Concerning men, using oral diflucan, for a yeast infection on the tip of the penis, can bring about a cure in about 8 days. If a single dose does not completely relieve symptoms, or the infection is severe, diflucan can be prescribed as three consecutive doses given three days apart. Fluconazole Diflucan Basics Side Effects Reviews Should i be seeing an infectious disease dr at this point? How soon does diflucan take effect . Universal images group editorial/universal images group/getty images. Some side effects may occur due to taking diflucan, however. Fluconazole, sold and marketed by pfizer, is an oral antifungal medication that treats vaginal yeast infections. For mild, uncomplicated, infections fluconazole is prescribed as a single 150 mg dose and an improvement in symptoms is usually seen within one to three days. So how long does diflucan stay in your system? Your doctor will measure blood levels of. Sometimes, the otc creams can help with vaginal itching ...