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Dextromethorphan

 

1. Generic Name & Brand Names

  • Generic Name: Dextromethorphan HBr

  • Common Brands:

    • Robitussin® DM

    • Delsym® (extended-release)

    • Vicks® DayQuil Cough

    • Theraflu® Cough Relief

    • Generic/store brands ("Tussin", "Cough Suppressant")

2. Dosage Forms

  • Oral:

    • Syrup (3-15 mg/5mL)

    • Extended-release suspension (30 mg/5mL)

    • Gel capsules (15-30 mg)

    • Lozenges/sprays

  • Combination Products:

    • With guaifenesin (Mucinex DM®)

    • With antihistamines (NyQuil®)

3. Drug Class

  • NMDA Receptor Antagonist

  • Sigma-1 receptor agonist

  • Centrally-acting antitussive (cough suppressant)

  • Not an analgesic or expectorant

4. Uses

  • Symptomatic Relief of Non-Productive Cough:

    • Common cold, bronchitis, throat irritation

  • Off-label/Investigational:

    • Treatment-resistant depression (with bupropion: Auvelity®)

    • Neuropathic pain

    • Pseudobulbar affect

5. Side Effects

Common (≥5%)Serious (Discontinue Immediately)
DrowsinessSerotonin Syndrome
DizzinessRespiratory Depression (high doses)
NauseaBradycardia
At High Doses:Dissociative Hallucinations
• ConfusionSeizures
• AtaxiaAcute Liver Injury (APAP combos)

6. Critical Warnings

  • 🚫 Contraindications:

    • MAOI use (risk of fatal serotonin toxicity)

    • Asthma/chronic bronchitis with productive cough

  • Black Box Warning (Combination Products):

    • Acetaminophen overdose risk in multi-symptom formulations

  • Abuse Potential:

    • "Robotripping" - recreational use causes dissociative effects at 5-10x doses

    • Schedule V controlled substance in some states

  • Drug Interactions:

    • ⚠️ SSRIs/SNRIs: Serotonin syndrome (agitation, hyperthermia)

    • ⚠️ Quinidine: ↑ DXM levels 20-fold (CYP2D6 inhibition)

7. How to Take

FormAdults (Max Daily)Children (6-12 yrs)
Immediate-Release10-30 mg q4-8h (120 mg)5-15 mg q4-8h (60 mg)
Extended-Release60 mg q12h (120 mg)30 mg q12h (60 mg)

  • Key Rules:

    • Use lowest effective dose for ≤7 days

    • Never combine with alcohol

    • Avoid in children <6 years (AAP recommendation)

8. Toxicity & Overdose

Dose RangeEffects
100-200 mgEuphoria, nystagmus
200-500 mgDissociation, hallucinations
>500 mgComa, respiratory failure

  • Management:

    • Naloxone ineffective (non-opioid mechanism)

    • Activated charcoal + benzodiazepines for seizures

9. Abuse Deterrence

  • "Robotripping" Risks:

    • Hypertension, hyperthermia, brain damage

    • Common in adolescents (easy OTC access)

  • High-Risk Formulations:

    • Alcohol-containing syrups (up to 10% ethanol)

    • Coricidin® ("Triple C") - antihistamine combo causes tachycardia

10. Storage & Safety

  • Lock Away: High abuse potential - keep in secure cabinet

  • Check Combo Products: Many contain acetaminophen (liver risk)

  • Disposal: Use drug take-back programs

Clinical Alternatives for Dry Cough

DrugAdvantageRisk Profile
HoneySafe for >1 year oldNone
PholcodineLess abuse potentialDrowsiness (EU/Asia only)
CodeinePrescription-onlyAddiction/respiratory depression

Critical Safety Alerts

⚠️ Serotonin Syndrome Risk:

  • Fatal cases reported with SSRIs (e.g., fluoxetine) - require 2-week washout.
    ⚠️ Pediatric Mortality:

  • Avoid under age 6 - no proven efficacy and high overdose risk.
    ⚠️ "DXM Calculator" Danger:

  • Online calculators promote recreational dosing - educate teens/parents.

Dextromethorphan vs. Codeine

ParameterDextromethorphanCodeine
MechanismNMDA antagonistμ-opioid agonist
Addiction RiskModerate (high dose)High
CNS DepressionLow (therapeutic dose)Significant
OTC StatusYesPrescription-only

Professional Guidance

✅ Appropriate Use:

  • Short-term suppression of non-productive cough in adults

  • Delsym® for nighttime cough (12-hour duration)
    ❌ Avoid When:

  • Productive cough (retains infection)

  • Asthma/COPD exacerbations

  • With MAOIs/SSRIs/sibutramine
    💡 Pro Tip:

For viral cough: honey (10g) > DXM for efficacy/safety in children (Pediatrics).

📊 Efficacy Note:

  • 30 mg DXM reduces cough frequency by 25-40% vs. placebo (Cochrane Review).

  • No benefit over placebo in children under 12 (BMJ).

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