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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
The oral antifungal drug terbinafine appears to be slightly better than alternative ‘azole’ drugs for treating fungal toenail infection. Fifty-eight percent of people had a normal nail appearance after a treatment course compared with 47% taking ‘azoles’. Both drug classes were more effective than placebo and had similar side effects.
Current guidelines recommend terbinafine or itraconazole as first-choice treatments, but consider terbinafine more effective. However, systematic reviews on the topic were outdated. This Cochrane review updates the evidence, pooling the findings from 43 trials comparing oral antifungals with each other or placebo.
The results support guidelines recommending terbinafine as the first choice for treatment unless contraindicated.
Antifungals are available in oral and topical forms (applied to the nail). Topical antifungals have long been thought less effective, but the review did not gather evidence to confirm this.
Why was this study needed?
Fungal nail infection is thought to affect somewhere between two and 14% of the adult population. It is most common in older people and those with diabetes.
Most cases of toenail infections (about 80%) are due to dermatophyte fungi such as Trichophyton; other fungi include Aspergillus, Scopulariopsis, Fusarium and Alternaria. Some are highly resistant to treatments.
Toenail infections have a low complication rate, but they may affect the function of the nail and quality of life. Topical treatments are commonly used, but they have a low success rate. The most common oral antifungal treatments are terbinafine and itraconazole (an azole drug). Drug treatment can be costly to the NHS as a standard course of oral treatment is three months, and it may take as long as six months to a year to treat infection successfully.
Though oral antifungal drugs are thought to be effective, systematic review evidence is outdated. The researchers wanted to perform an up-to-date review to find out which oral antifungal was most effective for toenail infections to help guide evidence-based treatment.
What did this study do?
This systematic review pooled 43 randomised controlled trials including 9,730 people and comparing oral antifungal treatment with another active treatment or placebo.
Seven trials compared terbinafine with placebo, nine compared itraconazole with placebo and 17 compared these two drugs with each other. Other studies assessed griseofulvin and other ‘azole’ drugs. Treatment duration ranged from four months to two years.
Lack of blinding of researchers and/or participants and potential for biased allocation to treatment group were common across studies. Over half the trials were published before the year 2000. Most were carried out in outpatient dermatology settings in Western countries, but only three were conducted in the UK. However, the evidence was assessed as high quality for most outcomes.
What did it find?
- Terbinafine was more effective than azoles. Forty-seven percent of people who took azoles were cured, based on normal nail appearance, compared with 58% who took terbinafine (relative risk [RR] 0.82, 95% confidence interval [CI] 0.72 to 0.95; 15 studies, 2,168 people). People taking azoles were similarly less likely to achieve a mycological cure as defined by negative results on microscopy or culture: 53% vs 68% with terbinafine (RR 0.77, 95% CI 0.68 to 0.88; 17 studies, 2,544 people). Adverse effects and recurrence rates were similar between the two drugs.
- In placebo comparisons, terbinafine was more effective. Forty-eight percent achieved a clinical cure compared with only 6% of the placebo group (RR 6.00, 95% CI 3.96 to 9.08; 8 studies, 1,006 people). The mycological cure rate was 59% vs 17% with placebo (RR 4.53, 95% CI 2.47 to 8.33) though there was high variability between individual studies for this outcome. Gastrointestinal symptoms and respiratory infections were among side effects reported with terbinafine, but these were still not significantly more common than with placebo.
- Azoles were also more effective than placebo with 31% achieving a clinical cure vs 14% in the placebo group (RR 22.18, 95% CI 12.63 to 38.95; 9 studies, 3,440 people). They were also more likely to achieve mycological cure (35% vs 7%; RR 5.86, 95% CI 3.23 to 10.62), but as with terbinafine, there was high variability between studies for this outcome.
- There was low-quality evidence that griseofulvin was less effective than terbinafine regarding clinical cure (RR 0.32, 95% CI 0.14 to 0.72; four studies, 270 people) and mycological cure (RR 0.64, 95% CI 0.46 to 0.90; five studies, 465 people). There was no statistically significant difference in the likelihood of achieving clinical or mycological cure with griseofulvin compared with an azole.
- There was very low-quality evidence from a single study (176 people) that the combination of terbinafine plus an azole was more effective than terbinafine alone (clinical cure: RR 1.41, 95% CI 1.01 to 1.97; mycological cure: RR 1.41, 95% CI 1.08 to 1.83).
What does current guidance say on this issue?
The British Association of Dermatologists (2014) suggests either terbinafine or itraconazole as first options for the treatment of fungal nail infection in both adults and children. However, they say that unless there are contraindications terbinafine is preferred based on its higher efficacy and tolerability.
Griseofulvin has lower efficacy, higher relapse rates and more side effects than terbinafine or itraconazole but remains an option if these drugs are ineffective or not tolerated.
What are the implications?
These results support guideline recommendations that terbinafine is the most effective oral drug and should be considered the first-choice in fungal nail infection.
Topical treatments may still be in widespread use, particularly when purchased over-the-counter. This study was not able to assess or confirm their comparative lack of efficacy when compared with oral treatment.
Nail infection may recur after stopping treatment, so prevention is important. Healthcare professionals should advise people to wear protective shoes in public changing rooms (e.g. swimming pools or gyms), keep their nails short, avoid sharing nail clippers and wear shoes that fit properly.
Citation and Funding
Kreijkamp-Kaspers S, Hawke K, Guo L, et al. Oral antifungal medication for toenail onychomycosis. Cochrane Database Syst Rev. 2017;(7): CD010031.
Cochrane UK and the Cochrane Skin Group are supported by the National Institute for Health research via Cochrane Infrastructure funding.
Bibliography
Ameen M, Lear JT, Madan V, et al. British Association of Dermatologists' guidelines for the management of onychomycosis 2014. Br J Dermatol. 2014;171(5):937-58.
NHS Choices. Fungal nail infections. London: Department of Health; 2015.
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