Nail fungus

Dr. Eileen Murray MD FRCPC (biography and disclosures)

Disclosure: Served as a consultant for the pharmaceutical industry and participated in clinical research evaluating new therapies for psoriasis and atopic dermatitis. Mitigating potential bias: Treatments or recommendations in this article are unrelated to products/services/treatments involved in disclosure statements.

What I did before

Fungal infections particularly of the feet are a common problem. If only the skin is involved topical treatment with any of the antifungal creams works well. However, often fungal infections are ignored by patients and chronic skin infection can lead to infection of the nails. Older adults and those individuals who are atopic (previous history of asthma, hay fever, hives or atopic dermatitis) are at greater risk of having chronic tinea pedis and more frequently develop nail infection.

The nail changes produced by psoriasis mimic clinically the changes produced by fungal infection. So it is necessary to make sure that your patient’s nail disease is not psoriasis. Yeast infections are the most common fungal pathogens in fingernails but yeasts as well as dermatophytes and moulds infect toenails.

In order to rule out psoriasis and to determine which antifungal drug to use, the fungal organism (dermatophyte, yeast, or mould) must be identified. It is therefore necessary to culture the nail. To do this a sample of the infected nail is obtained and sent to the laboratory for examination and culture. A report is received from the lab usually within a week, after a preliminary examination of the material using a stain to highlight hyphae (Potassium hydroxide or PAS) reporting the presence or absence or hyphae in the sample. Fungal organisms grow slowly so identification of the specific fungal organism will not be received from the lab for about 6 weeks.

If the preliminary report shows hyphae, the patient likely has a fungal infection but that does not provide enough information to initiate treatment. To choose the most effective antifungal agent it is necessary to know the exact organism.

So if I suspected a nail infection I would take a sample of the nails with a sterile nail clipper and give the patient a follow-up appointment in 6 weeks’ time. However, this method did not work well, even in patients who had severe and obvious disease the culture results were often negative. This meant sending another sample and waiting another 6 weeks or resorting to treating blindly. Anti-fungal medications are expensive and treatment times are lengthy, which is an obvious disadvantage to this approach.

What changed my practice

Part of my practice includes clinical research. We participated in studies to confirm the efficacy and safety of several of the new antifungal medications. In order for subjects to be enrolled in the study we had to know specifically the organism that was infecting the nails. My research nurse would see each prospective subject. She soaked their feet in warm water, clipped as much from each damaged nail as possible and also included all the extra material from underneath each of the nails. This process took 20 to 30 minutes but almost all of the cultures of the material she sent were positive.

What I do now

This made me rethink my usual office procedure. I did not have the staff or the time to do what the research nurse did but the patients could make the time. So instead of spraying my office with hard dry nail clippings, I gave each patient a sterile urine specimen bottle labelled with their name and instructed them to let their nails grow longer (most patients have trimmed their nails before seeing you) and immediately following a hot bath or shower to clip each damaged nail, dig under the nail with a file and put all material into the bottle and return it to my office. The number of positive cultures went up dramatically.

Systemic medications recommended for treating severe widespread skin infection or nails infected with one of fungal organisms:

1. Terbinafine: 250mg tablets daily (or 125mg twice daily) for 6 weeks for fingernails, 3 to 6 months for toenails. Terbinafine is only effective for dermatophyte infections

2. Itraconazole is the preferred treatment for yeasts or nondermatophyte moulds. It is not quite as effective for dermatophyte infection as terbinafine but still has good efficacy. Pulsed dosing is recommended: 200mg tablets twice daily for one week each month for two months (fingernails) or three months (toenails). There are fewer side effects with pulsed treatment.

Both drugs are well tolerated. Drug interactions are more common with itraconazole than with terbinafine. One absolute contraindication: do not use itraconazole in patients with a history of ventricular dysfunction. Costs for either treatment are up to $100.00, for 30 days.

Topical medications: There are two topical preparations available to treat nails. Ciclopirox olamine 8% nail lacquer and efinaconazole 10% solution. The efinaconazole solution penetrates better, and is more effective, 17% vs 7%. However daily application for 48 weeks is required for optimal results from either and the cost is up to $100.00, for each 30 days. They work best on superficial white fungal disease. Use them to treat patients unable to use systemic treatment, for infected fingernails or as an adjunct therapy to improve the outcome or shorten systemic treatment time for toenails.

Practice Tip: Once you decide to begin treatment, a good way to monitor the progress and the efficacy of the treatment is to cut a shallow groove at the proximal border of the infected area. This way you can determine within a month if the treatment is working. Toe nails grow only half as quickly as fingernails so it is much harder to judge clinical improvement without the groove.

References:

1. Wolverton SE. Comprehensive Dermatologic Drug Therapy. 3rd Edition. Saunders; 2013: pp98-120 (systemic), pp460-472 (topical). (Request with CPSBC or view UBC)
   * Gupta AK. Systemic antifungal agents. Comprehensive Dermatologic Drug Therapy. 9, 98-120.e3
   * Phillips RM, Rosen T. Topical antifungal agents. Comprehensive Dermatologic Drug Therapy. 37, 460-472.e5
2. RxTx Mobile https://www.cma.ca/En/Pages/cps-mobile-app.aspx and https://www.pharmacists.ca/products-services/rxtxmobile/

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Nail fungus

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