Hi... Thanks for the query.. As you were taking antibiotics for a long duration, therefore there is a possibility that you have got yeast infection in mouth causing oral thrush that is a common cause of dry mouth especially after antibiotic therapy.. Metallic taste is a side effect of antibiotic intake.. So first of all you should consult an Oral Physician and get checked that whether you have a white coating over the tongue or not. As far as metallic taste is concerned it will gradually resolve on its own.. You should consult an Oral Physician and get evaluated. For now you can start chewing sugarfree chewing gums, use mouth lubricants like Oral Gel, and clean your tongue using a tongue scraper.. You can also continue Biotene.. Hope this helps.. Regards.