Placebo cure rates in the treatment of onychomycosis

Cure Rates of Control Interventions in Randomized Trials for Onychomycosis Treatments: A Systematic Review and Meta-Analysis

Background: The efficacy of antifungals for onychomycosis has been determined in randomized controlled trials (RCTs); interestingly their control arms have demonstrated some therapeutic effects. These controls constitute either placebos (inert pills) or vehicles (all but the antifungal component of the creams). The objective of this research was to determine (i) whether RCT controls exhibited statistically-relevant efficacy rates (i.e. beyond the "placebo effect"), (ii) whether oral and topical controls differed in their efficacies, and (iii) if the efficacy rates of the controls correlated with those of the active comparator associated with that control.

Methods: RCTs of oral and topical monotherapies for dermatophyte toenail onychomycosis were identified through a systematic literature search. For our meta-analyses of cure rates the double arcsine transformation was used. The N-1 chi squared test was used to determine whether the cure rates significantly differed between topical and oral controls. Correlation was investigated using Kendall rank correlation tests.

Results: The pooled mycological, complete, and clinical cure rates of all control interventions (n = 19 trials) were 9%, 1%, and 6%, respectively. The pooled efficacy rates for oral and topical controls were: mycological cure rate, 7% and 12% (p=0.0016); complete cure rate, 1% for both; and clinical cure rate, 4% and 8%, respectively (p=0.0033). For oral RCTs, the respective cure rates of the active therapies were not correlated with controls. However, for topical RCTs, as the mycological and clinical cure rates of the active therapy increased, so did those of the topical vehicle associated with the active therapy in question, and vice versa.

Conclusions: The topical vehicle cure rates were often higher than the oral placebo cure rates, likely due to the presence of non-antifungal chemicals (e.g. moisturizers, urea) with antifungal and debriding properties, which are not present in oral controls.

.

Methyl aminolevulinate photodynamic therapy for onychomycosis: a multicentre, randomized, controlled clinical trial

BACKGROUND

Onychomycosis is a common fungal nail infection that responds poorly to antifungals.

OBJECTIVE

To investigate the efficacy and safety of methyl aminolevulinate (MAL) photodynamic therapy (PDT) in the treatment of onychomycosis.

METHODS

A multicentre (3), randomized, placebo-controlled clinical trial compared the effects of three sessions of urea (40%) plus conventional MAL-PDT with urea (40%) plus placebo (red light) photodynamic therapy (pPDT) in onychomycosis patients. Efficacy, both clinical (onychomycosis severity index, OSI) and microbiological, was blindly evaluated after 36 weeks of follow-up.

RESULTS

Forty patients were analysed in the trial. Twenty-two received MAL-PDT and 18 pPDT. A complete response (OSI = 0) was observed for four patients (18.18%) in the MAL-PDT group and one (5.56%) in the pPDT group (NTT 7.92, 95% CI: 2.98-9.69, P = 0.23). A decrease in OSI score of over 75% (OSI75) was achieved by 40.91% of the patients in the MAL-PDT group and 16.67% in the pPDT group (P = 0.096). Microbiological cure was achieved by seven patients (31.82%) in the MAL-PDT group and two (11.11%) in the pPDT group (P = 0.178). MAL-PDT resulted in better rates of clinical response [OSI >75%: 53.85% vs. 18.75% (P =0.048)] and microbiological cure [41.56% vs. 7.14% (P = 0.037)] in non-dystrophic vs. dystrophic onychomycosis patients. No significant side-effects were reported. The limitations of the study were the reduced sample size and the unexpected efficacy of the control treatment, which was attributed to the 40% urea pre-treatment.

CONCLUSION

This study did not show significant differences between urea 40% + MAL-PDT and urea 40% + pPDT in the treatment of onychomycosis. However, some results suggest that this treatment may constitute an alternative for dermatophyte and non-dermatophyte mould onychomycosis in patients not eligible for systemic treatment, particularly in the absence of total nail dystrophy.