Antibiotics are not always used to fight pneumonia - they are effective only in case of bacterial pneumonia. Pneumonia is simply inflammation of the lungs and filling of the alveoli with fluid. The causes of pneumonia can vary - infections can be caused by bacteria, fungi, viruses, parasites, and pneumonia can even be caused by injury to the lungs, either from chemicals or from physical trauma. Obviously, antibiotics are useless in the case of the latter causes, but even in the case of viral and parasitic infections, antibiotics are useless, and can only be harmful. Fungal pneumonia is quite rare, and it too is not treated by using antibiotics, but by using antifungal drugs.
If you do have a bacterial infection that has caused pneumonia, your doctor will prescribe antibiotics as part of the treatment. The duration of the treatment varies, depending on the extent and severity of the infection, as well as the general state of your health. In general however, antibiotic treatment lasts for no longer than a week. Your doctor will be able to give you a more accurate estimate, since he or she will be more aware of the details of your case. I hope that you are not treating yourself - this is extremely dangerous with a disease such as pneumonia. Not only do you run the risk of allowing a viral or other infection to worsen, you also inadvertently create antibiotic resistant bacteria, and may also cause other health complications for yourself.
If you are being treated by a doctor and the antibiotics have no effect even after ten days, you should ask your doctor whether it could be a non-bacterial infection and whether you should test your blood and phlegm to detect the cause. Some doctors do tend to prescribe antibiotics rather indiscriminately, and unless you are really sure that your doctor is competent and responsible, you may do well to get a second opinion.
answered by G M