Which antifungal agent for onychomycosis? A pharmacoeconomic analysis

Line-field confocal optical coherence tomography, a novel non-invasive tool for the diagnosis of onychomycosis

BACKGROUND AND OBJECTIVES

Onychomycosis is common and important to distinguish from other nail diseases. Rapid and accurate diagnosis is necessary for optimal patient treatment and outcome. Non-invasive diagnostic tools have increasing potential for nail diseases including onychomycosis. This study evaluated line-field confocal optical coherence tomography (LC-OCT) as a rapid non-invasive tool for diagnosing onychomycosis as compared to confocal laser scanning microscopy (CLSM), optical coherence tomography (OCT), and conventional methods.

PATIENTS AND METHODS

In this prospective study 86 patients with clinically suspected onychomycosis and 14 controls were examined using LC-OCT, OCT, and CLSM. KOH-preparation, fungal culture, PCR, and histopathology were used as comparative conventional methods.

RESULTS

LC-OCT had the highest sensitivity and negative predictive value of all methods used, closely followed by PCR and OCT. Specificity and positive predictive value of LC-OCT were as high as with CLSM, while OCT scored much lower. The gold standard technique, fungal culture, showed the lowest sensitivity and negative predictive value. Only PCR and culture allowed species differentiation.

CONCLUSIONS

LC-OCT enables quick and non-invasive detection of onychomycosis, with advantages over CLSM and OCT, and similar diagnostic accuracy to PCR but lacking species differentiation. For accurate nail examination, LC-OCT requires well-trained and experienced operators.

Konfokale Line-Field optische Kohärenztomographie, ein innovatives nichtinvasives Instrument zur Diagnose der Onychomykose: Line-field confocal optical coherence tomography, a novel non-invasive tool for the diagnosis of onychomycosis

Hintergrund und Ziele

Onychomykose ist weit verbreitet und sollte von anderen Nagelerkrankungen unterschieden werden. Eine rasche und genaue Diagnostik ist für die optimale Behandlung des Patienten und ein bestmögliches Ergebnis erforderlich. Nichtinvasive Techniken haben ein wachsendes Potenzial bei der Diagnose von Nagelerkrankungen, einschließlich Onychomykose. In dieser Studie wurde die konfokale Line‐Field optische Kohärenztomographie (LC‐OCT) als schnelle nichtinvasive Methode zur Diagnose von Onychomykose im Vergleich zur konfokalen Laserscanmikroskopie (KLM), optischen Kohärenztomographie (OCT) und konventionellen Methoden bewertet.

Patienten und Methodik

In dieser prospektiven Studie wurden 86 Patienten mit klinischem Verdacht auf Onychomykose und 14 Kontrollen mittels LC‐OCT, OCT und KLM untersucht. KOH‐Präparation, Pilzkultur, PCR und Histopathologie wurden als vergleichende konventionelle Methoden eingesetzt.

Ergebnisse

LC‐OCT hatte die höchste Sensitivität und den höchsten negativen Vorhersagewert aller verwendeten Methoden, dicht gefolgt von PCR und OCT. Die Spezifität und der positive Vorhersagewert der LC‐OCT waren genauso hoch wie bei der KLM, während OCT deutlich schlechter abschnitt. Das Goldstandardverfahren Pilzkultur zeigte die geringste Sensitivität und den niedrigsten negativen Vorhersagewert. Nur PCR und Kultur ermöglichten eine Differenzierung der Pilzspezies.

Schlussfolgerungen

LC‐OCT ermöglicht eine schnelle und nichtinvasive Diagnostik von Onychomykose, mit Vorteilen gegenüber KLM und OCT und ähnlicher diagnostischer Genauigkeit wie die PCR, aber ohne Differenzierung der Pilzarten. Für eine genaue Nageluntersuchung erfordert die LC‐OCT gut geschulte und erfahrene Anwender.

