 The first @-@ choice treatment for uncomplicated syphilis remains a single dose of intramuscular benzathine penicillin G. Doxycycline and tetracycline are alternative choices for those allergic to penicillin ; due to the risk of birth defects these are not recommended for pregnant women . Resistance to macrolides , rifampin , and clindamycin is often present . Ceftriaxone , a third @-@ generation cephalosporin antibiotic , may be as effective as penicillin @-@ based treatment . It is recommended that a treated person avoid sex until the sores are healed . 
