diphenhydramine hydrochloride + levomenthol: clinical use

Prescribing considerations

• Confirm the exact formulation and licensed age range.
• Assess persistent or chronic cough, asthma, excessive secretions, glaucoma risk, urinary retention, hepatic disease and moderate-to-severe renal dysfunction.
• Consider sedation, anticholinergic burden and concurrent CNS depressants.
• Review excipients where diabetes, hereditary fructose intolerance, sugar malabsorption or formulation sensitivities are relevant.

Contraindications and cautions

• Hypersensitivity to diphenhydramine, levomenthol or an excipient.
• Current MAOI treatment or use within the preceding 14 days.
• Adult product in children under 12 years.
• Children's product in children under 6 years.
• Hereditary fructose intolerance; the adult formulation also excludes relevant glucose-galactose malabsorption or sucrase-isomaltase insufficiency.

Monitoring

• Review unexpected excitation, confusion, hallucinations, urinary retention, visual disturbance, cardiac symptoms or excessive sedation.
• Reassess persistent or worsening cough.
• During breastfeeding exposure, monitor the infant for unusual sleepiness, poor feeding, irritability and inadequate weight gain.

Clinical pharmacology

Diphenhydramine is a centrally distributed H1-antihistamine with antitussive and anticholinergic activity. Levomenthol has mild local anaesthetic and decongestant activity.

Formulation and product differences

• The adult and older-child syrup is clear red and contains sucrose, liquid glucose, ethanol, Ponceau 4R, benzyl alcohol, sodium and sodium benzoate.
• The children's syrup is clear and colourless, contains sorbitol, ethanol, sodium and sodium benzoate, and contains no sucrose or artificial dye.
• Licensed indications and permitted ages differ.