Have you had any experience using itraconazole pulse therapy for ringworm?
A New Zealand shelter veterinarian is interested in experimenting with pulse therapy for dermatophytosis. Dr. Dines recommends instead daily treatment with itraconazole plus weekly topical application of an antifungal product.
I am a shelter vet and recently tried to track down a reference in Plumb for itraconazole pulse therapy for ringworm (5mg/kg SID week 1, 3, 5 with weeks 2 and 4 off treatment). The regimen is referenced to a UK veterinary product, itrafungol, and I have been in contact with the company but have not yet been able to find any research into this protocol. The only paper I have managed to find in the literature using pulse therapy gave itraconazole for 28 days continuously followed by pulse therapy. If I can find any reasonable evidence to support the pulse therapy I would be keen to do a trial with pulse versus continuous therapy in our shelter. I just wanted to know if you have come across this previously and had any experience using this protocol.
As I am sure you are aware, there are numerous treatment protocols that have been attempted for the treatment of dermatophytosis. At this time, some previously described treatments are no longer considered safe or effective (i.e. the use of griseofulvin), while some other protocols leave us without clear answers.
To answer your question briefly, we currently do not recommend pulse therapy with itraconazole for most shelter applications. Even in a private home setting, we tend to stick with our standard protocol.
Currently, what we define as the "gold standard" of treatment would be daily treatment with itraconazole at 5-10 mg/kg for 21 days, along with twice weekly topical application of an antifungal product. We prefer lime sulfur solution at an 8 oz/gallon concentration, but it's my understanding that this is not currently available in your part of the world, so enilconazole is what is most commonly recommended. In shelters that regularly use our protocol we find that it is very rare for a cat to need a second course of itraconazole. Even if they have not cleared their infections completely, they have usually cleared enough for a week or two of topical alone to finish the job.
Pulse therapy requires a loading dose of at least 14 days and so ultimately does not reduce the amount of drug used in treatment, since our protocol calls for only a 21-day course. In addition, we feel like it complicates the treatment schedule enough that many shelters may end up missing doses.
We do recommend using weekly cultures to verify cure. A Wood's lamp may also help you identify areas of the coat that are not getting adequate topical treatment.
Monitoring response to treatment involves monitoring weekly fungal cultures that are kept and examined for 21 days. We expect to see the number of fungal colonies decrease with treatment (p-score). We define a cure as having 2 weeks in a row with negative cultures. The first weekly negative culture can be deemed negative on the 21st day without growth, while the second negative can be assessed on the 14th day and deemed negative if there is no growth.
If you have not already watched them, there are webinars on ASPCAPro.org presented by UW program director Dr. Sandra Newbury that are a great resource for information about ringworm treatment and diagnosis: https://www.aspcapro.org/webinar-series-beating-ringworm.
I hope this has helped to answer your questions. Please let me know if we can be of further assistance.
Brenda Dines, DVM
Maddie’s Shelter Medicine Resident
Shelter Medicine Program
University of Wisconsin – School of Veterinary Medicine