People with primary syphilis can usually be cured with a single injection of a long-acting penicillin. People in later stages require longer treatment with penicillin. Other antibiotics, including doxycycline, azithromycin or ceftriaxone may be effective for people who are allergic to penicillin. All sex partners of people with syphilis should be treated as well. Babies born with congenital syphilis should be treated with a course of penicillin.