The drug is the go-to treatment for syphilis and the only one recommended for pregnant people. But a shortage of the injectable drug has prompted some public health agencies to ration it.
The shortage comes as there has been a steady increase in rates of syphilis since 2000. Inventory can start depleting as early as this month, Pfizer said.
Syphilis cases are on the rise. The bacterium that causes the sexually transmitted disease is becoming resistant to some antibiotics. But somehow, penicillin has remained the best weapon against it.
The medication is the only one available to prevent an infected pregnant woman from passing the disease to a fetus. Pfizer says the shortage should be over in July.