Home ► Publications ► Prescriber Update ► Article Search ► Spotlight on Terbinafine

Published: 13 December 2018

Publications

Spotlight on Terbinafine

This article is more than five years old. Some content may no longer be current.

Prescriber Update 39(4): 50–52
December 2018

Key Messages

Ensure use of oral terbinafine is appropriate when prescribing it for fungal infections.
Duration of oral terbinafine treatment depends on the indication and the severity of the fungal infection.
Check for drug interactions before starting a patient on oral terbinafine.

The spotlight series continues with this article on terbinafine. Key information on terbinafine and adverse reaction reporting in New Zealand are described.

Please refer to the medicine data sheets for full prescribing information (www.medsafe.govt.nz/Medicines/infoSearch.asp).

Background information

Terbinafine is an allylamine medicine used to treat fungal infections and is particularly effective against dermatophytes (tinea infections)^1,2.

In New Zealand, terbinafine is available in topical preparations (cream, gel, solution and spray) and oral formulation (tablets)³ . This article focuses on oral terbinafine.

Appropriateness of oral treatment

Prescribers should ensure that the presenting infection/condition is caused by susceptible fungal organisms before prescribing oral terbinafine⁴ , and that the site, severity or extent of the fungal infection warrant the use of a systemic antifungal medicine.

For less extensive or less severe fungal infections it may be more appropriate to treat with a topical antifungal medicine first.

Use of oral terbinafine is associated with a number of rare, but potentially serious adverse reactions⁴ . The reactions reported to the Centre for Adverse Reactions Monitoring are summarised later in this article.

Indications

Oral terbinafine is indicated in New Zealand for the following conditions:^2,5

onychomycosis (fungal infection of the nail) caused by dermatophyte fungi
tinea capitis
treating tinea pedis, tinea cruris or tinea corporis where oral therapy is appropriate due to the site, severity or extent of the infection
fungal infections of the skin caused by the genus Candida (eg, Candida albicans) where oral therapy is appropriate due to the site, severity or extent of the infection.

Unlike topical terbinafine, oral terbinafine is not effective in the treatment of pityriasis versicolor^2,6.

Recommended dose and duration of oral treatment

The standard adult dose is 250 mg per day² .

The duration of oral terbinafine treatment differs according to the indication and the severity of the infection (Table 1). Following mycological cure, it may take a further few weeks or months for the signs and symptoms of the infection to resolve² .

Table 1: Recommended treatment duration of oral terbinafine according to indication

Skin infections	Recommended treatment duration
Cutaneous candidiasis	2–4 weeks
Tinea corporis, tinea cruris	2–4 weeks
Tinea pedis (interdigital, plantar/moccasin type)	2–6 weeks
Hair and scalp infections	Recommended treatment duration
Tinea capitis	4 weeks
Onychomycosis	Recommended treatment duration
Fingernail onychomycosis	6 weeks
Toenail onychomycosis	12 weeks*

* Longer treatment may be required in patients with poor nail outgrowth.

Source: REX Medical Limited. 2017. Deolate 250 mg tablets New Zealand Data Sheet 11 September 2017. URL: www.medsafe.govt.nz/profs/Datasheet/d/deolatetab.pdf (accessed 8 October 2018).

Considerations in special populations

Hepatic impairment

Oral terbinafine is not recommended for patients with active or chronic liver disease. Assessment of pre-existing liver disease should be completed before prescribing oral terbinafine² .

Renal impairment

Only use oral terbinafine in renally-impaired patients if there is no other alternative. Patients with impaired renal function (eg, creatinine clearance [CrCl] less than 50 mL/min or serum creatinine greater than 300 µmol/L) should take half the normal dose of oral terbinafine. There is no information on use in patients with CrCl less than 20 mL/min² .

Pregnancy and lactation

Clinical experience in pregnant women is limited. Oral terbinafine should not be used during pregnancy unless the expected benefits outweigh any expected risks² .

Oral terbinafine should not be administered to mothers who are breastfeeding as terbinafine is excreted into breast milk² .

Elderly patients

Consider the potential for pre-existing kidney or liver impairment in the elderly² .

Children

There is no data available on oral terbinafine use in children aged under 2 years who weigh less than 12 kg² . See the data sheet for dosing recommendations in children.

Medicine interactions

Examples of medicines that interact with terbinafine are shown in Table 2.

Terbinafine is metabolised by at least seven CYP450 enzymes, of which CYP1A2, CYP3A4, CYP2C8, CYP2C9 and CYP2C19 are the most important^2,7. Terbinafine exposure may be altered when co-administered with medicines that inhibit or induce these enzymes.

Terbinafine is a CYP2D6 inhibitor. Patients receiving concomitant treatment with medication primarily metabolised by this enzyme should be monitored if the interaction is likely to be clinically relevant (eg, some beta-blockers, Class 1C anti-arrhythmics, Type B monoamine oxidase inhibitors, selective serotonin reuptake inhibitors and tricyclic antidepressants)² .

The extent of the inhibition is such that CYP2D6 extensive metabolisers may find that their response to treatment with dextromethorphan or codeine is similar to that of a poor CYP2D6 metaboliser² .

Table 2: Examples of medicine interactions with terbinafine

Medicines that may increase the plasma concentration or the effect of terbinafine	Cimetidine Fluconazole Ketoconazole Amiodarone
Medicines that may reduce the plasma concentration or the effect of terbinafine	Rifampicin
Terbinafine may increase the plasma concentration or the effect of	Caffeine Medicines metabolised by CYP2D6, including some beta blockers, Class 1C anti-arrhythmics, Type B monoamine oxidase inhibitors, selective serotonin reuptake inhibitors, tricyclic antidepressants*
Terbinafine may reduce the plasma concentration or the effect of	Ciclosporin

* Monitor patients who are taking these medicines concomitantly with terbinafine.