Usage
Dextromethorphan Hydrobromide + Guaifenesin is prescribed to relieve coughs caused by the common cold, bronchitis, and other respiratory illnesses. It is also used to treat chest congestion.
Pharmacological Classification:
- Dextromethorphan: Antitussive (Cough suppressant)
- Guaifenesin: Expectorant
Mechanism of Action:
- Dextromethorphan acts on the cough center in the brain to suppress the urge to cough.
- Guaifenesin thins and loosens mucus in the airways, making it easier to cough up and clearing congestion.
Alternate Names
This combination medication is often referred to as Dextromethorphan/Guaifenesin.
Brand Names:
Robitussin DM, Mucinex DM, Delsym Cough Plus Chest Congestion DM, and various generic versions.
How It Works
Pharmacodynamics:
Dextromethorphan suppresses the cough reflex by acting as an NMDA receptor antagonist in the central nervous system. Guaifenesin increases respiratory tract fluid secretions, making the mucus less viscous and easier to expectorate.
Pharmacokinetics:
- Absorption: Both drugs are readily absorbed from the gastrointestinal tract.
- Metabolism: Dextromethorphan is extensively metabolized in the liver, primarily by CYP2D6 and CYP3A4 enzymes. Guaifenesin is also metabolized in the liver.
- Elimination: Metabolites of both drugs are primarily excreted in the urine.
Mode of Action:
Dextromethorphan’s antitussive effect is mediated by its action on sigma-1 receptors and its nonselective inhibition of serotonin reuptake. Guaifenesin’s expectorant action is thought to involve stimulation of gastric vagal receptors.
Receptor Binding, Enzyme Inhibition, or Neurotransmitter Modulation:
Dextromethorphan acts as an NMDA receptor antagonist, sigma-1 receptor agonist, and serotonin reuptake inhibitor.
Elimination Pathways:
Both drugs are primarily eliminated via hepatic metabolism and renal excretion.
Dosage
Standard Dosage
Adults:
- Liquid: 10-20 mg dextromethorphan/100-200 mg guaifenesin every 4 hours, not to exceed 120 mg dextromethorphan/2.4 g guaifenesin in 24 hours.
- Extended-Release Tablets: 60 mg dextromethorphan/1200 mg guaifenesin every 12 hours, not to exceed 120 mg dextromethorphan/2400 mg guaifenesin in 24 hours.
Children:
Use in children under 4 years old is generally not recommended. Consult a healthcare professional for dosing in children 4-12 years old, as dosage varies by age and formulation. Do not use extended-release formulations in children under 12 years old.
Special Cases:
- Elderly Patients: No specific dosage adjustments are typically needed.
- Patients with Renal Impairment: No specific dosage adjustments are typically needed.
- Patients with Hepatic Dysfunction: Use with caution due to hepatic metabolism.
- Patients with Comorbid Conditions: Consider drug interactions and individual patient factors.
Clinical Use Cases
This medication is not typically used in clinical settings like intubation, surgical procedures, mechanical ventilation, or the ICU. It is primarily used for symptomatic relief of cough and chest congestion in outpatient settings.
Dosage Adjustments
Adjustments may be needed based on patient response and tolerance. Always refer to specific product labeling for detailed instructions.
Side Effects
Common Side Effects
Dizziness, drowsiness, nausea, vomiting, diarrhea, headache, rash, and itching.
Rare but Serious Side Effects
Allergic reactions (hives, difficulty breathing, swelling), mood changes, severe headache, severe dizziness, anxiety, or feeling like passing out.
Long-Term Effects
No specific long-term effects have been identified, but prolonged use should be avoided unless medically necessary.
Adverse Drug Reactions (ADR)
Serotonin syndrome (when combined with other serotonergic drugs), respiratory depression (with excessive doses).
Contraindications
- Hypersensitivity to dextromethorphan or guaifenesin.
- Concurrent or recent (within 14 days) use of monoamine oxidase inhibitors (MAOIs).
Drug Interactions
- MAOIs: Increased risk of serotonin syndrome.
- CNS depressants (alcohol, opioids, benzodiazepines): Additive sedative effects.
- Serotonergic drugs (SSRIs, SNRIs, TCAs): Increased risk of serotonin syndrome.
- CYP2D6 and CYP3A4 inhibitors or inducers: May alter dextromethorphan metabolism.
Pregnancy and Breastfeeding
Limited data are available on pregnancy outcomes. Consult a physician to assess the benefit versus risk. Dextromethorphan is likely present in breast milk, although at low levels. Avoid alcohol-containing formulations during pregnancy and breastfeeding.
Drug Profile Summary
- Mechanism of Action: Dextromethorphan: Centrally acting antitussive; Guaifenesin: Expectorant.
- Side Effects: Dizziness, drowsiness, nausea, vomiting.
- Contraindications: Hypersensitivity, concurrent MAOI use.
- Drug Interactions: MAOIs, CNS depressants, serotonergic drugs.
- Pregnancy & Breastfeeding: Consult a physician.
- Dosage: See detailed dosage guidelines above.
- Monitoring Parameters: Respiratory status, cough frequency and severity.
Popular Combinations
Often combined with other cough and cold medications, including antihistamines, decongestants, and analgesics.
Precautions
- General Precautions: Assess for allergies and potential drug interactions.
- Specific Populations: Consult a physician regarding use during pregnancy and breastfeeding. Use with caution in patients with hepatic dysfunction. Not generally recommended for children under 4.
- Lifestyle Considerations: Avoid alcohol and other CNS depressants. May impair alertness; caution with driving or operating machinery.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Dextromethorphan Hydrobromide + Guaifenesin?
A: Please refer to the detailed dosage section above, as it varies based on age, formulation, and individual patient factors.
Q2: Can this medication be used in children?
A: Use in children under 4 years old is generally not recommended. Consult a healthcare professional for pediatric dosing.
Q3: Is it safe to take this medicine while pregnant or breastfeeding?
A: Limited data are available. Consult a physician to evaluate the benefits and risks.
Q4: What are the common side effects?
A: Common side effects include dizziness, drowsiness, nausea, and vomiting.
Q5: Can I take this with other cough and cold medicines?
A: Consult a physician or pharmacist before combining with other medications, as interactions may occur.
Q6: Are there any contraindications?
A: Do not use if you are currently taking or have recently taken MAOIs.
Q7: What should I do if I miss a dose?
A: Take the missed dose as soon as possible, unless it’s almost time for the next dose. Do not double the dose.
Q8: How long should I take this medicine?
A: Use only for short-term relief of symptoms. Consult a physician if symptoms persist beyond 7 days.
Q9: Can I operate machinery or drive after taking this medication?
A: Use caution as the medication may cause drowsiness or dizziness. Avoid operating machinery or driving if impaired.
Q10: What is the difference between an expectorant and a cough suppressant?
A: An expectorant (guaifenesin) thins mucus, while a cough suppressant (dextromethorphan) reduces the urge to cough.
