First time writer.My husband has just completed his first week of twice a day radiation and once a week chemo. this will last 6 weeks. He has a stage 3 cancer on the back of his tongue and tonsil. He has been given Diflucan for thrush and something for the constipation, Is this a common side effect to either the radiation or the chemo, or both. How long does it take for the Diflucan to take effect.? This thrush is making it difficult for him to eat.