coal tar solution: clinical use

Prescribing considerations

• Confirm that lesions are psoriasis and assess whether topical tar is suitable for the affected site.
• Consider irritation, photosensitivity, fire risk and the uncertain risk associated with prolonged exposure.
• Coordinate use with phototherapy or radiotherapy teams.
• Use cautiously on facial skin; avoid genital and rectal application.

Contraindications and cautions

• Hypersensitivity to coal tar or an excipient
• Folliculitis or acne vulgaris
• Photosensitivity disorders, including lupus erythematosus or allergy to sunlight
• Inflamed or broken skin, open exuding wounds or local skin infection

Monitoring

• Review for irritation, photosensitivity, acne-like eruptions and delayed hypersensitivity.
• Assess clinical response and reconsider treatment if irritation persists.
• No routine laboratory monitoring is specified.
• Reassess benefit and risk if prolonged use or UVB exposure is contemplated.

Clinical pharmacology

Coal tar is an antipruritic, keratoplastic topical treatment. It reduces scaling and inflammation and slows excessive epidermal cell production; systemic pharmacokinetic data are not applicable to the selected product.

Formulation and product differences

• The selected licensed product is a smooth, mustard-coloured cutaneous emulsion that must be shaken before use.
• It contains methyl and propyl hydroxybenzoates, which can cause delayed allergic reactions, and hydrogenated polyoxyl castor oil, which can cause skin reactions.
• Contaminated fabric burns more easily; washing reduces but may not completely remove accumulated product.