Hyaluronic Acid in the Treatment of Hyposalivation

The goal of this clinical trial is to learn if drug containing non-crosslinked hyaluronic acid and amino acids solution (Sunecos-200) works to treat hyposalivation in adults. It will also learn about the safety of drug Sunecos-200. The main questions it aims to answer are: * Does Sunecos-200 improve the saliva secretion and improve a life comfort? * What medical problems do participants have when taking Sunecos-200? Researchers will compare drug containing non-crosslinked hyaluronic acid and amino acids solution (Sunecos-200) to a control group (without intervention) to see if drug Sunecos-200 works to treat hyposalivation. Participants will: * Take drug Sunecos-200 by into oral mucosa injection or nothing every two weeks for 4 times. * Visit the clinic once every 2 weeks for checkups and tests * Keep a diary of their symptoms after injection and fill out a primary and final questionary.