In 2015 they came out with a new treatment for Fistulas that appears to really work, and often better than Cyclosporine. The new product is called :

Tacrolimus Ointment

IF YOUR PUP IS STRUGGLING WITH FISTULAS…..PLEASE TALK TO YOUR VET ABOUT THE POSSIBILITY OF TRYING TACROLIMUS OINTMENT

http://veterinarymedicine.dvm360.com/vin-clinical-qa-how-useful-topical-tacrolimus-treating-perianal-fistulas

At The University of Tennessee, we have had good success treating perianal fistulas with topical tacrolimus (Protopic 0.1%—Fujisawa Healthcare) applied twice a day until the lesions resolve, then tapered to the lowest frequency that controls the inflammation (usually every two or three days).¹Tacrolimus is a macrolide immunosuppressant that inhibits T-lymphocyte activation. It penetrates the skin better than topical cyclosporine does.²

1. A 5-year-old, spayed female German shepherd with severe perianal fistulas.

Tacrolimus costs about $70 for a 30-g tube, so sticker shock can be a problem. Since only enough ointment is needed to cover the lesions, the 30-g tube usually lasts one to three months. Owners should use a cotton-tipped applicator or gloves to avoid contacting the ointment. In people with atopic dermatitis, a mild burning sensation has been reported; however, the patients I have treated for perianal fistulas have not demonstrated any adverse reactions. 

2. The same dog as in Figure 1 after immunosuppressive systemic and topical treatment. Note the change in normal anal structure and the persistent mild inflammation requiring maintenance topical treatments.

For severe cases, we initially give either high-dose prednisolone or cyclosporine, in combination with topical tacrolimus to control the lesions (Figures 1 & 2). Either prednisolone or cyclosporine works well. Prednisolone (0.75 to 1 mg/lb/day orally for two or three weeks; taper the dose over two or three months) is cheaper than cyclosporine but has more side effects. Owners who give cyclosporine (5 mg/kg/day orally on an empty stomach; taper the dose to every other day after six to eight weeks of therapy or when 80% resolution occurs) are usually pleased despite the higher cost.