What is the dosage and usage of Dextromethorphan (cough suppressant) polistirex for temporary relief of coughs?

Dextromethorphan Polistirex Dosing and Usage

Direct Recommendation

For temporary relief of cough due to minor throat and bronchial irritation, dextromethorphan polistirex is dosed as 30 mg (equivalent to dextromethorphan hydrobromide) every 12 hours in adults, with maximum cough suppression achieved at 60 mg doses, though this extended-release formulation should be used cautiously as it has 2-3 times longer duration than standard formulations. 1, 2, 3

FDA-Approved Indications

• Dextromethorphan polistirex temporarily relieves cough due to minor throat and bronchial irritation as may occur with the common cold or inhaled irritants 1
• It also suppresses the impulse to cough to help patients get to sleep 1

Dosing Specifications

Standard Adult Dosing

• Each 5 mL of dextromethorphan polistirex contains the equivalent of 30 mg dextromethorphan hydrobromide 1
• The polistirex formulation is extended-release with a duration of action approximately 2-3 times longer than standard dextromethorphan hydrobromide 3

Optimal Therapeutic Dosing

• Maximum cough reflex suppression occurs at 60 mg of dextromethorphan, demonstrating a clear dose-response relationship 2, 4
• The British Thoracic Society recommends dextromethorphan as the preferred pharmacological option due to superior efficacy and better safety profile compared to codeine and other opioid antitussives 2, 5

Clinical Context and Appropriate Use

When to Use Dextromethorphan Polistirex

• Chronic bronchitis: Central cough suppressants including dextromethorphan are recommended for short-term symptomatic relief (Level of evidence: fair; benefit: intermediate; grade B) 6
• Nocturnal cough: Particularly useful for suppressing the impulse to cough to facilitate sleep 1

When NOT to Use

• Upper respiratory infections (URI): Central cough suppressants including dextromethorphan have limited efficacy for cough due to URI and are not recommended (Level of evidence: good; benefit: none; grade D) 6, 2
• Suspected pneumonia: Do not use in patients with tachycardia, tachypnea, fever, or abnormal chest examination findings until pneumonia is ruled out 2
• Acute viral cough in children: Dextromethorphan does not relieve cough better than placebo in pediatric patients 7

Important Safety Considerations

Formulation Warnings

• Verify combination ingredients: Some dextromethorphan preparations contain additional ingredients like paracetamol (acetaminophen), which can lead to unintentional overdosing 2, 5
• Extended duration: The polistirex formulation has unchanged pharmacokinetics once liberated but releases active ingredient slowly, resulting in prolonged clinical effects 3

Toxicity Risk

• Pediatric overdose at 71.4 mg/kg resulted in life-threatening toxicity requiring intubation, with blood concentration of 110 ng/mL (therapeutic range 10-40 ng/mL) 3
• Toxic effects included unresponsiveness, tachycardia, hypertension, mydriasis, roving eye movements, rotary nystagmus, and opisthotonos 3

Preferred Treatment Algorithm

Step 1: First-Line Non-Pharmacological

• Start with simple home remedies like honey and lemon, which are the simplest, cheapest, and often as effective as pharmacological treatments 2, 4

Step 2: Pharmacological Treatment Selection

• For chronic bronchitis with bothersome cough: Dextromethorphan polistirex 30 mg every 12 hours, may increase to 60 mg for maximum effect 2, 1
• For nocturnal cough disrupting sleep: Consider dextromethorphan polistirex due to extended-release properties, or alternatively first-generation antihistamines with sedative properties 2, 1

Step 3: Alternative Options if Dextromethorphan Ineffective

• Ipratropium bromide: The only inhaled anticholinergic recommended for cough suppression in URI or chronic bronchitis 6, 5
• First-generation antihistamines: Particularly useful for nocturnal cough due to sedative effects 2, 4

Critical Pitfalls to Avoid

• Do not prescribe for acute URI: Despite widespread use, evidence shows no benefit over placebo for acute upper respiratory tract infections 6, 2
• Avoid codeine: Codeine and pholcodine have no greater efficacy than dextromethorphan but carry significant adverse side effect profiles 2, 4, 5
• Do not use subtherapeutic doses: Doses below 60 mg may be inadequate for severe cough given the dose-response relationship 2, 5
• Check for contraindicated combinations: Verify the formulation does not contain ingredients to which the patient has allergies 5