What medication is used to treat syphilis?

In general, most patients with early-stage syphilis can achieve clinical cure and become non-infectious. Syphilis is a chronic infectious disease caused by the bacterium *Treponema pallidum*, and it spreads primarily through two routes: sexual contact and blood transmission. Once infected, *T. pallidum* can invade various tissues and organs throughout the body. So, what medications are used to treat syphilis? Below, we address this question.

What Medications Are Used to Treat Syphilis?

Commonly prescribed medications for syphilis include penicillin, tetracyclines, erythromycin, and “qing leisu” (a Chinese term historically referring to penicillin or related antibiotics). Penicillin remains the first-line treatment; regimens such as benzathine penicillin G are widely used. Prior to administration, a skin test must be performed to rule out penicillin allergy. Sulfonamide drugs—such as probenecid—are occasionally employed, particularly in cases of neurosyphilis. Following treatment, patients should undergo regular physical examinations, serological testing, and imaging studies to assess therapeutic response. Tetracyclines and macrolides are less effective than penicillin and are generally reserved for patients with penicillin allergy. Commonly used agents in these classes include tetracycline, doxycycline, minocycline, and azithromycin. Notably, doxycycline and azithromycin are contraindicated in pregnant women with syphilis.

Additional Information: Modes of Syphilis Transmission

1. Transmission via Blood Transfusion

If a blood donor has latent syphilis, their blood may contain viable *Treponema pallidum*. Transfusion of such blood into a recipient can result in infection. These recipients typically do not develop primary syphilis manifestations but instead present directly with secondary syphilis symptoms. Therefore, routine serological screening for syphilis in blood donors is critically important.

2. Mother-to-Child (Congenital) Transmission

This occurs when a pregnant woman with untreated syphilis transmits *T. pallidum* across the placenta to her fetus via the placental circulation. The spirochetes present in the mother’s bloodstream can cross into the fetal circulation, resulting in congenital syphilis. Hence, maintaining good health and seeking timely treatment before and during pregnancy is essential to safeguard the health of future generations.

3. Indirect (Fomite-Mediated) Transmission

Sharing personal items—such as undergarments, bedding, towels, razors, bath towels, bathtubs, or toilet fixtures—with a person who has syphilis poses a risk of infection. These objects may harbor *T. pallidum* shed from active lesions. Additionally, rare cases may result from direct skin or mucosal contact with an infected individual.

The above outlines the pharmacologic management of syphilis. We hope this information is helpful to you.