Demeclocycline is a tetracycline antibiotic that inhibits bacterial protein synthesis, preventing bacterial growth. It is used primarily to treat bacterial infections caused by susceptible strains, particularly in the respiratory tract, urinary tract, and skin. It is also employed in the management of acne and chronic gingivitis due to its anti-inflammatory properties. Another notable use is in the treatment of syndrome of inappropriate antidiuretic hormone secretion (SIADH), where it induces nephrogenic diabetes insipidus by reducing the kidney's responsiveness to antidiuretic hormone, thus helping to correct hyponatremia when fluid restriction is ineffective.