You should not switch from Fomtide 200 to Combitide 250 on your own without medical advice. Though both inhalers are used to control asthma, they contain different medicines and doses. If Fomtide 200 is unavailable, the safest step is to ask your doctor to suggest the closest suitable alternative and correct dose based on your condition. Do not stop or change your inhaler suddenly, as this can worsen your breathing symptoms.