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Guaifenesin

Medication expectorant cold & flu
Aka: glyceryl guaiacolate, guaiphenesin
Brands seen in Singapore: Mucinex, Breacol, Cofen 50, Guafensin, Tonin Cough Syrup S
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
Chesty cough with phlegm — thins and loosens airway mucus
When to take
Every 12 hours per the mucinex label · with or without food
Take with
A full glass of water · tablets swallowed whole, not crushed
Pros & cons
Pros
  • All 7 SG registrations are general sale list
  • HealthHub: may be taken with or without food
  • Cochrane: 1 of 3 adult guaifenesin trials was positive
Cons
  • Cochrane: no good evidence for or against otc cough
  • Drowsiness, nausea, vomiting, stomach pain, diarrhoea
  • Mucinex label: under 12 years of age — do not use
Sources
  1. HealthHub (MOH Singapore) — Guaifenesin, uses / administration / side effects (article last reviewed 16 Dec 2025) · read 2026-08-27
    what it says
    “This medication is also known as guaiphenesin. It is an expectorant that works by thinning and loosening mucus in the airways … This medication may be taken with or without food. For syrups, shake the bottle well before use.”
  2. HealthHub (MOH Singapore) — Guaifenesin, precautions and side-effect sections (article last reviewed 16 Dec 2025) · read 2026-08-27
    what it says
    “stomach ulcers, liver or kidney problems and lung conditions e.g. Chronic Obstructive Lung Disease (COPD) or severe uncontrolled asthma … a cough with thick yellow or green phlegm or mucus, or blood … Drowsiness … Nausea … Diarrhoea”
  3. MOH National Drug Formulary — MUCINEX EXTENDED RELEASE TABLETS 600MG [SIN14588P], Dosing and Contraindications · read 2026-08-27
    what it says
    “adults and children 12 years of age and over: 1 or 2 tablets every 12 hours. Do not exceed 4 tablets in 24 hours … children under 12 years of age: do not use … Forensic Classification GENERAL SALE LIST”
  4. HSA register of therapeutic products (data.gov.sg d_767279312753558cbf19d48344577084) — 7 guaifenesin rows, filtered locally 27 Aug 26 · read 2026-08-27
    what it says
    “MUCINEX EXTENDED RELEASE TABLETS 600MG … General Sale List … BREACOL COUGH SYRUP 100 mg/5 ml … General Sale List … COFEN 50 COUGH MIXTURE … GUAFENSIN SYRUP 20MG/ML … TONIN COUGH SYRUP S”
  5. Cochrane Database of Systematic Reviews — OTC medications for acute cough in children and adults in community settings (Smith, Schroeder, Fahey 2014; PMC7061814) · read 2026-08-27
    what it says
    “Three trials compared the expectorant guaifenesin with placebo; one indicated significant benefit, whereas the other two did not … There is no good evidence for or against the effectiveness of OTC medicines in acute cough”
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Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.