Adult: As dextromethorphan hydrobromide immediate-release preparation: As liquid-filled cap, caplet, or oral solution: 10-20 mg 4-6 hourly, or 30 mg 6-8 hourly as necessary. Max: 80-120 mg daily. As syr: 20 mg 4 hourly as needed. Max: 120 mg daily. As loz: Suck 1 loz (2.5 mg) as needed. Max: 10 loz daily. As dextromethorphan polistirex extended-release susp (expressed as dextromethorphan hydrobromide equivalent): 60 mg 12 hourly. Dosage recommendations may vary among countries or individual products. Refer to specific product guidelines. Child: As dextromethorphan hydrobromide immediate-release preparation: As oral solution: 6-<12 years 15 mg 6-8 hourly. As liquid-filled cap, caplet, oral solution: ≥12 years Same as adult dose. As syr: 2-<6 years 5 mg 4 hourly as needed. Max: 30 mg daily; 6-<12 years 10 mg 4 hourly as needed. Max: 60 mg daily; ≥12 years Same as adult dose. As loz: 6-12 years Suck 1 loz (2.5 mg) as needed. Max: ≤2 loz within 4 hours or ≤7 loz daily. Max duration: 5 days; >12 years Same as adult dose. As dextromethorphan polistirex extended-release susp (expressed as dextromethorphan hydrobromide equivalent): 4-<6 years 15 mg 12 hourly; 6-<12 years 30 mg 12 hourly; ≥12 years Same as adult dose. Dosage recommendations may vary among countries or individual products. Refer to specific product guidelines.
Special Patient Group
Pharmacogenomics:
Dextromethorphan is primarily metabolised by the CYP2D6 enzyme.
Approx 10% of the general population are poor metabolisers of CYP2D6. Individuals who are poor metabolisers of CYP2D6 may experience exaggerated and/or prolonged effects of dextromethorphan. Currently, there are no dosing recommendations for the use of dextromethorphan in this population, however, caution should be exercised.
Hepatic Impairment
Contraindicated.
Administration
May be taken with or without food.
Incompatibility
Incompatible with penicillins, tetracyclines, salicylates, phenobarbital Na, hydroiodic acid, and high concentrations of Na or K iodide.
Contraindications
Acute asthma attack, respiratory insufficiency or respiratory depression; chronic cough that lasts as occurs with smoking, emphysema, or cough that occurs with too much phlegm (mucus). Individuals at risk of developing respiratory failure (e.g. COPD, pneumonia). Hepatic impairment. Concomitant use with MAOIs (and within 14 days of stopping treatment), SSRIs, other antidepressants (e.g. TCAs), or medicines for Parkinson's disease.
Special Precautions
Patient with history of asthma, current or history of substance misuse disorder (including alcohol abuse) or mental health disorder (e.g. major depression). CYP2D6 poor metabolisers. Debilitated patients. Children (especially atopic children). Treatment with a cough medicine in children (particularly under 12 years of age) should be considered carefully due to potential risks and limited evidence on efficacy. Pregnancy and lactation.
Adverse Reactions
Significant: Drug dependence (particularly with prolonged use). Gastrointestinal disorders: Diarrhoea, gastrointestinal distress, stomach pain, nausea, vomiting. Nervous system disorders: Dizziness, drowsiness, convulsions. Psychiatric disorders: Excitation, mental confusion, nervousness, restlessness. Respiratory, thoracic and mediastinal disorders: Respiratory depression. Skin and subcutaneous tissue disorders: Rash.
This drug may cause dizziness or drowsiness, if affected, do not drive or operate machinery.
Overdosage
Symptoms: Nausea, vomiting, dystonia, agitation, confusion, somnolence, stupor, nystagmus, cardiotoxicity (e.g. tachycardia, abnormal ECG including QTc prolongation), ataxia, toxic psychosis with visual hallucinations, hyperexcitability, CNS depression, dizziness, dysarthria, abdominal discomfort and hypotension. Coma, respiratory depression, or convulsions may occur in the event of a massive overdose. Management: Symptomatic and supportive treatment. Activated charcoal may be given to asymptomatic patients within 1 hour of ingestion. Administration of naloxone may be considered in sedated or comatose patients. Benzodiazepines may be given for seizures. External cooling with benzodiazepines may be used to manage hyperthermia from serotonin syndrome. Gastric lavage may also be considered.
