking over-the-counter analgesics such as ibuprofen (Advil or Motrin), acetaminophen (Tylenol), acetylsalicylic acid (aspirin) or naproxen sodium (Aleve, Naprosyn). According to RxList.com, no drug interaction problems have been associated with Mucinex.
Rash or Hives
Guaifenensin also may produce a skin rash or hives. This may include urticaria or chronic hives. Hives appear as red and raised welts that may be itchy on the skin. While a simple rash or hives may go away in a few days, urticaria may remain longer than six weeks or return. If you cease taking Mucinex and the condition does not disappear, it may be treated by oral antihistamines such as Claritan (generic: loratadine), Clarinex (generic: desloratadine) or Zyrtec (generic: cetirizine), among others.
