What is the appropriate dose and safety considerations for codeine‑containing cough syrup in a healthy adult who is not pregnant, has no severe chronic lung disease, no opioid allergy, no substance‑use disorder, and no recent head or spinal injury?

Codeine Cough Syrup: Dosing and Safety

Codeine should not be your first-line choice for cough suppression in a healthy adult—dextromethorphan 60 mg is equally effective with a far superior safety profile and should be used instead. 1, 2

Why Codeine Is Not Recommended First-Line

• Codeine has no greater efficacy than dextromethorphan but carries a significantly worse adverse effect profile, including drowsiness, nausea, constipation, respiratory depression, and risk of physical dependence. 1, 2
• Multiple guideline bodies explicitly recommend dextromethorphan over codeine due to superior safety with equivalent efficacy. 2
• If an opioid antitussive is truly necessary after non-opioid options fail, pholcodine, hydrocodone, or dihydrocodeine are preferred over codeine due to better side effect profiles. 1

If Codeine Must Be Used: Dosing and Administration

FDA-approved dosing for adults is 10 mL (containing codeine) every 4 hours, not to exceed 6 doses in 24 hours. 3

• For refractory cough in specific contexts (lung cancer, palliative care), the American College of Chest Physicians recommends codeine 30-60 mg four times daily. 1
• A bedtime dose may be used specifically to suppress nocturnal cough and induce undisturbed sleep in palliative settings. 1

Critical Safety Considerations and Contraindications

• Codeine is absolutely contraindicated in productive cough with significant sputum, where cough serves a necessary physiological clearance function—suppressing this can worsen outcomes. 1
• Screen for substance use disorders before prescribing, as codeine carries addiction risk and dependence potential. 1
• Avoid concomitant use with benzodiazepines or other CNS depressants, which significantly increases overdose risk. 1
• Monitor for respiratory depression, particularly in opioid-naive patients or those with any degree of respiratory compromise. 4
• Codeine is a prodrug requiring CYP2D6 metabolism to morphine for effect—genetic variability means some patients are ultra-rapid metabolizers (increased toxicity risk) while others are poor metabolizers (no therapeutic effect). 5

Recommended Treatment Algorithm Instead

Start with non-pharmacological measures:

• Honey and lemon is the simplest, cheapest initial approach for acute viral cough. 1, 2

If pharmacological treatment is needed:

• Use dextromethorphan 60 mg for maximum cough reflex suppression (not the subtherapeutic 10-15 mg doses in most OTC preparations). 1, 2
• For nocturnal cough specifically, add a sedating first-generation antihistamine like chlorpheniramine. 1, 2
• Menthol inhalation provides acute short-term relief when needed. 1, 2

If non-opioid options fail:

• Consider hydrocodone 5 mg twice daily (titrate to 10 mg/day), which demonstrates 70% reduction in cough frequency and is preferred over codeine. 1
• Dihydrocodeine 10 mg three times daily is another alternative with better tolerability than codeine. 1

Reserve morphine only for refractory cough unresponsive to all other measures, starting at 5 mg trial dose, then 5-10 mg slow-release twice daily if effective. 6

Duration of Therapy

• If short-course treatment (3-5 days) does not produce improvement, discontinue and try alternative approaches rather than continuing ineffective therapy. 1
• Limit codeine use only when and as long as clinically necessary—prolonged use increases dependence risk. 5

Common Pitfalls to Avoid

• Do not use subtherapeutic OTC dextromethorphan doses—the effective dose is 60 mg, not the typical 10-15 mg in most preparations. 1, 2
• Do not suppress productive cough—this worsens outcomes by preventing necessary airway clearance. 1
• Do not continue ineffective therapy beyond 3-5 days—reassess and change approach. 1
• Do not overlook polypharmacy risks—check for other CNS depressants or multiple cough/cold products. 1