Please tell me what can be done for an extremely dry mouth?

Firstly, cause: Determine the cause. Drug, hormonal, age, diet, or pathology related? You will need the help of your physician. Are you well hydrated? After all appropriate tests are completed and causes ruled out, there are salivary substitutes that can be used to help keep your mouth lubricated.

Dry mouth: Some medications as well as certain medical conditions cause dry mouth. Are you hydrating yourself with sufficient water intake during the day? Do you have a high salt diet? Reduced saliva can lead to an increase risk of tooth decay and periodontal disease. Check with your physician as well as your dentist. For patients with chronic dry mouth, use one of the many biotene products designed for this.