INTRODUCTION
Despite the number of available treatments, not all patients
with onychomycosis are cured and recurrence (relapse or re-infection) is not uncommon, with percentages
reported in various clinical studies ranging from 10% to 53%.1 Definition of recurrence is less clear, since differentiating
relapse from re-infection remains imprecise. Relapse implies some improvement in the disease, but then a reappearance
of the same or similar clinical symptoms following treatment due to incomplete eradication of the initial infection. Re-infection usually occurs some length of time after the initial nail infection is ostensibly cured, either with the same or a different
fungal organism. When the same organism is involved, relapse or re-infection has sometimes been differentiated by an arbitrary 1 or 2-year cut-off. It has been suggested that the inability
to obtain long-term cure may be a result of genetic susceptibility,
strain type switching, emergence of drug-resistant fungal strains, or continual contact with fungal material shed from the patient at the time of active infection.1-4
Recurrence With Systemic Therapy
Data on recurrence rates are limited, primarily because most clinical studies have concentrated on 9 to 12 months’
outcome. Few studies have followed the clinical course of patients
beyond 12 months.5,6 A meta-analysis of five trials found that relapses were more common after treatment with itraconazole
(intermittent or continuous) compared to terbinafine (continuous) after long-term follow-up (more than two years after the end of therapy).7 The long-term benefits of terbinafine are probably related to its fungicidal action, compared with the fungistatic action of itraconazole.6 However, only 251 patients
were included in the meta-analysis,8-12 and the studies were not comparable in terms of outcome with only one assessing
complete cure.12 In one study, nail lacquer was applied to some patients as a prophylactic measure with no significant impact on relapse.12
A prospective, long-term study (1.25 to 7 years’ post-enrolment) in 166 mycologically and 43 completely cured onychomycosis patients compared recurrence rates following
treatment with intermittent itraconazole, pulsed itraconazole, continuous terbinafine, and combination terbinafine/itraconazole. Although itraconazole was associated
with higher recurrence rates, no statistically significant differences were detected.13