Long-Term Study of Extended-Release Guaifenesin Shows Symptom Relief in Stable Chronic Bronchitis Patients

Findings presented at CHEST from the 12-week real world evidence GASP Study underscore clinical relevance, patient satisfaction, and quality-of-life gains, supporting adjunctive use of Mucinex^® (extended-release guaifenesin) in chronic respiratory care.

PARSIPPANY, N.J., Oct. 20, 2025 /PRNewswire/ -- Reckitt, the maker of Mucinex^®, the #1 physician-trusted cough and cold brand*, announced new outcomes from the Guaifenesin Assessment of Satisfaction for Patients (GASP) Study, the first long-term evaluation of extended-release (ER) guaifenesin (Mucinex) at 1200 mg twice daily (2,400 mg) over 12 weeks in patients with stable chronic bronchitis (SCB). The findings demonstrate clinically meaningful reductions in cough and sputum severity, improved quality of life impact, and high patient satisfaction, offering clinicians new real-world evidence to inform adjunctive management strategies for chronic mucus-related respiratory disease.

Historically, guaifenesin data in chronic respiratory care has been limited to short-term (≤14-day) use. The GASP Study, an investigator-initiated study (IIS) conducted under the direction of Dr. Selwyn Spangenthal and funded via a grant by Reckitt, addresses this critical evidence gap, showing sustained symptom improvement using the Cough and Sputum Assessment Questionnaire (CASA-Q), a validated patient-reported outcome measure (PROM). Improvements exceeded the minimal clinically important difference (MCID) across all domains, signaling measurable benefits in health-related quality of life (HRQoL).

Mucinex 12-Hour is indicated to thin and loosen mucus in patients with stable chronic bronchitis, helping to make coughs more productive and ease chest congestion. "For patients living with persistent cough and sputum burden, especially those with chronic bronchitis, long-term symptomatic relief is a significant unmet need," said Dr. Selwyn Spangenthal, principal investigator, and respiratory clinician. "This data reinforces the potential role of guaifenesin ER as a supportive therapy that is both effective and well-tolerated over a daily ongoing treatment period."

The 12-week, GASP Clinical Study was conducted as an open-label, single-cohort investigation evaluating daily use of guaifenesin ER (2,400 mg) in adults aged 40 years or older with stable chronic bronchitis. Patients continued their standard maintenance therapies while symptom severity and quality of life impact were measured weekly using the validated CASA-Q patient-reported outcome tool. This pragmatic design allowed researchers to assess long-term effectiveness, adherence, tolerability, and quality-of-life impact in a real-world setting.

Key findings include:

• Sustained Symptom Reduction: Daily administration of 2400 mg guaifenesin ER produced continuous reductions in cough and sputum symptoms over 12 weeks.
• Clinically Meaningful Outcomes: CASA-Q scores consistently surpassed the MCID threshold 3 weeks after starting treatment across all domains, showing significant impact on patient function and daily quality of life.
• High Patient Adherence and Satisfaction: > 90% of Participants reported treatment compliance weekly, supporting feasibility and commitment to long-term adjunctive use in SCB management.
• Strong Symptom Correlation: Analysis showed a near-perfect correlation (r=0.98) between cough and sputum domains, reinforcing mucus management as a driver of overall symptom relief.

These findings provide clinicians with:

• An evidence based daily long-term dosing strategy for chronic symptom management and foundation for integrating guaifenesin ER as an adjunctive therapy
• A PRO-based framework (CASA-Q) to track treatment benefits and functional improvement

Data from the GASP Study was shared at the CHEST 2025: Advancing Excellence and Innovation conference, hosted in Chicago on October 20th, 2025. The study results have also been accepted or presented at other major scientific forums including the London Cough Conference, ATS and American Cough Conference with further presentations scheduled at ISOQOL and GOLD International COPD conference. Abstract publications is pending in leading respiratory journals.

"At Reckitt, we believe that meaningful innovation in respiratory health begins with a deep understanding of patient needs and real-world outcomes," said Tim Shea, Senior Medical Scientist, Respiratory Research and Development. "The GASP Study represents a significant step forward in addressing a long-standing evidence gap in chronic bronchitis management—specifically, the long-term use of extended-release guaifenesin (Mucinex®) as an adjunctive therapy." For more information about the GASP study, visit Research and Clinical Studies

Dr. Selwyn Spangenthal is Board Certified in Internal Medicine and Pulmonology and is a Certified Physician Investigator through the Association of Clinical Research Professionals (ACRP). He studied medicine at the University of Cape Town, South Africa and attained MRCP (Member of the Royal College of Physicians) in London, United Kingdom. His Pulmonary fellowship was done at Tufts New England Medical Center, 1980-1982. Dr. Spangenthal has been the Principal Investigator on numerous Clinical Research studies since 1987. A great number of these drugs are now FDA approved and readily available for patient care worldwide. Dr. Spangenthal is the leading physician at American Health Research.

About Mucinex
For more than 20 years, Mucinex has helped consumers breathe easier with trusted relief from cough, chest congestion, and mucus. As the number one selling cough and chest congestion brand, Mucinex offers a range of 12-hour products that work to thin and loosen excess mucus, relieve chest congestion, and control coughing. The Mucinex 12-Hour line, including Mucinex DM for cough and chest congestion and Mucinex SE for chest congestion, provides powerful, long lasting relief day or night.

Mucinex has provided consumers with world-class mucus and congestion relief, and it is #1 in more categories than you can imagine:

• The #1 most trusted brand among physicians for cough and cold symptoms*
• The #1 most trusted brand among respiratory specialists for cough and cold symptoms**
• The #1 most trusted brand among physicians for their own family's cough & cold symptoms***

For more information, visit Mucinex.com.

About Reckitt
We make the products people trust to care for the ones they love. We are home to some of the world's best-loved consumer health and hygiene brands, including Dettol, Durex, Finish, Gaviscon, Harpic, Lysol, Mucinex, Nurofen, Strepsils, Vanish and Veet. Consumers are at the heart of everything we do. By creating innovative, science-backed solutions, we support people every day to live healthier lives.

Reckitt**** exists to protect, heal, and nurture in the pursuit of a cleaner, healthier world. This commitment goes beyond the products we make. Through our actions, we expand access to healthcare, education, and economic opportunities. We support the planet by reducing waste, conserving resources, and driving sustainable innovation.

We believe good health starts at home. With every action we take, we strive to make our consumers' lives easier, cleaner and healthier, to strengthen communities and to create a more sustainable future.

Find out more or get in touch with us at www.reckitt.com/us.

* IQVIA, ProVoice Survey, fielded to 3,930 physicians, September 1-December 31, 2024
** IQVIA, ProVoice Survey, fielded to 570 respiratory specialists, September 1-December 31, 2024
*** IQVIA, ProVoice Survey, fielded to 3,930 respiratory specialists, September 1-December 31, 2024
****Reckitt is the trading name of the Reckitt group of companies

SOURCE MUCINEX