terbinafine

Interferes with fungal cell wall synthesis (ergosterol biosynthesis) by inhibiting the enzyme squalene epoxidase.

Therapeutic effects:

Fungal cell death.

Spectrum:

Active against dermatophytes and other fungi.

Pharmacokinetics ⬆ ⬇

Absorption: 70–80% absorbed after oral administration.

Distribution: Extensively distributed; penetrates dermis and epidermis; concentrates in stratum corneum, hair, scalp, and nails. Enters breast milk.

Protein Binding: 99%.

Metabolism/Excretion: Extensively metabolized by the liver by CYP1A2, CYP2C9, CYP2C19, and CYP3A4.

Half-Life: Plasma—22 days; longer from skin and nails.

Time/Action Profile ⬆ ⬇

(antifungal tissue levels)

ROUTE	ONSET	PEAK	DURATION
PO	several days	days–wk	several wk

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Chronic or active liver disease;
Heart failure or left ventricular dysfunction.

Use Cautiously in:

History of alcoholism;
Renal impairment (dose ↓ recommended for CCr <50 mL/min);
OB: Safety not established in pregnancy;
Lactation: Use while breastfeeding only if maternal benefit outweighs potential risk to infant;
Pedi: Safety and effectiveness not established in children.

Adv. Reactions/Side Effects ⬆ ⬇

CV: heart failure

Derm: DRUG REACTION WITH EOSINOPHILIA AND SYSTEMIC SYMPTOMS (DRESS), STEVENS-JOHNSON SYNDROME, TOXIC EPIDERMAL NECROLYSIS, itching, rash

GI: HEPATOTOXICITY, anorexia, diarrhea, nausea, stomach pain, vomiting, drug-induced hepatitis, smell disturbance, taste disturbance

Hemat: hemolytic uremic syndrome, neutropenia, pancytopenia, thrombotic thrombocytopenic purpura

Neuro: depression, headache

Resp: cough, nasopharyngitis

Misc: fever

Interactions ⬆ ⬇

Drug-drug:

Alcohol or other hepatotoxic agents may ↑ risk of hepatotoxicity.
Rifampin may ↓ effectiveness.
Fluconazole and cimetidine may ↑ levels.
May ↑ effects of CYP2D6 substrates including tricyclic antidepressants, selective serotonin reuptake inhibitors, beta-blockers, flecainide, and propafenone.

Drug-Natural Products:

↑caffeine levels and side effects with caffeine-containing herbs (cola nut, guarana, mate, tea, coffee).

Route/Dosage ⬆ ⬇

PO (Adults ): 250 mg once daily for 6 wk for fingernail infection or 12 wk for toenail infection.

Availability ⬆ ⬇

(Generic available)

Tablets: 250 mg

Assessment ⬆ ⬇

Assess for signs and symptoms of infection (nail beds, scalp) before and periodically during therapy.
Specimens for culture should be taken before instituting therapy. Therapy may be started before results are obtained.
Monitor for depression periodically during therapy.
Assess for rash periodically during therapy. May cause Stevens-Johnson syndrome. Discontinue therapy if severe or if accompanied with fever, general malaise, fatigue, muscle or joint aches, blisters, oral lesions, conjunctivitis, hepatitis and/or eosinophilia.

Lab Test Considerations:

Monitor CBC in patients receiving therapy for >6 wk. Discontinue if abnormal values occur.
- Monitor AST and ALT prior to, and periodically during therapy. Terbinafine should be discontinued if symptomatic elevations occur.
- If signs of secondary infection occur, monitor neutrophil count. If <1000/mm³, discontinue treatment.
- May cause ↓ absolute lymphocyte count.
- Monitor serum potassium. May cause hypokalemia.

Implementation ⬆ ⬇

Do not confuse Lamisil (terbinafine) with Lamictal (lamotrigine).
PO: May be administered without regard to food.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take medication as directed, for the full course of therapy, even if feeling better. Doses should be taken at the same time each day. Advise patient to read Medication Guide before starting therapy and with each Rx refill in case of changes.
Instruct patient to notify health care professional immediately if signs and symptoms of liver dysfunction (unusual fatigue, anorexia, nausea, vomiting, upper right abdominal pain, jaundice, dark urine, or pale stools) depression, or rash occur. Terbinafine should be discontinued.
May cause disturbance in taste and smell. Advise patient to notify health care professional if this or poor appetite, weight loss, or anxiety occur.
Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
Advise patient to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