Guaifenesin - Drug Monograph

Introduction

Guaifenesin is an expectorant medication commonly used to relieve chest congestion by helping to thin and loosen mucus in the airways. First approved by the FDA in 1952, it remains one of the most widely used over-the-counter medications for respiratory symptoms associated with conditions like the common cold, bronchitis, and other respiratory tract infections.

Mechanism of Action

Guaifenesin works through two primary mechanisms: 1. Expectorant action: It enhances the output of respiratory tract fluid by reducing the adhesiveness and surface tension of mucus, facilitating its removal from the airways 2. Mucolytic properties: It increases the water content of respiratory secretions, decreasing their viscosity and making them easier to expectorate

The drug stimulates vagal receptors in the gastric mucosa, which reflexively increases respiratory tract secretions through the vagus nerve.

Indications

• FDA-approved: Symptomatic relief of respiratory conditions characterized by dry, nonproductive cough and difficult-to-expel mucus
• Off-label uses: May be used as adjunctive therapy in chronic bronchitis, asthma, and other conditions with thick respiratory secretions

Dosage and Administration

• 6-12 years: 100-200 mg every 4 hours (maximum 1200 mg/day)
• 2-6 years: 50-100 mg every 4 hours (maximum 600 mg/day)
• <2 years: Use only under medical supervision

• Renal impairment: No specific dosing adjustments required
• Hepatic impairment: No specific dosing adjustments required
• Elderly: Use standard adult dosing with caution regarding concomitant medications

Pharmacokinetics

• Absorption: Rapidly absorbed from the GI tract with onset of action within 30 minutes
• Distribution: Widely distributed throughout the body
• Metabolism: Primarily hepatic via oxidative O-demethylation
• Elimination: Renal excretion as inactive metabolites with elimination half-life of approximately 1 hour
• Bioavailability: Nearly complete oral bioavailability

Contraindications

• Hypersensitivity to guaifenesin or any component of the formulation
• Patients with known hypersensitivity reactions to related compounds

Warnings and Precautions

• Use with caution in patients with persistent or chronic cough (such as occurs with smoking, asthma, or emphysema)
• Not recommended for cough associated with excessive secretions
• Patients should seek medical attention if cough persists for more than 7 days, recurs, or is accompanied by fever, rash, or persistent headache
• Use caution in patients with renal or hepatic impairment (though no specific contraindications exist)

Drug Interactions

• Minimal clinically significant drug interactions
• Theoretical potential to affect absorption of other medications due to increased respiratory secretions
• No known significant interactions with cytochrome P450 enzymes

Adverse Effects

• Nausea
• Vomiting
• Gastrointestinal upset
• Dizziness
• Headache
• Rash

• Allergic reactions including urticaria
• Drowsiness (particularly with combination products containing sedating ingredients)

Monitoring Parameters

• Effectiveness of mucus clearance and cough symptoms
• Respiratory status and ability to expectorate
• Adverse effects, particularly gastrointestinal symptoms
• Compliance with hydration recommendations

Patient Education

• Maintain adequate hydration to help loosen secretions
• Notify healthcare provider if symptoms persist beyond 7 days or worsen
• Follow recommended dosing instructions carefully
• Be aware that guaifenesin is intended to make coughs more productive, not to suppress coughing
• Avoid use in children under 2 years without medical supervision
• Read combination product labels carefully to avoid duplicate ingredients

References

1. FDA Drug Monograph: Guaifenesin. Revised 2023 2. AHFS Drug Information®. Guaifenesin monograph. American Society of Health-System Pharmacists 3. Rubin BK. Mucolytics, expectorants, and mucokinetic medications. Respir Care. 2007;52(7):859-865 4. Albrecht HH, Dicpinigaitis PV, Guenin EP. Role of guaifenesin in the management of chronic bronchitis and upper respiratory tract infections. Multidiscip Respir Med. 2017;12:31 5. Micromedex® Healthcare Series. Guaifenesin drug monograph. IBM Watson Health 6. Ziment I. Management of cough and mucus hypersecretion. In: Clinical Chest Medicine. 1987;8(2):243-253