terbinafine hydrochloride: clinical use

Prescribing considerations

• Confirm a susceptible fungal diagnosis before systemic treatment, particularly for nail disease.
• Review hepatic and renal history, interacting medicines, pregnancy, breastfeeding, psoriasis and lupus before prescribing tablets.
• Counsel patients to stop tablets and report hepatic symptoms or a progressive rash promptly.

Contraindications and cautions

• Hypersensitivity to terbinafine or a formulation excipient applies to all selected products.
• The selected tablets are contraindicated in severe hepatic or severe renal impairment and are not recommended in chronic or active hepatic disease.
• Topical products must not be used on the face, in the eyes or by mouth.

Monitoring

• Obtain liver-function tests before starting tablets and monitor periodically during treatment.
• Stop tablets and assess liver function promptly if hepatic symptoms occur or liver tests rise.
• Investigate clinically significant fever, infection, bruising or bleeding with an appropriate blood count.
• Review persistent taste or smell disturbance, weight loss, progressive rash, or new lupus or psoriasis features.

Clinical pharmacology

Oral terbinafine is well absorbed but undergoes first-pass metabolism, distributes extensively into keratin-rich skin, hair and nails, and is strongly protein bound. It is metabolised through several CYP enzymes and inhibits CYP2D6; inactive metabolites are excreted mainly in urine.

Formulation and product differences

• Tablets provide systemic exposure and carry hepatic, haematological and clinically important interaction risks.
• The selected cream is licensed for athlete’s foot and fungal groin infection in people over 16; it contains benzyl, cetyl and stearyl alcohols that may cause local reactions.
• The film-forming solution is licensed for adult athlete’s foot, contains a high proportion of ethanol, forms a persistent skin film and may burn damaged skin.
• Topical systemic exposure is low, and no drug interactions are known for the selected topical products.

Cream

Route: Cutaneous

Strengths: 1%, 1% w/w

Tablet

Route: Oral

Strengths: 250 mg