The Canesten thrush duo contains an oral capsule and tube of external cream that work together to fight thrush at the source of infection. Thrush is a common yeast infection that many people experience at some point in their lives, especially women. Symptoms include itching, irritation, a burning sensation when you go to the loo or unusual vaginal discharge. The active ingredient in Canesten oral capsule is fluconazole, an anti-fungal that works to restore the balance of good and bad bacteria in your body and fight against the fungi or yeast that may be causing your thrush.