MUCINEX DM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MUCINEX DM (MUCINEX DM).
Guaifenesin increases respiratory tract fluid secretion to reduce mucus viscosity; dextromethorphan acts on sigma-1 receptors and NMDA receptor antagonism to suppress cough reflex.
| Metabolism | Guaifenesin undergoes hepatic metabolism via oxidation and conjugation; dextromethorphan is metabolized by CYP2D6 to dextrorphan, an active metabolite. |
| Excretion | Guaifenesin: renal (primarily as inactive metabolites, <1% unchanged). Dextromethorphan: renal (as unchanged drug and metabolites, including dextrorphan). Approximately 80% eliminated in urine as metabolites. |
| Half-life | Guaifenesin: 1-3 hours. Dextromethorphan: 3-30 hours depending on CYP2D6 phenotype; extensive metabolizers 3-8 hours, poor metabolizers 15-30 hours. |
| Protein binding | Guaifenesin: approximately 30% to albumin. Dextromethorphan: approximately 50% to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Guaifenesin: 0.8-1.5 L/kg. Dextromethorphan: 5-10 L/kg (extensive tissue binding). |
| Bioavailability | Oral: Guaifenesin ~100% (tablet/syrup). Dextromethorphan ~11% (extensive first-pass metabolism; varies with CYP2D6 phenotype). |
| Onset of Action | Oral: Guaifenesin 30 minutes; Dextromethorphan 15-30 minutes. |
| Duration of Action | Guaifenesin: 4-6 hours. Dextromethorphan: 3-6 hours for antitussive effect. |
| Molecular Weight | Guaifenesin: 198.22 Da; Dextromethorphan: 271.4 Da |
One tablet (guaifenesin 600 mg / dextromethorphan HBr 30 mg) orally every 12 hours, not to exceed 2 tablets in 24 hours.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | CrCl 30-50 mL/min: administer every 24 hours. CrCl <30 mL/min: not recommended. Hemodialysis: not recommended. Peritoneal dialysis: not recommended. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50% or extend interval to every 24 hours. Child-Pugh C: not recommended. |
| Pediatric use | Children ≥12 years: same as adult. Children 6-11 years: guaifenesin 300 mg / dextromethorphan 15 mg orally every 12 hours, not to exceed 2 doses in 24 hours. Children <6 years: not recommended. |
| Geriatric use | Start at lower end of dosing range (e.g., one tablet every 24 hours) due to age-related renal and hepatic decline; monitor for CNS effects and constipation. |
| 1st trimester | Avoid unless benefit outweighs risk; dextromethorphan associated with rare neural tube defects in animal studies; guaifenesin not well studied. |
| 2nd trimester | Use caution; dextromethorphan may be used short-term, but guaifenesin safety not established. |
| 3rd trimester | Avoid due to potential risk of neonatal respiratory depression and withdrawal from dextromethorphan near term. |
Clinical note
Comprehensive clinical and safety monograph for MUCINEX DM (MUCINEX DM).
| Placental transfer | Both guaifenesin and dextromethorphan are expected to cross the placenta; dextromethorphan has high lipid solubility and molecular weight <500 Da facilitating transfer. |
| Breastfeeding | Guaifenesin is excreted in breast milk in low amounts; dextromethorphan is also excreted but likely minimal. However, due to lack of robust safety data, avoid or use alternative if possible. Monitor infant for sedation or respiratory depression. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to any componentConcurrent use of MAOIs or within 14 daysRespiratory depression (severe)Asthma exacerbation (vexing cough)Phenylketonuria (contains phenylalanine in some formulations)
| Precautions | Do not use for persistent/chronic cough, cough with excessive phlegm, or cough due to smoking/asthma/COPD/emphysema, Serotonin syndrome risk with MAOIs or other serotonergic drugs, Dextromethorphan abuse potential, Hypersensitivity reactions |
| Food/Dietary | No significant food-drug interactions. However, alcohol may potentiate CNS effects (drowsiness/dizziness) and should be avoided. |
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| Lactation Rating | L3 (Moderately Safe) or Avoid |
| Teratogenic Risk | FDA Category C for guaifenesin and dextromethorphan. First trimester: limited human data; animal studies show no evidence of teratogenicity at clinically relevant doses. Second and third trimesters: no known fetal risks at recommended doses. Avoid high doses of dextromethorphan due to potential serotonin reuptake inhibition and theoretical risk of fetal serotonin syndrome. |
| Fetal Monitoring | No specific monitoring required for short-term use at recommended doses. In cases of overdose or prolonged use, monitor maternal respiratory status, CNS depression, and fetal heart rate via non-stress test if advanced gestational age. |
| Fertility Effects | No known effects on human fertility for guaifenesin or dextromethorphan at therapeutic doses. Animal studies have not shown impaired fertility. |
| Clinical Pearls |
| Mucinex DM combines guaifenesin (expectorant) and dextromethorphan (antitussive). Guaifenesin is best taken with adequate fluid intake to thin mucus. Dextromethorphan is contraindicated with MAOIs and in patients with serotonin syndrome risk. Avoid use in patients with chronic cough due to smoking, asthma, or COPD without physician guidance. |
| Patient Advice | Take with a full glass of water to help loosen phlegm. · Do not crush or chew extended-release tablets; swallow whole. · Avoid driving or operating machinery if drowsy or dizzy. · Do not use with other cough/cold medications containing dextromethorphan. · Stop use and consult doctor if cough persists >7 days or with fever, rash, or headache. |