Introduction
Dextromethorphan is a levorphanol derivative and codeine analog commonly used as a cough suppressant and also a drug of abuse. Although similar in structure to other opioids, it has minimal interaction with opioid receptors.
Uses
Dextromethorphan is an NMDA receptor antagonist used to treat cases of dry cough.
Dextromethorphan is indicated in combination with brompheniramine and pseudoephedrine in the treatment of coughs and upper respiratory symptoms associated with allergies or the common cold. Dextromethorphan is also used in combination with guaifenesin as an over the counter product to relieve a cough. Dextromethorpahn in combination with quinidine is indicated in the treatment of pseudobulbar affect.
Associated Conditions
Pharmacodynamics
Dextromethorphan is an opioid-like molecule indicated in combination with other medication in the treatment of coughs and pseudobulbar affect. It has a moderate therapeutic window, as intoxication can occur at higher doses. Dextromethorphan has a moderate duration of action. Patients should be counselled regarding the risk of intoxication.
Mechanism of Action
Dextromethorphan is an agonist of NMDA and sigma-1 receptors. It is also an antagonist of α3/β4 nicotinic receptors.[A10589] However, the mechanism by which dextromethorphan's receptor agonism and antagonism translates to a clinical effect is not well understood.
Absorption
A 30mg oral dose of dextromethorphan reaches a Cmax of 2.9 ng/mL, with a Tmax of 2.86 h, and an AUC of 17.8 ng*h/mL.
Volume of Distribution
The volume of distribution of dextromethorphan is 5-6.7L/kg.
Protein Binding
Dextromethorphan is 60-70% protein bound in serum.
Half Life
Dextromethorphan has a half life of 3-30 hours.
Toxicity
A dextromethorphan overdose may present as nausea, vomiting, stupor, coma, respiratory depression, seizures, tachycardia, hyperexcitability, toxic psychosis, ataxia, nystagmus, dystonia, blurred vision, changes in muscle reflexes, and serotonin syndrome. Overdose should be managed through symptomatic and supportive measures.
Food Interactions
- Take with or without food. The absorption is unaffected by food.
Dosage
Children between 6 and 12 years: 5-15 mg up to four times per day.
Children between 2 and 6 years: 2.5-5 mg up to four times per day.
