Doxfyn A 400mg/30mg Tablet is used to treat asthma and chronic obstructive pulmonary disorder (a lung disorder in which the flow of air to the lungs is blocked). It helps in relaxing the muscles of the air passages and making it easier to breathe. Doxfyn A 400mg/30mg Tablet also thins and loosens mucus in the nose, windpipe, and lungs making it easier to cough out. It is taken with or without food in a dose and duration as advised by the doctor. The dose you are given will depend on your condition and how you respond to the medicine. You should keep taking this medicine for as long as your doctor recommends. If you stop treatment too early your symptoms may come back and your condition may worsen. Let your healthcare team know about all other medications you are taking as some may affect, or be affected by this medicine. The most common side effects are nausea, stomach upset, vomiting, stomach pain, headache, irritability, insomnia, and increased heart rate. Most of these are temporary and usually resolve with time. Contact your doctor straight away if you are at all concerned about any of these side effects. 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. You should also tell your doctor if you are pregnant, planning pregnancy or breastfeeding.