Guaifenesin is an ingredient in cough and cold medicines that is used to help clear mucus or phlegm from your chest when you have had a cold or flu. Guaifenesin works by making your mucus thinner and easier to cough up, which helps clear chest congestion. Guaifenesin is available as an over-the-counter (OTC) medicine and also available on prescription.
Guaifenesin is not FDA approved for treatment of fibromyalgia, but some people take it off-label for this condition. In clinical studies guaifenesin has not shown to be effective for fibromyalgia.
How should I take guaifenesin?
Use guaifenesin exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended. Cough medicine is usually taken only for a short time until your symptoms clear up.
Take guaifenesin with food if it upsets your stomach.
Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.
Do not crush, chew, break, or open a controlled-release, delayed-release, or extended-release tablet or capsule. Swallow it whole. Breaking or opening the pill may cause too much of the drug to be released at one time.
Drink extra fluids to help loosen the congestion and lubricate your throat while you are taking this medication.
Store at room temperature away from moisture, heat, and light.
Usual Adult Dose for Cough:
Immediate release formulation: 200 to 400 mg orally every 4 hours as needed, not to exceed 2.4 g/day
Sustained release formulation: 600 to 1200 mg orally every 12 hours, not to exceed 2.4 g/day
Usual Pediatric Dose for Cough:
Immediate release formulation:
less than 2 years: 12 mg/kg/day orally in 6 divided doses
2 to 5 years: 50 to 100 mg orally every 4 hours as needed, not to exceed 600 mg/day
6 to 11 years: 100 to 200 mg orally every 4 hours as needed, not to exceed 1.2 g/day
12 years or older: 200 to 400 mg orally every 4 hours as needed, not to exceed 2.4 g/day
Sustained release formulation:
2 to 5 years: 300 mg orally every 12 hours, not to exceed 600 mg/day
6 to 11 years: 600 mg orally every 12 hours, not to exceed 1.2 g/day
12 years or older: 600 to 1200 mg orally every 12 hours, not to exceed 2.4 g/day
Get emergency medical help if you have signs of an allergic reaction to guaifenesin: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Common guaifenesin side effects may include:
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.