Terbinafine: Nursing Drug Guide, Hepatotoxicity & Monitoring

Oral terbinafine is widely known by the brand name Lamisil and is available as oral tablets per institution formulary. Topical terbinafine products exist for dermatophyte infections but are not interchangeable with systemic oral therapy for nail disease.

Verify the MAR shows oral terbinafine 250 mg—not topical gel or cream—when systemic therapy is ordered for nail disease. Topical Lamisil products are a different formulation and duration.

Oral terbinafine tablets are FDA-indicated for dermatophyte onychomycosis of the fingernails or toenails (tinea unguium). Labeling advises obtaining nail specimens (KOH, fungal culture, or biopsy) to confirm diagnosis before starting therapy.

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Safety and efficacy for onychomycosis have not been established in pediatric patients per the reviewed prescribing information.

Terbinafine is an allylamine antifungal that inhibits squalene epoxidase, blocking ergosterol synthesis in fungal cell membranes and causing intracellular squalene accumulation. It is fungicidal against many dermatophytes. Terbinafine is also a CYP2D6 inhibitor, which contributes to clinically relevant drug interactions.

Oral terbinafine is given once daily without regard to meals. Match duration to nail versus skin infection and verify pretreatment liver tests before day 1.

Missed dose: Give when remembered unless near the next dose; do not double doses. For multi-week nail regimens, document missed doses and notify prescriber if adherence gaps are significant.

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Pretreatment checks

• Pretreatment ALT and AST required before initiating oral terbinafine
• History of allergic reaction to oral terbinafine (including anaphylaxis)
• Active or chronic liver disease—contraindicated per labeling
• Concurrent fluconazole, warfarin, rifampin, cimetidine, and other CYP2D6 substrates

Contraindications

• History of allergic reaction to oral terbinafine, including anaphylaxis
• Chronic or active liver disease

Important interactions

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Route: Oral tablet per medication administration policy

• Confirm pretreatment ALT/AST on chart before first dose
• May give with or without food
• Verify 250 mg oral tablet—not topical product—on the MAR
• Document week of therapy for long nail courses (6 or 12 weeks) to align with LFT monitoring schedule

• Gradual improvement in tinea skin lesions over weeks of daily therapy
• For onychomycosis, healthy nail growth may not be visible until months after completing therapy—lack of early cosmetic change does not mean hepatotoxicity monitoring can stop mid-course
• Mycologic cure is assessed by prescriber with follow-up examination or culture per plan

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Accidental doses up to 5 g have been reported without serious adverse reactions. Overdose may cause nausea, vomiting, abdominal pain, dizziness, rash, frequent urination, and headache. Management is supportive; no specific antidote is listed in prescribing information.

Nursing actions

• Stop further doses and notify prescriber, pharmacist, and poison control or toxicology services per facility protocol
• Monitor mental status, liver function, and vital signs
• Provide supportive care for GI and neurologic symptoms

Antidote: Not specified in the reviewed prescribing information — treatment is supportive.

Healthy nail growth may not look improved for months after completing oral terbinafine—lack of early cosmetic change does not justify stopping therapy early or skipping LFT monitoring mid-course. Finish the full 6- or 12-week order unless hepatotoxicity or prescriber hold rules apply.

• Terbinafine vs terbutaline — sound-alike risk; verify antifungal indication on MAR
• Oral Lamisil vs topical terbinafine — onychomycosis requires oral systemic therapy; topical products are not equivalent for nail infection
• Terbinafine vs itraconazole / fluconazole — different antifungal classes and monitoring profiles; confirm correct agent on order
• 250 mg daily × 6 weeks vs × 12 weeks — fingernail versus toenail duration errors extend hepatotoxicity exposure
• Perform medication reconciliation to catch duplicate systemic antifungals or interacting CYP drugs

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Stop oral terbinafine and escalate when serious hepatotoxicity or other life-threatening reactions develop.

• Jaundice, dark urine, clay-colored stools, or persistent RUQ pain with rising ALT/AST
• Clinical hepatitis, ascites, or signs of liver failure
• Stevens-Johnson syndrome or toxic epidermal necrolysis (mucosal involvement, widespread painful rash)
• Anaphylaxis or angioedema after prior terbinafine exposure
• Severe neutropenia or febrile illness with low white cell count
• New severe depressive symptoms or suicidal ideation

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Monitor

• Pretreatment ALT and AST (and full liver function tests when ordered) before therapy begins
• Periodic LFTs during therapy per prescriber and labeling recommendations
• Clinical signs of liver injury: nausea, RUQ pain, jaundice, fatigue, dark urine
• CBC when neutropenia is suspected; mood and rash symptoms throughout long courses

Document

• Baseline and follow-up LFT values with dates
• Week of therapy (especially toenail 12-week courses)
• Hold events, prescriber notification, and patient teaching on hepatotoxicity warning signs

• Take 250 mg once daily for the full ordered weeks—even if nails still look abnormal early in therapy
• Report yellow skin or eyes, dark urine, persistent nausea, abdominal pain, unusual bruising, severe rash, or mood changes immediately
• Taste or smell changes can occur and may not resolve after stopping the drug
• Do not start if pregnant or breastfeeding without prescriber discussion; labeling does not recommend initiation in pregnancy or nursing
• Tell all clinicians you take terbinafine before new prescriptions are added

Do not give and contact the prescriber or pharmacist when:

Hold parameters may vary by institutional protocol. Follow prescriber orders, pharmacy guidance, and facility policy.

Practice NCLEX-style clinical judgment practice for terbinafine hepatotoxicity using a tabbed case (MAR, labs, vitals, nursing notes) for week 8 of toenail onychomycosis therapy with rising ALT/AST, then work through priority action, cue recognition, trend interpretation, matrix urgency, clinical judgment, and documentation cloze—recognise cues → analyse → prioritise → act → evaluate outcomes.

This medication guide is written and reviewed using NurseOnShift editorial and clinical review standards.

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Educational use only. This content does not replace clinical judgment, prescriber orders, pharmacist guidance, product labeling, or institutional protocols.