oxytetracycline

Oxytetracycline is a broad-spectrum antibiotic in the tetracycline class used to treat a variety of infections in humans and animals. It exerts its effect by reversibly binding to the 30S ribosomal subunit, inhibiting the attachment of aminoacyl-tRNA and thereby bacterial protein synthesis.

It is active against a wide range of Gram-positive and Gram-negative bacteria and atypical pathogens such as Chlamydia, Mycoplasma, and Rickettsia. This makes it useful for respiratory, skin, and certain urinary and sexually transmitted infections, as well as some zoonotic and rickettsial diseases.

Formulations include oral tablets and solutions, injectable forms (oxytetracycline hydrochloride or calcium salts), and topical preparations such as ophthalmic ointments. Absorption by mouth is generally good but reduced by dairy products and antacids due to chelation with divalent cations; it distributes widely in body tissues and fluids, crosses the placenta, and is excreted by the kidneys and bile.

In humans, oxytetracycline is used for acne and rosacea, various respiratory and skin infections, urinary and some sexually transmitted infections, and certain atypical infections. In veterinary medicine, it is widely used for respiratory, enteric, and systemic infections in cattle, horses, pigs, and fish; dosing is species-specific, and regulatory restrictions have limited or banned its use as a growth promoter in many regions.

Safety considerations include nausea, vomiting, diarrhea, and photosensitivity; dental discoloration and enamel hypoplasia can occur in children, and hepatic or renal toxicity is possible in rare cases. It should not be used in pregnancy or in young children, and concomitant calcium-containing products should be avoided at dosing times for oral forms. Resistance can arise via efflux pumps and ribosomal protection proteins, underscoring the importance of prudent use.