What is the proper dosage of guaifenesin for adults and children with varying ages and medical histories, including those with impaired renal (kidney) function or hepatic (liver) impairment?

Guaifenesin Dosing for Adults and Children

The FDA-approved dosing for guaifenesin is age-based: adults and children ≥12 years receive 200-400 mg every 4 hours (maximum 2400 mg/day), children 6 to <12 years receive 100-200 mg every 4 hours (maximum 1200 mg/day), children 2 to <6 years receive 50-100 mg every 4 hours (maximum 600 mg/day), and children <2 years require physician consultation. 1

Standard Dosing by Age Group

Adults and Adolescents (≥12 years)

• Immediate-release formulation: 200-400 mg (10-20 mL or 2-4 teaspoonfuls) every 4 hours 1
• Extended-release formulation: 600-1200 mg every 12 hours 2
• Maximum daily dose: Do not exceed 6 doses in 24 hours (2400 mg/day for immediate-release) 1

Children 6 to <12 Years

• Immediate-release: 100-200 mg (5-10 mL or 1-2 teaspoonfuls) every 4 hours 1
• Maximum: 6 doses in 24 hours 1

Children 2 to <6 Years

• Immediate-release: 50-100 mg (2.5-5 mL or ½-1 teaspoonful) every 4 hours 1
• Maximum: 6 doses in 24 hours 1

Children <2 Years

• Physician consultation required before administration 1
• Pharmacokinetic data in this age group are limited 3

Extended-Release Formulations

Extended-release guaifenesin provides 12-hour dosing convenience and is bioequivalent to corresponding immediate-release doses at steady state. 2

• Dosing: 600-1200 mg every 12 hours 2
• Food effect: Can be taken with or without food, though Tmax is delayed in fed state without affecting total exposure 2
• Advantage: Reduces dosing frequency from every 4 hours to every 12 hours while maintaining therapeutic efficacy 2, 4

Special Population Considerations

Renal Impairment

• No specific dosage adjustments are provided in FDA labeling 1
• Guaifenesin is primarily metabolized hepatically and renally excreted 3
• Use caution in severe renal impairment, though specific dose reductions are not established 1

Hepatic Impairment

• No specific dosage adjustments are provided in FDA labeling 1
• Exercise clinical judgment in severe hepatic disease 1

Pregnancy and Lactation

• Generally considered safe for short-term use 4
• Consult physician for risk-benefit assessment 1

Pharmacokinetic Considerations in Children

Pediatric pharmacokinetics show age-related changes in clearance and volume of distribution, but allometric scaling indicates no maturation-related changes requiring dose adjustment beyond weight/age-based dosing. 3

• Oral clearance and volume of distribution increase with age due to body size 3
• Terminal half-life increases with age 3
• Age-based dosing in the monograph accounts for these developmental changes 3

Clinical Efficacy Notes

• Therapeutic effect requires multiple daily doses with immediate-release formulations to maintain 24-hour coverage 4
• Flexible dose titration within the approved range (200-400 mg per dose for adults) allows optimization of plasma concentrations 4
• Most robust clinical efficacy data exist for chronic respiratory conditions with stable mucus production 4

Safety Considerations

• Well-established safety profile in both adult and pediatric populations when used at recommended doses 4
• Documented side effects are generally mild at therapeutic doses 4
• Severe toxicity (CNS depression, cardiac effects) reported only in massive overdose situations 5
• Never exceed maximum daily doses: 6 doses per 24 hours for any age group 1