Demeclocycline hydrochloride is primarily used as an antibiotic to treat various bacterial infections. It is effective against a range of gram-positive and gram-negative bacteria, making it suitable for treating respiratory tract infections, urinary tract infections, and skin infections. Additionally, it is often prescribed for the treatment of acne due to its ability to reduce inflammation and control bacterial growth. Beyond its antibiotic properties, demeclocycline hydrochloride is also used in the management of syndrome of inappropriate antidiuretic hormone secretion (SIADH). It works by inducing nephrogenic diabetes insipidus, which helps to correct the electrolyte imbalance caused by excessive water retention. This application is particularly valuable in clinical settings where fluid regulation is critical. In veterinary medicine, it is sometimes employed to treat infections in animals, particularly in livestock, to ensure their health and productivity. Its broad-spectrum antibacterial activity makes it a versatile option in both human and animal healthcare. However, its use is often limited due to potential side effects, such as photosensitivity and gastrointestinal disturbances, and the availability of newer antibiotics with fewer adverse effects.