Usage
- Dextromethorphan Hydrobromide is prescribed for the temporary relief of non-productive cough caused by minor throat and bronchial irritation, such as that which may occur with the common cold or inhaled irritants. It is also used to suppress the impulse to cough to help induce sleep.
- Pharmacological Classification: Antitussive (Cough Suppressant)
- Mechanism of Action: Dextromethorphan acts centrally on the cough center in the medulla oblongata by increasing the cough threshold. It does not exhibit analgesic, sedative, or respiratory depressant effects at usual antitussive doses.
Alternate Names
- Dextromethorphan HBr
- DXM (abbreviation)
- Robitussin DM (brand name, combined with guaifenesin)
- Delsym (brand name)
How It Works
- Pharmacodynamics: Dextromethorphan suppresses the cough reflex by acting on the cough center in the medulla. At higher doses, it acts as an NMDA receptor antagonist, producing dissociative effects.
- Pharmacokinetics:
- Absorption: Well-absorbed from the gastrointestinal tract.
- Metabolism: Extensively metabolized in the liver, primarily by CYP2D6 with polymorphic metabolism (poor metabolizers may experience prolonged effects). Dextrorphan, a metabolite, also has antitussive activity.
- Elimination: Excreted in the urine as unchanged drug and metabolites. Half-life varies (1.2 to 3.9 hours in extensive metabolizers, up to 45 hours in poor metabolizers).
- Mode of Action: Binds to and antagonizes NMDA receptors in the central nervous system, particularly in the cough center, at higher doses. At lower doses, the mechanism is not fully understood but appears to involve sigma-1 receptor agonism and effects on serotonin and norepinephrine reuptake.
- Receptor Binding/Enzyme Inhibition/Neurotransmitter Modulation:
- NMDA receptor antagonist (at higher doses)
- Sigma-1 receptor agonist (at lower doses)
- Possible effects on serotonin and norepinephrine reuptake
- Elimination Pathways: Primarily renal excretion of metabolites.
Dosage
Standard Dosage
Adults:
- Immediate-release: 10-20 mg orally every 4 hours, or 30 mg every 6-8 hours, as needed. Maximum: 120 mg/day.
- Extended-release: 60 mg orally every 12 hours. Maximum: 120 mg/day.
Children:
- Immediate-release:
- 2-6 years: 2.5-5 mg orally every 4 hours or 7.5 mg every 6-8 hours, as needed. Maximum: 30 mg/day.
- 6-12 years: 5-10 mg orally every 4 hours, or 15 mg every 6-8 hours, as needed. Maximum: 60 mg/day.
- 12 years and older: Same as adult dose.
- Extended-release:
- 4-6 years: 15 mg orally every 12 hours. Maximum: 30 mg/day.
- 6-12 years: 30 mg orally every 12 hours. Maximum: 60 mg/day.
- 12 years and older: Same as adult dose.
- Lozenges:
- 6-12 years: 5-10 mg every 1-4 hours as needed, not to exceed 60 mg/day.
- 12 years and older: 5-15 mg every 1-4 hours as needed, not to exceed 120 mg/day.
Special Cases:
- Elderly Patients: No specific dosage adjustments are needed for elderly patients. But it’s necessary to consider age-related decline in kidney or liver function and administer the lowest effective dose.
- Patients with Renal Impairment: Caution is advised in patients with moderate to severe renal impairment. Dosage adjustments may be necessary.
- Patients with Hepatic Dysfunction: Contraindicated in patients with hepatic impairment.
- Patients with Comorbid Conditions: Use with caution in patients with asthma, chronic obstructive pulmonary disease (COPD), or pneumonia. Avoid in patients with respiratory failure.
Clinical Use Cases
Dextromethorphan is typically used for outpatient management of cough and is not indicated for use in clinical settings like intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations.
Dosage Adjustments
Consider dosage modifications in patients with renal impairment, metabolic disorders, or genetic polymorphisms affecting drug metabolism, particularly CYP2D6 poor metabolizers. Consult clinical guidelines and expert recommendations for appropriate adjustments.
Side Effects
Common Side Effects
- Dizziness
- Drowsiness
- Nausea
- Vomiting
- Stomach Discomfort
- Constipation
Rare but Serious Side Effects
- Allergic reactions (hives, difficulty breathing, swelling)
- Seizures
- Confusion
- Hallucinations
- Slow, shallow breathing
- Serotonin Syndrome (with concomitant use of serotonergic drugs): agitation, confusion, hallucinations, fever, sweating, shivering, fast heart rate, muscle stiffness, twitching, loss of coordination, nausea, vomiting, diarrhea
Long-Term Effects
- Drug dependence (with prolonged high-dose misuse).
