Oct 1, 1999 Parenteral penicillin continues to be the drug of choice for treatment of all stages of syphilis. Drug Treatment of Common STDs: Part I. Herpes, Syphilis, Urethritis, Chlamydia and Gonorrhea . Trimethoprim/sulfamethoxazole (Bactrim, Septra) . It can present as primary, secondary or...