Is pretreatment confirmation of onychomycosis before prescribing oral terbinafine therapy no longer necessary? Mikailov and colleagues' thought-provoking analysis certainly supports this conclusion, with some important caveats.
Terbinafine, while highly effective against dermatophyte infections, will not clear onychomycosis caused by a yeast or saprophyte; oral azoles such as itraconazole would be the appropriate treatment in such cases, which are best differentiated from dermatophytes through fungal culture. Patients at greater risk for terbinafine-induced hepatotoxicity (eg, history of hepatitis, alcohol consumption, taking potentially hepatotoxic medications such as statins) may also benefit from confirmatory testing prior to starting terbinafine; Mikailov and colleagues' cost analysis does not "carve out" this higher-risk subset. Nevertheless, the risk for clinically apparent liver injury from oral terbinafine has been greatly exaggerated and occurs in as few as 1 in 50,000 to 100,000 treatments, with even rarer instances of durable clinical sequelae.
One thing seems clear though: As long as topical antifungal agents such as efinaconazole remain astronomically expensive, there will still be a cost-saving role for confirmatory testing to "nail down" the diagnosis of onychomycosis first.
Medscape Dermatology © 2016 WebMD, LLC
Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: Is Testing Needed Before Treating Onychomycosis With Terbinafine? - Medscape - Apr 19, 2016.