Adverse Drug Reactions (ADR)
- Serotonin syndrome
- Respiratory depression (overdose)
Contraindications
- Hypersensitivity to dextromethorphan
- Concurrent use of MAOIs (or within 14 days of discontinuing MAOIs)
- Respiratory insufficiency or depression
- Acute asthma attack
- Chronic cough associated with excessive secretions
- Patients with or at risk of respiratory failure (e.g., COPD, pneumonia)
- Hepatic impairment
Drug Interactions
- MAOIs: Concomitant use is contraindicated due to the risk of serotonin syndrome and other severe reactions.
- SSRIs, SNRIs, TCAs: Increased risk of serotonin syndrome.
- CYP2D6 Inhibitors: (e.g., quinidine, amiodarone, fluoxetine, paroxetine) Increased serum levels of dextromethorphan and risk of adverse effects.
- CNS Depressants: (e.g., alcohol, opioids, benzodiazepines) Additive CNS depression.
- Alcohol: May potentiate the sedative effects.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: C. Use only if the potential benefit justifies the potential risk to the fetus. Avoid alcohol-containing formulations.
- Breastfeeding: Limited data available. Use caution; consider the potential for infant exposure. Alcohol-containing formulations should be avoided. Safer alternatives may be preferred.
Drug Profile Summary
- Mechanism of Action: Centrally acting antitussive, NMDA receptor antagonist (higher doses).
- Side Effects: Dizziness, drowsiness, nausea, vomiting, serotonin syndrome (with serotonergic drugs).
- Contraindications: Hypersensitivity, concurrent MAOI use, respiratory failure, hepatic impairment.
- Drug Interactions: MAOIs, SSRIs/SNRIs, CYP2D6 inhibitors, CNS depressants.
- Pregnancy & Breastfeeding: Category C; use with caution.
- Dosage: See detailed dosage guidelines above.
- Monitoring Parameters: Respiratory status, especially in patients with underlying respiratory conditions.
Popular Combinations
- Dextromethorphan + Guaifenesin: For relief of cough with mucus.
Precautions
- General Precautions: Assess for allergies, pre-existing respiratory conditions, concurrent medications.
- Specific Populations: See dosage adjustments section.
- Lifestyle Considerations: Avoid alcohol. Caution when driving or operating machinery.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Dextromethorphan Hydrobromide?
A: See detailed dosage guidelines above.
Q2: How does dextromethorphan work to suppress cough?
A: Dextromethorphan primarily acts on the cough center in the medulla oblongata to raise the threshold for coughing.
Q3: What are the common side effects?
A: Common side effects include dizziness, drowsiness, nausea, and vomiting.
Q4: Is dextromethorphan safe to use during pregnancy?
A: Dextromethorphan is a Pregnancy Category C medication. Use only if clearly needed and the potential benefit outweighs the potential risk to the fetus.
Q5: Can dextromethorphan be used with other cough and cold medications?
A: Generally, it is not recommended to combine dextromethorphan with other cough and cold medications, especially those containing CNS depressants or other antitussives, without consulting a healthcare professional.
Q6: What are the serious side effects to watch out for?
A: Serious side effects may include allergic reactions, seizures, confusion, hallucinations, and slowed breathing. Serotonin syndrome can occur with concomitant use of serotonergic drugs.
Q7: Can patients with liver problems take dextromethorphan?
A: Dextromethorphan is contraindicated in patients with hepatic impairment.
Q8: What should patients be advised regarding lifestyle while taking this medication?
A: Patients should avoid alcohol while taking dextromethorphan. They should also exercise caution when driving or operating machinery due to the potential for drowsiness and dizziness.
Q9: What is the maximum daily dose of dextromethorphan?
A: The maximum daily dose for adults is generally 120 mg, regardless of the formulation (immediate-release or extended-release). Lower maximum doses apply for children, depending on their age.
Q10: Can dextromethorphan be used in patients with asthma or COPD?
A: Dextromethorphan should be used with caution in patients with asthma or COPD, and it is contraindicated in patients with respiratory failure or during an acute asthma attack. It should not be used to suppress a chronic, productive cough.
