What is the appropriate liquid dosage of guaifenesin for an adult and for a child (2–12 years)?

Guaifenesin Liquid Dosage

For adults, the liquid dosage of guaifenesin is 10–20 mL (2–4 teaspoonfuls) every 4 hours, not exceeding 6 doses in 24 hours; for children aged 2–12 years, the dose is 2.5–10 mL (½–2 teaspoonfuls) every 4 hours depending on age, also not exceeding 6 doses in 24 hours. 1

Adult Dosing

• Standard dose: 10–20 mL (equivalent to 200–400 mg) every 4 hours 1
• Maximum frequency: Do not exceed 6 doses in any 24-hour period 1
• Dosing flexibility: The 200–400 mg range allows titration based on symptom severity and individual response 2

Pediatric Dosing by Age

Children 6 to under 12 years

• Dose: 5–10 mL (1–2 teaspoonfuls) every 4 hours 1
• Maximum: 6 doses per 24 hours 1

Children 2 to under 6 years

• Dose: 2.5–5 mL (½–1 teaspoonful) every 4 hours 1
• Maximum: 6 doses per 24 hours 1

Children under 2 years

• Recommendation: Consult a physician before use 1
• Pharmacokinetic data in this age group are limited, and dosing should be determined by a healthcare provider 3

Important Clinical Considerations

Dosing Interval Rationale

• The 4-hour dosing interval for immediate-release liquid formulations is necessary due to guaifenesin's short half-life 4
• Multiple daily doses maintain therapeutic plasma concentrations throughout the day 2

Age-Based Pharmacokinetics

• Systemic exposure (AUC and Cmax) increases with age when using the upper recommended dose for each age group 3
• Oral clearance and volume of distribution increase proportionally with body size, with no maturation-related changes beyond allometric scaling 3
• The upper dose for children aged 2–11 years provides similar systemic exposure to the lower dose for adolescents aged 12–17 years 3

Administration Tips

• Guaifenesin liquid may be taken without regard to meals 1
• Administration with food may improve gastrointestinal tolerability in some patients 2

Extended-Release Alternative

• For patients requiring less frequent dosing, extended-release tablet formulations provide 12-hourly dosing instead of 4-hourly liquid administration 2, 4
• Extended-release guaifenesin 1200 mg every 12 hours provides equivalent steady-state exposure to immediate-release 400 mg every 4 hours 4