A-Z Drug Facts > Terbinafine

Terbinafine

Pronouncation: (TER-bin-a-feen)
Class: Anti-infective, Antifungal

Trade Names:
Lamisil
- Tablets 250 mg

Trade Names:
Lamisil AT
- Cream 1%

Apo-Terbinafine (Canada)
Gen-Terbinafine (Canada)
Novo-Terbinafine (Canada)
PMS-Terbinafine (Canada)

Pharmacology

Inhibits squalene epoxidase, resulting in ergosterol deficiency and a corresponding accumulation of squalene within the fungal cell leading to fungal cell death.

Pharmacokinetics

Absorption

Absorption from oral terbinafine is greater than 70%; bioavailability is about 40%. Terbinafine C _max is 1 mcg/mL, T _max occurs 2 h after a 250 mg dose. AUC is 4.56 mcg•h/mL and is increased less than 20% with food. At steady state in comparison to single dose, C _max is 25% higher and AUC is increased 2.5 times.

Distribution

Terbinafine is more than 99% protein bound and there are no specific binding sites. It is distributed to the sebum and skin.

Metabolism

Prior to excretion, terbinafine is extensively metabolized. There are no major metabolites that have antifungal activity similar to terbinafine.

Elimination

Terbinafine t _½ is 200 to 400 h and the drug is about 70% eliminated in the urine.

Special Populations

Renal Function Impairment

In renal function impairment (CrCl approximately 50 mL/min), terbinafine Cl is decreased 50%.

Hepatic Function Impairment

In hepatic cirrhosis, terbinafine Cl is decreased 50%.

Indications and Usage

Treatment of onychomycosis of the toenail or fingernail caused by dermatophytes.

Topical

Interdigital tinea pedis, tinea cruris, or tinea corporis caused by E. floccosum , T. mentagrophytes , or T. rubrum .

Unlabeled Uses

Cutaneous candidiasis, pityriasis (tinea) versicolor (topical).

Contraindications

Preexisting liver disease or renal function impairment (CrCl up to 50 mL/min).

Dosage and Administration

Adults

PO 250 mg/day for 6 wk for fingernail onychomycosis; 250 mg/day for 12 wk for toenail onychomycosis.

Topical Apply to affected areas and surrounding skin once or twice daily.

Storage/Stability

Store tablets below 77°F. Keep tightly closed and protect from light.

Drug Interactions

Caffeine

Terbinafine decreases the Cl of IV caffeine 19%.

Cimetidine

Terbinafine Cl is decreased 33% by cimetidine.

Cyclosporine

Terbinafine increases the Cl of cyclosporine 15%.

Dextromethorphan

Plasma dextromethorphan concentrations may be elevated, increasing the pharmacologic effects and adverse reactions. Terbinafine inhibits dextromethorphan metabolism via the CYP-450 2D6 enzyme.

Rifampin

Terbinafine Cl is increased 100% by rifampin.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Dermatologic

Pruritus; rash; urticaria.

GI

Abdominal pain; diarrhea; dyspepsia; flatulence; nausea.

Miscellaneous

Headache; liver enzyme abnormalities; taste disturbance; visual disturbance.

Precautions

Pregnancy

Category B .

Lactation

Excreted in breast milk.

Children

Safety and efficacy not established.

Renal Function

Do not use in patients with renal function impairment (CrCl up to 50 mL/min).

Hepatic Function

LFTs are recommended if used more than 6 wk and in the presence of possible signs of liver dysfunction. Insufficient information on risks in presence of preexisting liver or renal disease. Transient decreases in absolute lymphocyte counts have occurred. Risk to immune deficient patients is unknown. Severe neutropenia has been reported.

Ophthalmic

Changes in the ocular lens and retina have been reported.

Patient Information

• Review dosing schedule and prescribed length of therapy with patient: 1 tablet daily for 6 wk (fingernail onychomycosis) or 12 wk (toenail onychomycosis).
• Instruct patient to take 1 tablet daily without regard to meals.
• Advise patient that if a dose is missed, take it as soon as possible, but if close to the next dose, do not double up and take the next dose as scheduled.
• Emphasize importance of completing full course of therapy, even if signs and symptoms of infection have disappeared.
• Warn patient to report any of the following to their health care provider immediately: skin rash, persistent nausea, vomiting, right upper abdominal pain, fatigue, anorexia, dark urine, yellowing of the skin or eyes.

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