Antibiotics are drugs available in Project Zomboid for use of the treatment of regular infections which arise from having a open wound not disinfected which then leads to infection. (Not to be confused with Zombification/Zombie Infection, which is always fatal)
Antibiotics half the strength of a current infection to help it heal.
Antibiotics also help with the treatment of colds.
Antibiotics spawn in medical counters in medical facilities. They can spawn at the Cortman Medical or at the Mall as examples.