Preventing and treating Trichophyton indotineae

Prevention

• Specific recommendations to prevent T. indotineae infection do not exist, but physicians can educate patients about strategies for preventing dermatophyte infections in general.

• Health care professionals should use Standard Precautions when caring for patients with possible tinea.

Empiric treatment

Because confirmatory testing may take weeks, it is reasonable to empirically start treatment for T. indotineae based on patient epidemiologic and clinical features while awaiting confirmatory testing. Potassium hydroxide (KOH) preparation of skin scrapings should be performed in clinic, whenever possible, to confirm fungal infections.¹

Treatment duration

Treatment may be anticipated to last 6–8 weeks and is given until complete clinical clearance from all infected sites and, ideally, a negative KOH preparation of skin scrapings.¹ Longer durations of therapy have been reported (up to 20 weeks) in order to achieve cure.² Relapses even with long durations of therapy have been reported.

Antifungal selection¹

Itraconazole

While there are no current international standardized treatment guidelines, first-line treatment dose is generally considered to be 100 mg/d or 200 mg/d.³

• Itraconazole has numerous drug-drug interactions due to CYP enzyme inhibition. Physicians can work with pharmacists to check for drug-drug interactions before prescribing or dispensing itraconazole.

• Itraconazole has various formulations and different recommendations for administration. Patients taking itraconazole capsules should take this medication with food and an acidic beverage (e.g., orange juice, cola) to increase absorption. Patients taking itraconazole suspension should take this medication on an empty stomach.

• Itraconazole has a black box warning for cardiac toxicity. There may be a greater risk of cardiac toxicity with higher doses of itraconazole.

• Any signs of liver disease, including jaundice, pruritus, an unexplained increase in liver function tests, and nausea or vomiting, could indicate hepatotoxicity.⁴

• Transient as well as permanent hearing loss has been reported in patients receiving treatment with itraconazole.⁵

Terbinafine

Given at higher than usual dose (250 mg twice daily) has been successfully used to treat T. indotineae in some patients, though close monitoring is recommended as this dose has not consistently shown efficacy. Clinicians may consider closer liver enzyme monitoring, though no established parameters for laboratory monitoring at higher terbinafine doses exist.

Griseofulvin and fluconazole

These are not considered first line. This is because studies from India have shown low efficacy and high minimum inhibitory concentrations for these drugs against T. indotineae. However, these medications have been used successfully in select cases and may be considered on a case-by-case basis (for example, if patients fail to improve on terbinafine, yet itraconazole is contraindicated).

Voriconazole

This drug that is normally used for invasive fungal infections, has been used in cases of itraconazole resistance, which is currently considered rare.^6,7 Voriconazole has numerous drug-drug interactions due to CYP enzyme inhibition and side effects. Voriconazole is very photosensitizing and has been associated with accelerated photo-carcinogenesis. Use of this medication should generally occur under the guidance of an infectious diseases specialist and only after confirming the patient has either failed an appropriate course of itraconazole or cannot tolerate itraconazole and has failed other antifungals.

Combination oral therapy

Combining different oral antifungals is generally not recommended.

Combination oral/topical therapy

More data are needed to establish the role of combination topical and oral antifungal medications. Dermatologists may consider such combination therapy. It is unknown whether topical antifungals may limit spread of dermatophyte spores.

Itch

Patients with T. indotineae often report extreme pruritus. In addition to antifungal treatments, clinicians should ensure that patients are not using topical corticosteroid treatments. Instead, physicians can consider recommending or prescribing antihistamines for itch.

• It is important to note that post-tinea xerosis, itch, and dermatographism are reported. Pruritus may also suggest active and ongoing dermatophytosis. Clinical evaluation is important; KOH preparation of skin scrapings can help confirm mycologic resolution.¹

Patient counseling

• The need for prolonged therapy.

• The importance of adherence to the medication and follow-up.

• The need to avoid sharing personal items and clothing.

• Clothing, towels, bedding, and similar shared items should be laundered on high heat.⁸

• The possibility of relapse or recurrence.

• Potential side effects from antifungals.

• Dermatophyte spores can be killed with common disinfectants like diluted chlorine bleach (1/4 cup per gallon water), benzalkonium chloride, or strong detergents.

• If pets are present in the home and also develop skin lesions, the pet should be evaluated by a veterinarian.

Some U.S. physicians have reported challenges with getting itraconazole approved by insurance companies. Cost Plus pharmacy* is one option for obtaining affordable antifungals for people with insurance; it also offers affordable antifungals without insurance.

Antifungal susceptibility testing (AFST) and minimum inhibitory concentration (MIC) data

The goal of AFST is to produce MIC values to guide therapy, inform epidemiological studies, and track antifungal drug resistance^9-11.

Definitions

No established breakpoints exist for antifungals in dermatophytosis

• This means you cannot look at a laboratory derived MIC value to determine whether a dermatophyte will be resistant to that antifungal.

• Currently, ECOFFs are not established for T. indotineae.

Predicting T. indotineae responsiveness

• A large body of data, largely from isolates collected from patients in India, demonstrates that a terbinafine MIC cutoff of 0.5 ug/mL can predict terbinafine-responsive isolates, and may correlate to specific point mutations in the squalene epoxidase gene.

• Mildly elevated terbinafine MIC values may indicate T. indotineae isolates with potential responsiveness to higher than standard doses of terbinafine (see above).

• Similar data is more limited for other antifungal medications (see above).

* The Academy is able to share this resource on an informational basis only. This does not represent an endorsement by the Academy. Please compare, evaluate, and consider which resources best meet your needs.

Additional resources