Cough · Expectorant
Guaifenesin
Guaifenesin is an expectorant used to help loosen and thin mucus so it can be cleared more easily from the airways.
OTCPregnancy: cautionKidney warningLiver warningAlcohol interactionSenior precautionOverview & typical uses
Guaifenesin is an expectorant used to help loosen and thin mucus so it can be cleared more easily from the airways.
Primary uses
- Chesty (productive) cough with thick mucus
- Supporting comfort during colds and mild bronchitis
How it works
Increases the water content and reduces the thickness of respiratory mucus, making it easier to cough up.
Available forms & strengths
- Tablet — 400 mg, 600 mg (Oral)
- Extended-release tablet — 1200 mg (Oral)
- Oral syrup — 100 mg / 5 mL (Oral)
General precautions & contraindications
Do not use if
- Known allergy to guaifenesin
Pregnancy
Use with caution — discuss with clinician. Limited evidence of harm; discuss with a clinician for regular use.
Breastfeeding
Use with caution — discuss with clinician. Limited data; short-term use is usually acceptable.
Kidney considerations
- No specific dose adjustment needed for routine use.
Liver considerations
- Use with caution in severe liver disease.
Paediatric use
Not recommended under 6 years.
Older adults
Drink plenty of fluids to help mucus loosen.
Common side effects
- Mild nausea or stomach upset
- Dizziness
- Drowsiness
- Headache
Serious warnings — seek help if these appear
- Serious allergic reaction (very rare)
- Kidney stones with very high prolonged use (uncommon)
Drug interactions
Additive drowsiness in some people.
Food & alcohol precautions
Drinking plenty of fluids helps guaifenesin thin mucus effectively.
Alcohol
- May increase drowsiness in sensitive individuals.
Storage, missed dose & overdose
Storage
Store below 25 °C, out of reach of children.
If a dose is missed
Take when remembered unless the next dose is near.
Overdose
Overdose is rarely serious; may cause nausea and vomiting. Seek advice for large overdoses.
Frequently asked questions
They serve opposite goals — expectorants encourage clearing mucus; suppressants reduce the cough reflex. Choose based on whether the cough is productive or dry.
Medical references
- British National Formulary — Guaifenesin — BNF (NICE)
- FDA OTC monograph — Expectorants — U.S. Food & Drug Administration
Content last reviewed: 2025-01-01
Medical disclaimer
This information is for educational purposes only and should not replace professional medical advice. Please consult a licensed pharmacist or clinician for advice tailored to your personal circumstances.