Controlled-release injectable containing terbinafine/PLGA microspheres for onychomycosis treatment

Controlled-release drug delivery systems based on biodegradable polymers have been extensively evaluated for use in localized drug delivery. In the present study, intralesionally injectable poly (lactide-co-glycolide) (PLGA) microspheres for controlled release of terbinafine hydrochloride (TH) was developed for treating fungal toe/finger nail infections. TH-PLGA microspheres were formulated using O/W emulsification and modified solvent extraction/evaporation technique. Microspheres were evaluated for particle size and size distribution, encapsulation efficiency, surface, and morphology. The in vitro drug release profile was studied in aqueous media as well as in 1% agar gel. Microspheres system was also evaluated in excised cadaver toe model, and extent of TH accumulation in nail bed, nail plate, and nail matrix was measured at different time points. Microspheres were found to provide consistent and sustained TH release. Intralesional administration of controlled-release microspheres can be a potential alternative mode of treating fungus-infected toe and/or finger nails.

Clinical diagnosis of toenail onychomycosis is possible in some patients: cross-sectional diagnostic study and development of a diagnostic rule

BACKGROUND

Suspected toenail onychomycosis is a frequent problem. Clinical diagnosis has been considered inadequate.

OBJECTIVES

To assess the diagnostic accuracy of clinical findings for detecting fungi in toenails, and to develop and validate a clinical diagnostic rule aimed at improving dermatologists' diagnosis of onychomycosis.

METHODS

A cross-sectional diagnostic study was performed including a total of 277 patients seen by 12 dermatologists. The gold standard was the presence of dermatophytes on culture or a positive nail plate biopsy. For each sign we described prevalence, sensitivity, specificity, positive and negative predictive values, and likelihood ratios for positive and negative results. We developed a diagnostic clinical rule and validated it in a subsample.

RESULTS

Helpful findings to predict the presence of fungi are: previous diagnosis of fungal disease; abnormal plantar desquamation (affecting > 25% of the sole); onychomycosis considered the most probable diagnosis by a dermatologist; and presence of interdigital tinea. When dermatologists considered onychomycosis the most probable diagnosis and plantar desquamation was present (13% of patients), the positive predictive value for presence of fungi was 81%. When both signs were absent (34% of patients), the positive predictive value for absence of fungi was 71%. In other situations, clinical diagnosis might not give enough information to decide on therapy.

CONCLUSIONS

In 13% of the patients (a large number in absolute terms), when dermatologists consider onychomycosis the most probable diagnosis and plantar desquamation is present, therapy should be started without any further test, as clinical diagnosis is at least as accurate as laboratory tests. In other situations, an optimal management strategy should be defined.

[Antifungal agents for onychomycoses]

Nail fungal infections are considered one of the major dermatological problems due to their high rate of therapeutic failure, management and treatment difficulties. Long-term treatments, inadequate therapies, mycological misdiagnosis and follow-up, secondary alterations of the nail, and resistant microorganisms, are some of the causes of these complications. Although the discovery of new antifungal agents has provided some effective molecules, none of the current available drugs are totally effective. It is important to continue researching in this field to provide new antifungal agents and combined therapies.

Nondermatophytic filamentous fungi infection in South America--reality or misdiagnosis?

For the last 10 years, a steady increment in the diagnosis of nondermatophyte filamentous fungal infections has been observed. This trend also applies to the valuation of the medical mycology. It can be attributed, in part, to the increased concern of the population with the aesthetic aspect, the easiest access to health information, and the increased demand for specialized jobs. Moreover, increase in the diagnosis of new emerging fungi is also caused by the improvement of the diagnostic techniques available as well as the qualification and constant update of the professionals in medical mycology. Another relevant aspect is the valorization of medical mycology in the medical curriculum. Misdiagnosis can lead to treatment failures, because not all nail diseases are caused by fungi. Therefore, the importance of clinical diagnosis is strictly associated with laboratory results.

