| Syphilis | Possible therapeutic alternatives | 
| Syphilis (early) Less than one year. Primary: ulcer or chancre at site of infection. Secondary: rash, mucocutaneous lesions, adenopathy.
 | T. pallidum | 
| Benzathine Penicillin G   2.4mu IM x 1 (if pregnant-repeat therapy after 1 week). |  
| Alternatives: |  
| Ceftriaxone 1 gram IV/IM q24h x 10 - 14 days OR |  
| Doxycycline 100mg twice daily for 2 weeks  OR |  
| Azithromycin  2000mg x 1  OR |  
| Tetracycline 500mg four times daily for 2 weeks |  | 
| Syphilis (late, or greater than one year duration) Tertiary (late): cardiac, neurologic, ophthalmic, auditory or gummatous lesions. | T. pallidum | 
| Benzathine Penicillin G 2.4 million units IM weekly x 3 doses |  
| Penicillin allergic patients |  
| Doxycycline 100mg twice daily for 28 days or
 tetracycline 500mg orally four times daily for 28 days.
 |  | 
| Neurosyphilis | T. pallidum | 
| Penicillin G  3 to 4 million units q4h IV for 10-14 days or |  
| Procaine penicillin 2.4 million units IM qd, +  probenecid 500 mg PO qid x 10-14 days |  
| Ampicillin 4 grams IVPB every 6 hours for 10 to 14 days. // Desensitize penicillin allergic patients. |  |