Tetracycline hydrochloride is a yellow, odorless, crystalline powder. Tetracycline is stable in air but exposure to strong sunlight causes it to darken. Its potency is affected in solutions of pH below 2 and is rapidly destroyed by alkali hydroxide solutions. Tetracycline is very slightly soluble in water, freely soluble in dilute acid and in alkali hydroxide solutions, sparingly soluble in alcohol, and practically insoluble in chloroform and in ether.

Tetracycline hydrochloride is a broad spectrum polyketide antibiotic produced by the Streptomyces genus of Actinobacteria. It exerts a bacteriostatic effect on bacteria by binding reversible to the bacterial 30S ribosomal subunit and blocking incoming aminoacyl tRNA from binding to the ribosome acceptor site. It also binds to some extent to the bacterial 50S ribosomal subunit and may alter the cytoplasmic membrane causing intracellular components to leak from bacterial cells.

Tetracycline hydrochloride is used to treat a wide variety of infections, including acne. It is an antibiotic that works by stopping the growth of bacteria. This antibiotic treats only bacterial infections. It will not work for viral infections (such as common cold, flu). Using any antibiotic when it is not needed can cause it to not work for future infections. Tetracycline can also be used in combination with anti-ulcer medications to treat certain types of stomach ulcers.

Overuse of tetracycline (and other antibiotics) in humans and farm animals have allowed some bacteria to build up a resistance to antibiotics. The development of these so-called "superbug" bacteria limits the number of infections that antibiotics such as tetracycline can treat. Tetracycline is also effective in animals that have tick-borne infections, such as Lyme disease, ehrlichiosis, and Rocky Mountain spotted fever.

Tetracycline is a pregnancy category D drug. Studies show the medication can impair the development of bones in infants. Use during pregnancy can also cause lifelong tooth discoloration in your child. Tetracycline is secreted in breast milk and may affect bone and tooth development in a nursing infant. Women should not use this medication while breastfeeding.