Formost 400 Inhaler is used in the treatment of asthma (wheezing and shortness of breath) and chronic obstructive pulmonary disorder (a lung disorder in which the flow of air to the lungs is blocked). It relaxes the muscles of the air passages and making it easier to breathe. Your doctor will tell you how often you need to use your inhaler. The effect of this medicine may be noticeable after a few days but will only reach its maximum after a few weeks. This medicine must be used regularly to be effective, so go on taking it even if you don't have any symptoms. That means it’s doing its job. If you stop taking it your asthma and COPD may get worse. It should not be used to relieve sudden asthma attacks. If an asthma attack occurs, use your quick-relief inhaler (reliever). To get the benefit from this medicine you need to make sure you get your inhaler technique right, otherwise, it Does not work as well.The most common side effects are nausea, vomiting, respiratory tract infection, fungal infections in the mouth, dry mouth, headache, hoarseness of voice, sore throat, cough, musculoskeletal (bone, muscle, or joint) pain, and increased heart rate. If you get there, don’t stop taking it but do talk to your doctor. You can help prevent some of these symptoms by rinsing your mouth and throat with water or brushing your teeth after using your inhaler. There are other, rarer side effects which can be serious. Talk to your doctor if you're worried about them. In general, you should be trying to avoid situations that make your asthma worse (your triggers) and try not to smoke.Ask your doctor whether it’s safe to take this medicine if you're pregnant or breastfeeding. Before taking it, you should tell your doctor if you have any kidney or liver diseases so that your doctor can prescribe a suitable dose for you.