Drug Interactions
Concomitant use with CYP2D6 inhibitors (e.g. quinidine, amiodarone, haloperidol, thioridazine) may increase the serum levels of dextromethorphan. May increase the effect of CNS depressants (e.g. narcotic analgesics, antihistamines). Potentially Fatal: Serotonin syndrome may occur with concomitant use of MAOIs (and within 14 days of stopping MAOI treatment), SSRIs (e.g. fluoxetine), TCAs (e.g. clomipramine, imipramine) or medicines for Parkinson's disease.
Food Interaction
May increase the CNS depressant effect of alcohol.
Lab Interference
May cause false-positive results in phencyclidine, opioids, and heroin urine drug screening.
Action
Description: Mechanism of Action: Dextromethorphan, a centrally-acting antitussive agent, depresses the cough centre in the medulla oblongata through sigma receptor stimulation, resulting in decreased sensitivity of cough receptors and interruption of cough impulse transmission. Onset: 15-30 minutes. Duration: Approx 3-6 hours (immediate-release preparation). Pharmacokinetics: Absorption: Rapidly and well absorbed from the gastrointestinal tract. Time to peak plasma concentration: 2.1-2.6 hours. Distribution: Widely distributed; actively taken up and concentrated in the brain tissue. Metabolism: Metabolised in the liver via demethylation by CYP2D6 to dextrorphan (active metabolite); CYP3A4 and CYP3A5 form smaller amounts of 3-hydroxy and 3-methoxy derivatives. It undergoes rapid and extensive first-pass metabolism. Excretion: Mainly via urine, as unchanged drug and demethylated metabolites. Elimination half-life: 1.2-3.9 hours (dextromethorphan); 3.4-5.6 hours (dextrorphan).
Chemical Structure
Dextromethorphan Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 5360696, Dextromethorphan. https://pubchem.ncbi.nlm.nih.gov/compound/Dextromethorphan. Accessed June 27, 2022.
R05DA09 - dextromethorphan ; Belongs to the class of opium alkaloids and derivatives. Used as cough suppressant.
References
Tateishi T, Chida M, Ariyoshi N et al. Analysis of the CYP2D6 Gene in Relation to Dextromethorphan O-demethylation Capacity in a Japanese Population. Clin Pharmacol Ther. 1999;65(5):570-5. doi: 10.1016/S0009-9236(99)70077-9. Accessed 31/03/2022. PMID: 10340923Annotation of CYP2D6*1, CYP2D6*10. Pharmacogenomics Knowledgebase (PharmGKB). https://www.pharmgkb.org. Accessed 31/03/2022.Annotation of CYP2D6*1, CYP2D6*5. Pharmacogenomics Knowledgebase (PharmGKB). https://www.pharmgkb.org. Accessed 31/03/2022.Anon. Dextromethorphan. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 25/03/2022.Anon. Dextromethorphan. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 25/03/2022.Benylin Dry Cough 7.5 mg/5 mL Syrup (McNeil Products Limited). MHRA. https://products.mhra.gov.uk. Accessed 25/03/2022.Boots Dry Cough Relief 2.5 mg Lozenges (The Boots Company PLC). MHRA. https://products.mhra.gov.uk. Accessed 25/03/2022.Buckingham R (ed). Dextromethorphan. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 25/03/2022.Delsym Cough Tablet (RB Health US LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 25/03/2022.Delsym Suspension, Extended Release (RB Health US LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 25/03/2022.Dextromethorphan HBr Capsule, Liquid Filled (Rugby Laboratories). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 25/03/2022.Dextrophan Syrup (Upha Pharmaceutical Mfg. Sdn. Bhd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 25/03/2022.Lemocalm Dry Cough 10 mg/5 mL Oral Solution (Bristol Laboratories Limited). MHRA. https://products.mhra.gov.uk. Accessed 25/03/2022.Pfizer New Zealand Limited. Robitussin Dry Cough Forte data sheet 21 May 2020. Medsafe. http://www.medsafe.govt.nz. Accessed 25/03/2022.Tussidex Forte Linctus (Xepa-Soul Pattinson Malaysia Sdn Bhd). MIMS Hong Kong. http://www.mims.com/hongkong. Accessed 25/03/2022.
Sign Out
