Terbinafine

Aka: Terbinafine, Lamisil, Allylamine Antifungal

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II. Indications

  1. Topical Management (Lamisil, Terbinafine HCl 1%)
    1. Resistant dermatophyte infection
    2. Tinea Pedis
    3. Tinea Cruris
    4. Tinea Corporis
    5. Tinea Versicolor
  2. Systemic Management (Terbinafine oral)
    1. Onychomycosis
      1. Highly active in vitro against dermatophytes (more than Itraconazole)
      2. Does not cover all yeast forms that cause Onychomycosis

III. Contraindications

  1. Liver Disease
  2. GFR <50 ml/min

IV. Mechanism

  1. Synthetic Allylamine Antifungal
  2. Blocks Ergosterol synthesis (key component in the fungal cell wall)
    1. Inhibits squalene epoxidase, the enzyme that converts squalene to ergosterol

V. Medications

  1. Terbinafine Oral
    1. Tablets: 250 mg
    2. Pharmacists can compound into oral suspensions for children
  2. Terbinafine Topical (Lamisil AT)
    1. Available as a 1% cream, spray or gel
    2. Minimal systemic absorption (3%)

VI. Dosing: Oral for Onychomycosis

  1. Dose
    1. Adult (and child >40 kg): 250 mg orally daily
    2. Child weight 20 to 40 kg: 125 mg (up to 187.5 mg) orally daily
    3. Child (age> 4 years) and weight <20 kg: 67.5 mg (up to 125 mg) orally daily
  2. Duration
    1. Tinea Capitis: 6 weeks (longer course if culture grows Microsporum)
    2. Fingernail Onychomycosis: 6 weeks
    3. Toenail Onychomycosis: 12 weeks

VII. Dosing: Topical for Superficial Tinea Infections

  1. Apply twice daily until resolution and for at least 1 week (up to 4 weeks)

VIII. Adverse Effects: Oral

  1. Common
    1. Headache
    2. Gastrointestinal upset (Diarrhea, Dyspepsia, Abdominal Pain)
    3. Taste Dysfunction
  2. Uncommon
    1. Rash (including Urticaria and Pruritus)
      1. Typically mild with spontaneous resolution
  3. Serious (rare)
    1. Anaphylaxis
    2. Cholestatic hepatitis
    3. Blood dyscrasia
      1. Pancytopenia
      2. Neutropenia
    4. Stevens-Johnson Syndrome
    5. Toxic Epidermal Necrolysis
    6. Drug-induced Lupus (or exacerbation of pre-existing Systemic Lupus Erythematosus)
    7. Hepatotoxicity
      1. Increased serum transaminases
      2. Significant liver injury has been reported
    8. Ocular findings
      1. Ocular lens changes
      2. Retinal changes

IX. Safety

  1. Unknown safety in Lactation (present in human milk)
  2. Pregnancy Category B
    1. However, limited safety data in human pregnancies

X. Pharmacokinetics

  1. Oral Bioavailability: High
    1. Peak serum concentrations within 2 hours
  2. Distribution
    1. Terbinafine is lipophilic and keratophilic
    2. Reaches high concentrations in the Stratum Corneum, sebum, hair and nails
      1. Nail clippings contain Terbinafine within 1 week of first dose
      2. Nail clippings contain Terbinafine for up to 36 weeks after last dose
  3. Hepatic Metabolism
    1. NOT metabolized by Cytochrome P450
  4. Excreted in urine and stool
    1. Decreased clearance in renal and hepatic Impairment

XI. Drug Interactions

  1. CYP2D6 Inhibitor
  2. Terbinafine increases other drug levels (esp. as CYP2D6 Inhibitor)
    1. Warfarin (may increase INR)
  3. Terbinafine decreases other drug levels
    1. Cyclosporine (15% reduction in levels)
  4. Drugs that increase Terbinafine levels
    1. Cimetidine
    2. Fluconazole
  5. Drugs that decrease Terbinafine levels
    1. Rifampin (doubles clearance rates)

XII. Monitoring: Oral

  1. Protocol
    1. Baseline AST and ALT
    2. Repeat CBC after 6 weeks of continuous use if Immunodeficiency
      1. Discontinue if Neutrophil Count <1000 cells/mm3
    3. New guidelines do not require repeat LFT testing routinely
      1. Obtain repeat testing if higher risk of liver abnormality, concurrent use of Hepatotoxic Medications, or symptoms
      2. In past, LFTs have been monitored every 4 to 6 weeks
      3. Stop agent if AST or ALT increased >2x normal
  2. Labs
    1. Complete Blood Count and Platelet Count (if Immunodeficiency)
    2. Aspartate Aminotransferase (AST)
    3. Alanine Aminotransferase (ALT)
    4. Serum Creatinine

XIII. Resources

  1. Terbinafine Tablet (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=6dc279cc-9861-4fa8-8083-ca3b3c57b513

XIV. References

  1. (2012) Med Lett Drugs Ther 10(120): 61-8 [PubMed]
  2. (1996) Med Lett Drugs Ther 38(981): 72-4 [PubMed]
  3. Ely (2014) Am Fam Physician 90(10): 702-10 [PubMed]
  4. Gupta (1999) J Am Acad Dermatol 41:237-49 [PubMed]
  5. Friedlander (1999) Pediatr Infect Dis J 18(2):205-10 [PubMed]
  6. McClellan (1999) Drugs 58(1):179-202 [PubMed]
  7. Perez (1999) Mycoses 43:79-83 [PubMed]

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Cost: Medications

terbinafine (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
TERBINAFINE 1% CREAM Generic OTC $0.27 per gram
TERBINAFINE HCL 250 MG TABLET Generic $0.16 each
FPNotebook does not benefit financially from showing this medication data or their pharmacy links. This information is provided only to help medical providers and their patients see relative costs. Insurance plans negotiate lower medication prices with suppliers. Prices shown here are out of pocket, non-negotiated rates. See Needy Meds for financial assistance information. GoodRx is another tool for finding lower drug prices.

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