Doxacil® 100 mg is a broad-spectrum antibiotic containing Doxycycline Hydrochloride, a semi-synthetic derivative of oxytetracycline. It is effective against a wide range of bacteria, including Gram-positive and Gram-negative organisms, spirochetes, mycoplasma, rickettsia, and certain mycobacteria. Doxacil® works by inhibiting bacterial protein synthesis, thereby stopping bacterial growth.