Healthy Living

Guaifenesin Drug Interactions

Guaifenesin Drug Interactions

What is guaifenesin?

It is an expectorant. It helps to cough out mucus through the mouth. It is known to reduce chest congestion caused by infections, common cold or allergies, respiratory illnesses, and bronchitis. It is not used to treat cough caused by smoking and long-term breathing problems. Guaifenesin helps in thinning the mucus and loosening it from the airways. Thus, breathing becomes easy. Children younger than 6 years old should not take cough and cold medicines unless instructed by the doctor.


Guaifenesin is taken by mouth. It can also be taken with or without a meal. Unless instructed by the doctor, do not split, crush, or chew the tablet. Do not take more than six doses in one day. The doctor will recommend the dose depending on the age, response to the treatment, and medical condition. Aside from coughing, inform your doctor if you experience other symptoms such as a severe sore throat, fever, rash, and a persistent headache.

Side Effects

The common side effects of guaifenesin are nausea and vomiting. If the symptoms do not go away or become worse, inform your doctor immediately. If you experience any allergic reactions such as skin rashes, itching, swelling of the face, throat, and tongue, severe dizziness, and a difficulty in breathing, seek medical attention right away. 

Other Side Effects

Mechanism of Action

y increasing the volume and reducing the viscosity of secretions in the bronchi and trachea. It makes the flow of secretions from the respiratory tract easy. It also enables the movement of cilia, which help carry the secretions upward. It facilitates the removal of secretions and also increases the efficiency of cough reflex.

Forms of Medications

Guaifenesin is sold in the form of syrups or pills under various brand names. It is sometimes combined with ephedrine, phenylephrine, paracetamol, and dextromethorphan. In many over-the-counter cold and cough medications, guaifenesin alone is also available.

Earlier, guaifenesin was used to treat fibromyalgia. Since studies revealed that guaifenesin was not very effective for fibromyalgia, its use was not approved by the FDA. Later, its use was studied in improving the chances of conception. A few days before ovulation, it acts by thinning and increasing the stretchability of the cervical mucus so it could facilitate the penetration of sperm cells.

Guaifenesin and Theophylline

Guaifenesin is an expectorant and theophylline is a bronchodilator. Guaifenesin loosens the mucus and makes it easier to remove by coughing it up. Theophylline increases the airflow in the chest and lungs by relaxing the muscles. The combination of both is used to treat conditions such as bronchitis, asthma, and emphysema. The possible side effects include seizures, severe nausea, vomiting, and an irregular heartbeat. The less serious side effects include skin rashes, mild nausea, weight loss, headache, dizziness, tremors, insomnia, and restlessness.

Drug Interactions

The following drugs may interact with guaifenesin and theophylline:

  • Birth control pills
  • Ciprofloxacin, erythromycin, rifampin, levofloxacin, clarithromycin, and ketoconazole
  • Interferon products such as Infergen, Betaseron, Actimmune, Intron A, Alferon N, and Avonex
  • Thyroid hormones such as levothyroxine
  • Beta blocker such atenolol, propranolol, metoprolol, and timolol
  • Calcium channel blockers such as nifedipine, verapamil, and diltiazem
  • Asthma medications such as Proventil (albuterol) and salmeterol
  • Seizure medications such as phenobarbital and phenytoin
  • Diuretic drugs

A number of medications can interact with guaifenesin and theophylline. Keep a list ready with you so that the doctor is aware of the list of medications you are already taking.

Do not take the combination of guaifenesin and theophylline f you have the following conditions:


Talk to your doctor before taking the medication. If you are allergic to guaifenesin, then it may cause allergic reactions. Inform your doctor about your medical history. Tell your doctor if you have a history of chronic bronchitis, emphysema, smoker's cough, asthma, and if you cough with a large amount of blood or mucus.

It is quite important to inform your doctor if you have liver disease, diabetes, and other medical conditions. Guaifenesin medications in the liquid or powder form may contain aspartame. Restrict its use if you have phenylketonuria, while pregnant, and before any type of surgery. Make sure that you inform the doctor about the medications that you are using. If you are breastfeeding, consult a doctor before using this medication.

Interaction with Other Drugs

Guaifenesin helps to cough up mucus through the mouth. It helps in loosening chest and throat congestion. It is also used in combination with pseudoephedrine and dextromethorphan to treat cough, sinus congestion, stuffy nose, chest congestion due to allergies, flu, and the common cold. If this medicine is used with MAO inhibitors such as linezolid, rasagiline, selegiline, isocarboxazid, phenelzine, and tranylcypromine, it may cause a dangerous drug interaction.

If over-the-counter medications are used along with guaifenesin, then it will affect its effectivity. The drug may not work properly or the risk of side effects may increase. It may also interact with the drug that you are currently taking. Hence, you should keep a list of all prescribed and non-prescribed drugs as well as herbal products you have taken and present it to the doctor or pharmacist to identify drug interactions. Do not start or stop any type of medication without your doctor's advice.

Taking other drugs or herbal products may change the effect of this drug. The risk of various side effects can increase and it may not allow the medication to work properly. Drug interactions may not always occur since they are rare. By close and frequent monitoring, the doctor may look for possible drug interactions. Do not stop or alter the dosage of this medication without informing the doctor. Guaifenesin can be prescribed or bought over-the-counter. Check the labels of all medications that you are taking. If two products contain the same ingredient, then it may cause an overdose.

