Early syphilis (primary, secondary or early latent syphilis)
Benzathine penicillin G, 2.4 million U IM one time
In penicillin-allergic patients: doxycycline, 100 mg orally twice daily for 2 weeks, or tetracycline, 500 mg orally 4 times daily for 2 weeks. Less effective is erythromycin, 500 mg orally 4 times daily for 2 weeks, or, possibly, ceftriaxone (Rocephin), 1 g IM once daily for 8 to 10 days. (Single-dose ceftriaxone is not effective in the treatment of syphilis.)
Syphilis of more than 1-year duration (late latent or tertiary syphilis without neurologic involvement)
Benzathine penicillin G, 2.4 million U IM weekly for 3 successive weeks
In penicillin-allergic patients: doxycycline, 100 mg orally twice daily for 4 weeks, or tetracycline, 500 mg orally 4 times daily for 4 successive weeks
Neurosyphilis (meningitis, cranial nerve involvement, etc.)*
Aqueous crystalline penicillin G, 12 to 24 million U IV daily (2 to 4 million units every 4 hours) for 10 to 14 days, followed by benzathine penicillin G, 2.4 million U IM weekly for 3 successive weeks
	or
Procaine penicillin G, 2.4 million U IM daily for 10 to 14 days, plus probenecid (Benemid), 500 mg orally 4 times daily for 10 to 14 days, followed by benzathine penicillin G, 2.4 million U IM weekly for 3 successive weeks