If you are having trouble with dry mouth you should talk to your doctor about possible causes and treatments. It's important to have enough saliva, so if home remedies and such are not working, get medical care for the problem. If you are taking a medication that causes dry mouth, talk to your doctor about alternatives. There may be another medication for your condition that won't cause the side effect of dry mouth. There are hundreds of medications that are known to cause dry mouth, including very common ones like benadryl, acetaminophen and claritin. In many cases, dry mouth that is serious enough to get medical care is related to a medical issue. It could be the side effect of medical treatment or caused by a medical problem. If your saliva production is especially low, your doctor may prescribe a medication that will increase it. There are several drugs that the doctor may prescribe, depending on your symptoms and any underlying health problems.  Salagen is commonly prescribed to help with low saliva production. Evoxac is a medication that is used to increase saliva production for those that have Sjögren's syndrome, which is a disease that causes dry eyes, mouth, and skin.

TL;DR in Vietnamese:
Trao đổi với bác sĩ về những vấn đề đang xảy ra. Tránh các loại thuốc gây khô miệng. Xử lý các vấn đề tiềm ẩn về sức khỏe. Uống loại thuốc có tác dụng tăng tiết nước bọt.