Canesten Thrush Combi Internal & External Creams is a complete treatment for vaginal thrush because it treats both the internal cause and external symptoms. Only use this product if you have been previously diagnosed by your doctor as having vaginal thrush. The active substance in Canesten Thrush Combi Internal & External Creams is clotrimazole. Clotrimazole belongs to a group of medicines called azoles and is an antifungal agent which fights the cause of infections such as vaginal thrush.