The effects of laser irradiation on Trichophyton rubrum growth

The effects of various laser wavelengths and fluences on the fungal isolate, Trichophyton rubrum, were examined in vitro. Standard-size isolates of T. rubrum were irradiated by using various laser systems. Colony areas were compared for growth inhibition on days 1, 3, and 6 after laser irradiation. Statistically significant growth inhibition of T. rubrum was detected in colonies treated with the 1,064-nm Q-switched Nd:YAG laser at 4 and 8 J/cm(2) and 532-nm Q-switched Nd:YAG laser at 8 J/cm(2). Q-switched Nd:YAG laser at 532- and 1,064-nm wavelengths produced significant inhibitory effect upon the fungal isolate T. rubrum in this in vitro study. However, more in vitro and in vivo studies are necessary to investigate if lasers would have a potential use in the treatment of fungal infections of skin and its adnexa.

Pharmacoeconomics--an aid to better decision-making

OBJECTIVES

The first aim of this workshop was to define pharmacoeconomic concepts and terminology. Pharmacoeconomics can be defined as the branch of economics that uses cost-benefit, cost-effectiveness, cost-minimization, cost-of-illness and cost-utility analyses to compare pharmaceutical products and treatment strategies. Economic evaluations provide healthcare decision-makers with valuable information, allowing optimal allocation of limited resources. However, pharmacoeconomics is based on long-term benefits, whereas physicians are typically forced to seek immediate savings. The second aim was to review pharmacoeconomic studies in the field of onychomycosis and finally to discuss future perspectives.

RESULTS AND CONCLUSIONS

We discussed current pharmacoeconomic issues on the management of onychomycosis. Consensus was reached on the following issues: * Published pharmacoeconomic studies concerning onychomycosis are flawed. Future studies should be based on internationally validated principles and appropriate models. The fact that costs of different drugs, laboratory examinations and physician visits vary worldwide should be considered. Cost-benefit studies are required. * The National Institute for Clinical Excellence (NICE) recommendations are often considered in countries other than the UK, even when not adapted to the country in question. * Generic drugs might reduce costs, but this depends on their effectiveness (bioavailability). * Sampling requests affect the economic cost (dependent on methodology, which depends on country) and physicians often trust their instincts even when tests are repeatedly negative. * The cost of adverse event management is usually considered to be 10%; this may be too high for onychomycosis, as treatments are relatively safe without severe side-effects. * Probability of recurrence for each drug should be determined. * Need for disease severity standardization, definition of diagnostic criteria and successful treatment (mycological and clinical cure).

Pulse versus continuous terbinafine for onychomycosis: A randomized, double-blind, controlled trial

BACKGROUND

Effective treatments for onychomycosis are expensive. Previous studies suggest that less costly, pulsed doses of antifungal medications may be as effective as standard, continuous doses. Terbinafine is the current treatment of choice for toenail onychomycosis.

OBJECTIVE

Our purpose was to determine whether pulse-dose terbinafine is as effective as standard continuous-dose terbinafine for treatment of toenail onychomycosis.

METHODS

We conducted a double-blind, randomized, noninferiority, clinical intervention trial in the Minneapolis Veterans Affairs Medical Center. The main inclusion criteria for participants were a positive dermatophyte culture and at least 25% distal subungual clinical involvement. Six hundred eighteen volunteers were screened; 306 were randomized. Terbinafine, 250 mg daily for 3 months (continuous) or terbinafine, 500 mg daily for 1 week per month for 3 months (pulse) was administered. The primary outcome measure was mycological cure of the target toenail at 18 months. Secondary outcome measures included clinical cure and complete (clinical plus mycological) cure of the target toenail and complete cure of all 10 toenails.

