GUAIFENESIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for GUAIFENESIN (GUAIFENESIN).
Guaifenesin is an expectorant that increases respiratory tract fluid secretion and reduces mucus viscosity, facilitating expectoration.
| Metabolism | Primarily hepatic via oxidation and demethylation; major metabolite is beta-(2-methoxyphenoxy)lactic acid. CYP450 enzymes not significantly involved. |
| Excretion | Renal: ~95% (primarily as unchanged drug and glucuronide conjugate); biliary/fecal: minimal (<5%) |
| Half-life | Terminal elimination half-life: 3-5 hours; clinical context: requires dosing every 4-6 hours for sustained mucolytic effect |
| Protein binding | ~50% (bound to albumin) |
| Volume of Distribution | ~1 L/kg; clinical meaning: extensive distribution into extravascular tissues, including respiratory secretions |
| Bioavailability | Oral: 80-85% (first-pass metabolism minimal) |
| Onset of Action | Oral: 30-60 minutes after administration |
| Duration of Action | 4-6 hours; clinical note: maximal effect at peak plasma concentrations (1-3 hours post-dose) |
Oral: 200-400 mg every 4 hours as needed, not to exceed 2400 mg/day.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | No specific guidelines; use caution in severe impairment due to potential accumulation of metabolites. |
| Liver impairment | No adjustment required for mild to moderate impairment; insufficient data for severe impairment. |
| Pediatric use | Children 2-5 years: 50-100 mg every 4 hours, max 600 mg/day; 6-11 years: 100-200 mg every 4 hours, max 1200 mg/day; ≥12 years: same as adult. |
| Geriatric use | No specific adjustment; use lowest effective dose due to increased sensitivity and risk of adverse effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for GUAIFENESIN (GUAIFENESIN).
| Breastfeeding | Excretion into breast milk is likely minimal; M/P ratio not established. AAP considers compatible with breastfeeding; avoid excessive doses. |
| Teratogenic Risk | Insufficient human data; animal studies show no evidence of fetal harm. Generally considered low risk across all trimesters, though use in first trimester should be cautious due to lack of robust data. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to guaifenesin or any component of the formulation.
| Precautions | Use with caution in patients with persistent or chronic cough (e.g., smoking, asthma, COPD); if cough persists >7 days or recurs, or with fever/rash/headache, discontinue and evaluate. |
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| No specific monitoring required beyond routine prenatal care. |
| Fertility Effects | No adverse effects on fertility reported in animal or human studies. |