Nailderm (Terbinafine)

• Terbinafine is used to treat fungal infections of the nail and skin caused by dermatophytes, offering a systemic oral option for clinicians.
• Onychomycosis: clears the fungal infection of the toenail or fingernail, leading to restoration of nail appearance and prevention of further spread.
• Dermatophyte skin infections: treats conditions such as tinea corporis, tinea pedis and tinea cruris by eliminating the dermatophyte organisms, relieving itching, scaling and redness.
• Other superficial fungal infections: may be used for mild cases of cutaneous candidiasis when indicated by a clinician.

• Terbinafine acts by inhibiting the fungal enzyme squalene epoxidase, a key step in the biosynthesis of ergosterol, an essential component of fungal cell membranes. Blockade of this pathway leads to accumulation of squalene, which is toxic to the fungus, and depletion of ergosterol, compromising membrane integrity and resulting in fungal cell death. The selective inhibition provides a high therapeutic index because human cells lack the target enzyme.

Terbinafine may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Gastrointestinal discomfort: nausea, abdominal pain or diarrhea.
• Headache: mild to moderate intensity.
• Skin rash: pruritic erythema.
• Taste disturbance: dysgeusia or loss of taste.
• Elevated liver enzymes: transient increase in ALT/AST.

Serious or Rare Side Effects

• Hepatotoxicity: severe liver injury or hepatitis.
• Stevens‑Johnson syndrome: severe skin and mucous membrane reaction.
• Blood dyscrasias: agranulocytosis or aplastic anemia.
• Severe cutaneous adverse reactions: toxic epidermal necrolysis.

Before initiating Terbinafine therapy, clinicians should evaluate patient-specific factors and monitor for potential risks.

• Assess liver function: obtain baseline hepatic enzymes and repeat as clinically indicated.
• Avoid in known hypersensitivity: discontinue if allergic reaction occurs.
• Use caution in renal impairment: dose adjustment may be required in severe renal dysfunction.
• Monitor for drug interactions: review concomitant medications that affect hepatic metabolism.
• Store at room temperature: keep in the original packaging, protect from moisture and direct sunlight.

Terbinafine can interact with several medicines, altering its concentration or that of the co‑administered drug.

Major Interactions (Avoid)

• Azole antifungals (e.g., itraconazole): increased risk of hepatotoxicity.
• Rifampin: induces metabolism, reducing terbinafine plasma levels.
• Cimetidine: may raise terbinafine exposure and liver enzyme levels.
• Isoniazid: additive hepatic toxicity when combined.

Moderate Interactions (Monitor Closely)

• Warfarin: terbinafine may potentiate anticoagulant effect, increasing INR.
• Oral contraceptives: reduced efficacy reported, consider alternative contraception.
• Antidepressants (SSRIs): possible QT interval prolongation, monitor ECG.