RESULTS

Results of an intent-to-treat analysis did not meet the prespecified criterion for noninferiority but did demonstrate the superiority of continuous-dose terbinafine for: mycological cure of the target toenail (70.9% [105/148] vs 58.7% [84/143]; P =.03, relative risk [RR] of 1.21 [95% confidence interval (CI), 1.02-1.43]); clinical cure of the target toenail (44.6% [66/148] vs 29.3% [42/143]; P =.007, RR =1.52 [95% CI, 1.11-2.07); complete cure of the target toenail (40.5% [60/148] vs 28.0% [40/143]; P =.02, RR=1.45 [95% CI, 1.04-2.01); and complete cure of all 10 toenails (25.2% [36/143] vs 14.7% [21/143]; P =.03, RR =1.71 [95% CI, 1.05-2.79). Tolerability of the regimens did not differ significantly between the groups (chi2 =1.63; P =.65).

LIMITATIONS

The study population primarily consisted of older men with severe onychomycosis.

CONCLUSIONS

This study demonstrated the superiority of continuous- over pulse-dose terbinafine. We also found this expensive therapy to be much less effective than previously believed, particularly for achieving complete cure of all 10 toenails.

Treatment options - development of consensus guidelines

BACKGROUND

There are currently three main treatment strategies for onychomycosis: topical, oral and combination. Amorolfine nail lacquer appears to be the most effective form of topical monotherapy. However, the best mycological and clinical cure rates are obtained with combination therapy. Combination therapy increases antifungal spectrum, fungicidal activity and safety. New antifungals (triazoles and echinocandins) were recently developed, enabling new protocols.

OBJECTIVES

To review available therapies. To design an algorithm for the management of onychomycoses in daily practice.

RESULTS

Therapeutic choice should be based on numerous factors including patient's age and health, aetiology, extent of involvement and clinical form. The consensus was that topical monotherapy is recommended when < 50% of the nail is affected without matrix area involvement. Oral monotherapy or combination therapy is indicated when > 50% of the nail, including the matrix area, is involved. Topical treatments should not be used alone when topical drug transport is suboptimal (i.e. when dermatophytoma, onycholysis or spikes are present). Chemical or mechanical removal should also be considered whenever applicable (interruption of drug transport).

CONCLUSION

In conclusion, treatment decision-making tools (e.g. an illustrated booklet or CD-ROM presenting each type of onychomycosis and criteria to be considered before selecting treatment regimen) would be valuable supports for the successful treatment of onychomycoses.

Diabetes mellitus and candidiases

Patients in various clinical states of diabetes mellitus (according to the recommendation of the American Diabetes Association) as a primary diagnosis were examined for fungal infections by Candida species. Candida spp. were detected in urine, in the material taken from the mouth cavity, nails, skin lesions, ears and eyes, by cultivation on the Sabouraud agar, CHROMagar Candida, and by saccharide assimilation. In the group of diabetics with symptoms of oral candidiasis and denture stomatitis C. albicans was identified in 8 cases, C. tropicalis in 3, C. parapsilosis in 2; 1 strain of C. guilliermondii was also isolated. In patients with urinary tract infections the presence of C. albicans was shown in 12 cases; C. parapsilosis was detected in 6 cases and two strains of each C. tropicalis and C. krusei were also isolated. In patients with leg ulcers C. albicans (25 cases), C. parapsilosis (5), C. tropicalis (3) and one strain of each C. krusei and C. robusta were isolated. Otomycosis was associated with one strain of C. albicans, C. parapsilosis, C. tropicalis and C. guilliermondii. C. albicans was most frequently associated with onychomycosis, paronychia and endophthalmitis; C. parapsilosis was the second most rated yeast.

