Mucinex (Guaifenesin) Dosing for Adults
Standard Adult Dosing
For immediate-release guaifenesin, adults and children ≥12 years should take 200–400 mg (10–20 mL or 2–4 teaspoonfuls) every 4 hours, not exceeding 6 doses in 24 hours (maximum 2,400 mg/day). 1
For extended-release formulations (Mucinex®), the standard dose is 1,200 mg (two 600 mg tablets) every 12 hours, which provides bioequivalent steady-state exposure to the immediate-release formulation dosed every 4 hours. 2
Formulation-Specific Considerations
Immediate-Release (IR)
- Dose range: 200–400 mg every 4 hours 1
- Maximum daily doses: 6 doses per 24 hours 1
- Flexibility: The dosing range allows titration to increase plasma concentrations as needed 3
- Limitation: Multiple daily doses required to maintain 24-hour therapeutic effect 3
Extended-Release (ER)
- Standard dose: 1,200 mg every 12 hours 2, 4
- Advantages: Convenient 12-hour dosing with portability compared to liquids 3
- Food effect: AUC and Cmax remain equivalent whether taken fasted or fed, though Tmax is delayed in the fed state 2
- Duration: Typically prescribed for 7 days in acute upper respiratory tract infections 4, 5
Renal and Hepatic Impairment
No dose adjustment is required for guaifenesin in moderate renal or hepatic impairment. Guaifenesin is a BCS class I drug with high water solubility and is primarily metabolized and excreted without significant accumulation in organ dysfunction. 6 The FDA label provides no specific warnings or dose modifications for renal or hepatic disease. 1
This contrasts sharply with nephrotoxic expectorants or mucoactive agents (such as aminoglycosides used in respiratory infections), which require dosing frequency reduction to 2–3 times weekly in renal impairment. 7
Safety and Tolerability Profile
- Adverse events: In a post-marketing study of 552 adults taking ER guaifenesin 1,200 mg every 12 hours for 7 days, only 28 patients (5.1%) experienced treatment-emergent adverse events, all mild in severity 4
- Common side effects: Gastrointestinal (n=11), nervous system (n=8), and psychiatric symptoms (n=3) were most frequent 4
- No serious adverse events or deaths occurred in clinical surveillance 4
- Well-established safety in both adult and pediatric populations 3
Clinical Efficacy Timing
The most prominent symptom improvement occurs by Day 4 of treatment, as demonstrated in randomized controlled trials comparing guaifenesin 1,200 mg every 12 hours to placebo. 5 The composite SUM8 diary score (8 symptom-related questions) showed the strongest treatment effect at this timepoint. 5
Common Pitfalls to Avoid
- Do not exceed 6 doses per day of immediate-release formulations (maximum 2,400 mg/24 hours), as per FDA labeling 1
- Do not assume dose adjustment is needed in renal or hepatic impairment—standard dosing applies 1
- Do not switch between IR and ER formulations without adjusting the dosing interval (every 4 hours vs. every 12 hours) 2, 3
- Do not expect immediate symptom relief—peak efficacy typically occurs around Day 4 of treatment 5