Oxytetracycline works by interfering with the ability of bacteria to produce proteins that are essential to them. Without these proteins the bacteria cannot grow, multiply and increase in numbers. Oxytetracycline therefore stops the spread of the infection and the remaining bacteria are killed by the immune system or eventually die.

Oxytetracycline is a broad spectrum antibiotic that is active against a wide variety of bacteria. However, some strains of bacteria have developed resistance to this antibiotic, which has reduced its effectiveness for treating some types of infection.

Oxytetracycline may also be used to treat other rarer infections, such as those caused by a group of micro-organisms called rickettsiae (e.g. Q fever). To make sure the bacteria causing an infection are susceptible to oxytetracycline a tissue sample is usually taken, for example a swab from the infected area, or a urine or blood sample.