Common Fungal Infections of the Feet in Patients with Diabetes Mellitus

Superficial fungal infections of the foot (tinea pedis and onychomycosis) are common among elderly patients. Although most authorities believe that patients with diabetes mellitus have an increased predisposition to dermatophytic infections, some controversies still remain. Because these infections disrupt the skin integrity and provide an avenue for bacterial superinfection, elderly diabetic patients with dermatophytic infection should be promptly treated with an antifungal agent. For most dermatophytic infections of the foot, topical agents are usually effective and less expensive than oral agents. Laboratory diagnosis of fungal infection prior to institution of therapy is recommended. Proper technique for obtaining the specimen is important to ensure a higher chance of isolating the infecting fungus. Commonly used anti-dermatophytic agents that are also active against the yeasts include the imidazoles, the allylamines-benzylamines and the hydroxypyridones, which are also effective against most of the moulds. Oral therapy for tinea pedis, although not well studied, should be limited to patients with more extensive infections, such as vesicobullous and moccasin type, resistant infections or chronic infections. In addition, oral agents should also be considered in diabetic and immunosuppressed patients. On the other hand, treatment of onychomycosis of the foot usually requires systemic therapy. Griseofulvin is the least effective agent when compared with the newer agents. Terbinafine, itraconazole and fluconazole have been shown to have acceptable cure rates. More recently, topical treatment of the nail with 8% ciclopirox nail lacquer, bifonazole with urea and amorolfine have been reported to be successful. Over the past decade, fungal foot infections of the skin and nail are more effectively treated with the introduction of numerous topical and oral agents.

Terbinafine: a review of its use in onychomycosis in adults

Terbinafine, an orally and topically active antimycotic agent, inhibits the biosynthesis of the principal sterol in fungi, ergosterol, at the level of squalene epoxidase. Squalene epoxidase inhibition results in ergosterol-depleted fungal cell membranes (fungistatic effect) and the toxic accumulation of intracellular squalene (fungicidal effect). Terbinafine has demonstrated excellent fungicidal activity against the dermatophytes and variable activity against yeasts and non-dermatophyte molds in vitro. Following oral administration, terbinafine is rapidly absorbed and widely distributed to body tissues including the poorly perfused nail matrix. Nail terbinafine concentrations are detected within 1 week after starting therapy and persist for at least 30 weeks after the completion of treatment. Randomized, double-blind trials showed oral terbinafine 250 mg/day for 12 or 16 weeks was more efficacious than itraconazole, fluconazole and griseofulvin in dermatophyte onychomycosis of the toenails. In particular, at 72 weeks' follow-up, the multicenter, multinational, L.I.ON. (Lamisil vs Itraconazole in ONychomycosis) study found that mycologic cure rates (76 vs 38% of patients after 12 weeks' treatment; 81 vs 49% of recipients after 16 weeks' therapy) and complete cure rates were approximately twice as high after terbinafine treatment than after itraconazole (3 or 4 cycles of 400 mg/day for 1 week repeated every 4 weeks) in patients with toenail mycosis. Furthermore, the L.I.ON. Icelandic Extension study demonstrated that terbinafine was more clinically effective than intermittent itraconazole to a statistically significant extent at 5-year follow-up. Terbinafine produced a superior complete cure rate (35 vs 14%), mycologic cure rate (46 vs 13%) and clinical cure rate (42 vs 18%) to that of itraconazole. The mycologic and clinical relapse rates were 23% and 21% in the terbinafine group, respectively, compared with 53% and 48% in the itraconazole group. In comparative clinical trials, oral terbinafine had a better tolerability profile than griseofulvin and a comparable profile to that of itraconazole or fluconazole. Post marketing surveillance confirmed terbinafine's good tolerability profile. Adverse events were experienced by 10.5% of terbinafine recipients, with gastrointestinal complaints being the most common. Unlike the azoles, terbinafine has a low potential for drug-drug interactions. Most pharmacoeconomic evaluations have shown that the greater clinical effectiveness of oral terbinafine in dermatophyte onychomycosis translates into a cost-effectiveness ratio superior to that of itraconazole, fluconazole and griseofulvin.

CONCLUSION

Oral terbinafine has demonstrated greater effectiveness than itraconazole, fluconazole and griseofulvin in randomized trials involving patients with onychomycosis caused by dermatophytes. The drug is generally well tolerated and has a low potential for drug interactions. Therefore, terbinafine is the treatment of choice for dermatophyte onychomycosis.