Guaifenesin is an active ingredient in Mucinex and Robitussin. Sometimes, drug interactions are unlikely or it may not occur at all. However, it is marketed in combination with other active ingredients, which include cough suppressants and antihistamines. These other active ingredients may cause drug interactions. Hence, the interpretation of drug interactions should be cautiously done.

Always check the labels of cough products, especially the active ingredients present in them. There are no significant drug interactions with guaifenesin. If the medication only contains guaifenesin, the chances of drug interactions are unlikely. Sometimes, if you are taking more than one product that contains guaifenesin, there are chances that both guaifenesin may interact with each other and lead to an overdose.

There are 32 drugs known to interact with guaifenesin, including 54 major drug interactions, 263 moderate drug interactions, and 3 minor drug interactions.

  • Advair Diskus - Using guaifenesin with this drug may increase cardiovascular side effects such as an increased heart rate, high blood pressure, and irregular heartbeat. Talk with your doctor if you have a history of high blood pressure, heart disease, or irregular heartbeat. The doctor will monitor your condition and accordingly adjust the dosage, prescribe other alternative drugs, or may suggest taking both medications and safely regularly monitor your condition. Do not stop any medication without your doctor's advice.
  • Cymbalta - The combined use of Cymbalta and guaifenesin may cause an increase in the heart rate and blood pressure. Inform your doctor if you have a history of heart disease. The doctor might adjust the dosage or prescribe an alternative drug. 
  • Food or alcohol - Guaifenesin may interact with food or alcohol by altering the way guaifenesin works or by increasing the side effects associated with it. Talk with your doctor before you start taking guaifenesin to know potential food items that need to be avoided.
  • Anticoagulants or acetaminophen - The drug interaction is moderate. The combined use of both medications may cause some risks. An individual may experience an increased risk of bleeding from the nose and gums along with unusual bruising and dark stools.
  • Warfarin - This anticoagulant is taken to prevent blood clots. It is also prescribed for stroke and blood clotting disorders. However, a moderate interaction has been found between guaifenesin and warfarin.
  • Ibuprofen - There have been reports of drug interactions between guaifenesin and ibuprofen. The symptoms of drug interactions are insomnia, tremors, bronchial hyperreactivity, disorientation, and gait disturbance, among others. 
  • Guaifenesin dextromethorphan with gabapentin - The combined use of both drugs could increase the risk of side effects, which include drowsiness, confusion, difficulty concentrating, and dizziness. In the elderly, it may impair judgment, thinking, and motor coordination. People on these medications should avoid or limit the use of alcohol. Also, activities such as driving and operating heavy machinery, which requires mental alertness should be avoided. Inform your doctor about all the vitamins, supplements, and other medications that you are taking.
  • Guaifenesin dextromethorphan with trazodone - A combination of these drugs can increase the risk of a serious condition called serotonin syndrome. Although it is rare, its symptoms include extreme changes in blood pressure levels, hallucinations, excessive sweating, shivering or shaking, fever, muscle spasms, tremors, increased heart rate, stiffness, nausea, diarrhea, seizure, stomach cramps, and diarrhea. If the condition becomes severe, it may even result in coma and death.
  • Benadryl - When Benadryl is used with guaifenesin, it may increase the risk of certain side effects such as poor concentration, confusion, drowsiness, and dizziness. Some people may experience impaired motor coordination, thinking, and judgment.

The following drugs may also interact with guaifenesin:


Studies have shown that guaifenesin enhances the analgesic effects of paracetamol. Further studies were conducted to find out whether guaifenesin is also able to enhance the analgesic activity of nonsteroidal anti-inflammatory drugs (NSAIDs), which include ibuprofen, celecoxib, and nimesulide. Moreover, the effects of guaifenesin were investigated on plasma levels of nimesulide.

The study was done in mice and it was found that guaifenesin alone did not have any antinociceptive effect. However, the combination of 200 mg/kg of guaifenesin and 10 and 30 mg/kg doses of ibuprofen, 10 and 20 mg/kg of nimesulide or 1 and 5 mg/kg of celecoxib showed significant antinociceptive effects. The level of nimesulide in the plasma was found to be significantly high. Thus, the study suggested that the analgesic activity of various NSAIDs could be enhanced with guaifenesin.

Bottom Line

Guaifenesin is not known to cause any significant drug interactions, but it does cause some adverse reactions. However, the laboratory determination of 5-hydroxyindoleacetic acid (5-HIAA) and vanillylmandelic acid (VMA) may cause false readings. Guaifenesin is often mixed with ketamine, xylazine, and barbiturates. Its administration with physostigmine is cautioned, but its interaction is not explained.

Key Takeaways

  • Guaifenesin acts as an expectorant by increasing the volume and reducing the viscosity of secretions in the bronchi and trachea. It makes the flow of secretions from the respiratory tract easy.
  • Guaifenesin is not known to cause any significant drug interactions, but it does cause some adverse reactions.
  • If you experience any allergic reactions such as skin rashes, itching, swelling of the face, throat, and tongue, severe dizziness, and a difficulty in breathing, seek medical attention right away.