The discoloration probably indicates there is still fungus present. Only a culture of the nail will positively determine if this is so. I would recommend that you talk to your doctor about taking one of the newer oral antifungals for a 90-day period to complete your treatment.
Grisactin is a brand name for griseofulvin, an oral anti-fungal. Griseofulvin was the first oral antifungal drug to be marketed to the public. It has the most limited spectrum antifungal activity of all available oral antifungal drugs. Griseofulvin is a fungistatic drug that slows or stops the growth of the fungus but does not kill it. It is hoped that the body’s defenses can then destroy the weakened fungus. There is a very high recurrence rate after this drug has been discontinued. (I have read studies quoting a 90% reinfection rate.) Because it is necessary to take this drug over a long period of time, and because of the very low cure rates—10%-50% at best without nail removal—this drug is currently used by very few doctors for the treatment of fungal nails.
Today we have newer oral antifungal agents that are showing much more promise for curing onychomycosis (fungal infection of the nail). Terbinafine (Lamisil, manufactured by Novartis) and itraconazole (Sporanox, manufactured by Janssen) are the main oral antifungal drugs now being used by doctors for onychomycosis. Terbinafine is fungicidal (it actually kills the fungus) while itraconazole is fungistatic. Both of these drugs quickly enter the nail bed and are diffused into the entire nail plate rapidly where they accumulate. The rapid buildup of the drug creates a “reservoir effect” helping to produce long-term antifungal action. These agents have been found in nail clippings for period up to 6-9 months after discontinuing therapy. Both of these drugs have a very broad spectrum of activity against fungi, candida, and some of the other organisms commonly found in infections of the nails. Both of these drugs are taken over a three-month period. Of these two antifungal drugs, terbinafine seems to be becoming the drug of choice among podiatrists for the treatment of onychomycosis. -- Dr. Mix