benzalkonium chloride: clinical use

Prescribing considerations

• Confirm that the presentation is consistent with pityriasis capitis or another seborrhoeic scalp condition rather than psoriasis, contact dermatitis or fungal infection.
• Use is external and limited to the scalp; avoid ocular exposure.
• Discontinue and reassess if irritation develops, symptoms worsen or improvement is inadequate.
• Sodium benzoate may cause local irritation and may increase jaundice in newborn babies.

Contraindications and cautions

• Hypersensitivity to benzalkonium chloride or any excipient.

Monitoring

• Assess clinical response and local tolerability; no laboratory monitoring is specified.
• Review the diagnosis if scaling, erythema or pruritus persists or worsens.

Clinical pharmacology

A cationic surface-active germicide that adsorbs onto dry scales. Its interaction with the anionic foaming agent assists scale removal, while alteration of microbial cell-membrane permeability provides mild antiseptic activity. The licensed effect is superficial at the outer stratum corneum.

Formulation and product differences

• The selected product is a clear, colourless to pale-yellow viscous wash-off shampoo.
• It contains sodium benzoate and an anionic foaming agent; indications and precautions should not be transferred automatically to other benzalkonium chloride formulations.