What are the guidelines for using promethazine (Phenergan) cough syrup as a treatment for cough?

Promethazine Cough Syrup: Not Recommended for Cough Treatment

Promethazine is not recommended as a treatment for cough in children or adults, as it lacks evidence of efficacy as an antitussive and carries significant safety risks, particularly in children under 2 years of age where it is contraindicated. 1

FDA-Approved Indications and Contraindications

Promethazine is FDA-approved for allergies, motion sickness, nausea/vomiting, and sedation—but notably not for cough suppression. 1 The FDA labeling explicitly states:

• Contraindicated in children under 2 years of age due to risk of fatal respiratory depression 1
• No dosing recommendations exist for cough treatment specifically 1
• When used for approved indications in children, doses should be adjusted to the smallest amount adequate to relieve symptoms 1

Safety Concerns

Promethazine carries substantial risks that outweigh any theoretical benefit for cough:

• Significant sedation, agitation, hallucinations, seizures, and dystonic reactions have been reported 2
• Possible association with apparent life-threatening events or sudden infant death syndrome 2
• The syrup formulation increases risk of inappropriate use in young children who are most vulnerable to adverse effects 2
• Over-the-counter availability (where permitted) falsely implies safety, leading to misuse in inappropriate age groups 2

Evidence-Based Alternatives for Cough Management

For Acute Dry Cough in Adults:

First-line approach:

• Simple home remedies like honey and lemon are recommended as initial treatment—they are cheap, safe, and often as effective as pharmacological options 3, 4

If pharmacological treatment needed:

• Dextromethorphan is the preferred antitussive due to superior safety profile compared to opioid alternatives 3, 4
• Effective dose: 10-15 mg three to four times daily, with maximum suppression at 60 mg 5, 4
• Non-sedating opiate that centrally suppresses cough reflex 3, 4

For nighttime cough:

• First-generation antihistamines with sedative properties (not promethazine specifically) may be useful for nocturnal cough due to sedative effects 3, 4

Avoid:

• Codeine and pholcodine have no greater efficacy than dextromethorphan but carry significantly worse side effect profiles 3, 4

For Chronic Unexplained Cough in Adults:

If cough persists beyond 8 weeks without clear etiology:

• Gabapentin can be considered after discussing risks/benefits, with reassessment at 6 months 5
• Proton pump inhibitors should NOT be prescribed if workup for acid reflux is negative 5
• Speech pathology interventions should be considered 5

For Cough in Children:

• No evidence supports codeine or derivatives for chronic cough in children 6
• Over-the-counter cough medicines lack efficacy and can cause complications or death 7
• International guidelines and regulatory authorities (USA, Europe, Canada, New Zealand, Australia) recommend against codeine-based medications in children under 12 years 6
• Antitussives showed no benefit over placebo in pediatric studies 8
• Aetiological-based management (treating the underlying cause) is advocated rather than symptomatic suppression 6

Clinical Algorithm for Cough Management

Step 1: Assess for red flags requiring immediate evaluation:

• Hemoptysis, foreign body aspiration, increasing breathlessness (possible asthma/anaphylaxis), fever with purulent sputum 3

Step 2: For acute viral cough (duration <3 weeks):

• Recommend honey and lemon mixtures 3, 4
• If inadequate, trial dextromethorphan 10-15 mg three to four times daily 3, 4

Step 3: For persistent cough (>3 weeks):

• Evaluate for underlying causes: asthma, GERD, post-nasal drip 3
• Treat underlying condition rather than suppressing cough symptomatically 6

Step 4: For chronic unexplained cough (>8 weeks) after negative workup:

• Consider gabapentin trial with close monitoring 5
• Refer to speech pathology for cough suppression techniques 5

Key Pitfalls to Avoid

• Do not use promethazine for cough treatment—it is not indicated and carries unnecessary risks 1, 2
• Never use any cough suppressant in children under 2 years 1, 7
• Avoid codeine-based products in children under 12 years due to respiratory suppression risk and lack of efficacy 6
• Do not prescribe proton pump inhibitors empirically for chronic cough without evidence of reflux disease 5
• Recognize that most acute viral cough is self-limiting (1-3 weeks) and does not require prescription medication 3