Doxycycline is a broad-spectrum antibiotic commonly used to treat bacterial infections such as respiratory tract infections, urinary tract infections, skin infections, acne, sexually transmitted infections (STIs), and certain types of malaria. It belongs to the tetracycline class of antibiotics and works by inhibiting bacterial protein synthesis. Doxycycline is usually taken orally and is available in various formulations, including tablets, capsules, and suspensions.