Onychomycosis is a very common condition leading patients to seek advice from their primary care clinician.
Systemic treatment is the most effective: oral terbenifine is off patent and very inexpensive ($4 per month at Walmart). Its cure rate is 76%. I recommend sending a nail clipping for PAS stain if there is any doubt of the diagnosis. Education about the length of treatment is important. There is a chance of hepatotoxicity, and a few drug interactions to keep in mind as well.
For topical treatment, Vicks VapoRub® has a cure rate of 30% in this FP residency study: http://www.ncbi.nlm.nih.gov/pubmed/21209346
There was visual improvement in the nails in 70% of patients.
For comparison, this study of ciclopirox nail lacquer (http://www.ncbi.nlm.nih.gov/pubmed/11051136) also shows a 30% cure rate.
Vicks VaboRub® is much cheaper (and over the counter) compared to ciclopirox. I recommend Vicks VapoRub® when you and your patient decide topical treatment is the best option.
Robert Moore, MD, MPH