Guaifenesin
Cough and cold medicines
Cough and cold medicines
An expectorant that thins mucus so it is easier to cough up; it relieves chest congestion but does not treat the cause.
Also called: Glyceryl guaiacolate
Quick facts
- Group
- Cough and cold medicines
- Target
- Airway secretions (expectorant action)
- Used for
- Loosening mucus · Productive cough of acute bronchitis
- Key effects
- Nausea and vomiting · Dizziness and headache · Rash
- Monitor
- Character of sputum and ease · Fever or breathlessness
- ATC
- R05CA03
No doses: the clinician sets them by the current guideline.
Mechanism of action
Guaifenesin is thought to increase the volume and reduce the stickiness of airway secretions, partly through a reflex from the stomach that increases bronchial gland secretion. Thinner mucus is moved more easily by cilia and cough. It does not suppress cough, and the evidence for clinical benefit is modest.
- Guaifenesin stimulates a reflex from the stomach
- Bronchial glands secrete more watery fluid
- Mucus becomes thinner and less sticky
- Cough and cilia clear it more easily
Indications
- Loosening mucus in chest congestion from colds and acute bronchitis Common cold (acute viral rhinopharyngitis) →
- Productive cough of acute bronchitis Acute bronchitis →
Adverse effects
Common
- Nausea and vomiting
- Dizziness and headache
- Rash (rare)
Contraindications
- Hypersensitivity to guaifenesin
- Children under 4 years with non-prescription products
- Cough lasting more than a week, or with fever, rash or headache, needs medical review rather than self-treatment
Key interactions
- Combination products with dextromethorphan or decongestants
- Each added ingredient brings its own interactions and duplication risk
What is monitored
- Character of sputum and ease of coughing it up
- Fever or breathlessness that suggest pneumonia
Administration and safety
- Oral tablets (including extended-release, swallowed whole) and syrups
- Taken with a full glass of water; good hydration helps thin mucus
Pregnancy and breastfeeding
Data are limited, especially for the first trimester; use is decided with the clinician.
Nursing care
- Encourage fluids
- Teach that a cough with fever, rash or headache, or lasting more than a week, needs review
- Check combination products for duplicated ingredients
Pharmacokinetics
- Absorption
- Well absorbed by mouth
- Metabolism
- Liver
- Elimination
- Urine, as metabolites
Test yourself
Think of the answer, then tap the question to see it.
Is guaifenesin a cough suppressant?
No; it is an expectorant that thins mucus.
Below which age are non-prescription guaifenesin products not given?
Under 4 years.
Which simple measure supports the effect of an expectorant?
Good fluid intake.
Connections
← Back to the class: Cough and cold medicines
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Guaifenesin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2022); Use Caution When Giving Cough and Cold Products to Kids | FDA (U.S. Food and Drug Administration, 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.