What is the primary use of doxycycline?

Doxycycline is primarily used for the treatment of various bacterial infections, including sexually transmitted infections (STIs) such as chlamydia and gonorrhea. It belongs to the tetracycline antibiotic class and works by inhibiting bacterial protein synthesis, thereby stopping the growth of bacteria. This makes it effective in treating a wide range of infections beyond just STIs, including respiratory infections and skin infections.

While doxycycline has uses beyond STIs, such as in the treatment of acne and certain types of pneumonia, its established role in treating STIs is significant due to its effectiveness against the pathogens that cause these infections. This specific action highlights its importance in sexually health practices, particularly in regions where STIs are prevalent. In contrast, the other options specified do not relate directly to doxycycline's primary action or common therapeutic uses.