How Syphilis Is Treated

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Syphilis is a fairly common sexually transmitted infection (STI), affecting more than 120,000 people in the United States each year. The mainstay of treatment is penicillin, but other types of antibiotics may be appropriate as well.

Learn more about syphilis and the potential treatment options your healthcare provider may prescribe if you or your partner becomes infected.

syphilis symptoms
Illustration by Joshua Seong. © Verywell, 2018.

Prescriptions

Syphilis is a sexually transmitted infection caused by a bacteria known as Treponema pallidum. The infection cannot be treated with over-the-counter drugs, home remedies, or traditional medicines. As a bacterial infection, syphilis can only be treated with antibacterial drugs known as antibiotics.

Penicillin G

Penicillin G is the antibiotic of choice in almost all cases. Penicillin G, also known as benzylpenicillin, is used to treat many different types of bacterial infections. It is sometimes called a "peanut butter shot" because of its thick consistency.

The drug is typically delivered by a single intramuscular injection into a large muscle, usually the buttocks. In severe cases, penicillin may be given intravenously (by injection into a vein).

There are different preparations of penicillin G, some of which have different consistencies and/or longer or shorter periods of action. The choice of preparation is important because certain types are better able to access tissues (like the brain and spinal cord) than others.

The choice and duration of treatment are largely based on the stage of the infection, known as the primary, secondary, latent, and tertiary stages. Each progressive stage has different symptoms and may need to be treated differently.

If there is neurosyphilis (syphilis of the brain), ocular syphilis (syphilis of the eyes), or otosyphilis (syphilis of the ear), an oral drug called probenecid is typically added to boost the effects of penicillin G.

In 2021, the Centers for Disease Control and Prevention (CDC) issued updated recommendations on the treatment of syphilis:

Stage   Recommended Dosage
Primary, secondary, or early latent syphilis A single intramuscular injection of penicillin G
Late latent syphilis, latent syphilis of unknown duration, or tertiary syphilis Three separate intramuscular injections of penicillin G given a week apart
Neurosyphilis, ocular syphilis, or otosyphilis Intravenous penicillin G delivered over 10 to 14 days in a hospital
OR
Intramuscular penicillin G given once daily plus oral probenecid taken four times daily, both for 10 to 14 days

For otosyphilis, the steroid drug prednisone may also be added to reduce inflammation in the middle ear and help restore hearing.

Alternatives to Penicillin

Other antibiotics may be used for people with syphilis who are allergic to penicillin. These include the antibiotics ceftriaxone, doxycycline, and tetracycline.

The CDC recommends the following alternative treatment strategies for people with primary or secondary syphilis:

Drug Recommended Dosage
Ceftriaxone 1 gram daily delivered either intramuscularly or intravenously for 10 days
Doxycycline 100 mg taken by mouth twice daily for 14 days
Tetracycline 500 mg taken by mouth four times daily for 14 days

It is important to note that these antibiotics are only recommended to treat primary and secondary syphilis. Moreover, allergy testing should be performed to confirm that the individual does, in fact, have a true penicillin allergy.

In advanced cases of syphilis, in which penicillin G remains the most effective option, a procedure known as drug desensitization may be used to prevent allergy in hypertensive people.

Drug Desensitization for Penicillin

Penicillin desensitization is used to make a person less sensitive to penicillin. It involves exposing the individual to gradually increasing doses of penicillin every 15 to 20 minutes in a hospital. When the optimal dose is reached without triggering an allergic reaction, the treatment can begin.

There are cases where penicillin G is the only option and the benefits of treatment may outweigh the risks. This includes the treatment of congenital syphilis in which the T. pallidum is passed from mother to child during pregnancy.

On the other hand, there is evidence that ceftriaxone may be a viable option for people with neurosyphilis when penicillin G is not an option.

Azithromycin, an antibiotic once commonly used to treat syphilis, is no longer recommended due to increasing rates of drug resistance (in which the bacteria resists the effects of the drug).

Treatment of Sexual Partners

According to the CDC, anyone who has had sexual contact with someone diagnosed with primary, secondary, or early latent syphilis should be notified and treated. Specifically:

  • Any person who has had sex within three months with someone diagnosed with primary syphilis
  • Any person who has had sex within six months with someone diagnosed with secondary syphilis
  • Any person who has had sex within 12 months with someone diagnosed with early latent syphilis

If the sexual contact occurred less than 90 days before the diagnosis, the partner would be treated presumptively. This would be the case even if the partner's syphilis test is negative.

If the sexual contact occurred more than 90 days before the diagnosis, the partner could opt for a syphilis test if they choose. If the test result is negative, no treatment is required.

Surgery and Specialist-Driven Procedures

Surgery is not a common part of the treatment for syphilis, but it may be needed in certain emergency situations.

This includes rare instances in which tertiary syphilis can cause an aortic aneurysm (the potentially deadly bulging of the main artery of the heart) or a highly destructive tumor in the brain known as a cerebral syphilitic gumma.

While surgery is avoided for most syphilitic gummas (mainly because they usually resolve with antibiotics), those in the brain are commonly treated to avoid potentially serious complications, including the loss of mobility and death.

Other gummas may be surgically removed if they are fungating (meaning that they are breaking open and causing tissue death). If left untreated, fungating gummas become infected and lead to sepsis (blood poisoning).

Summary

Penicillin G is the mainstay of treatment for syphilis. Depending on the stage of infection and other factors, the preparation, dose, and duration of therapy can vary. If penicillin G cannot be used due to a penicillin allergy, other antibiotics may be prescribed. The sexual partners of someone with syphilis should also be treated.

Surgery is sometimes needed for people with complications of tertiary syphilis, such as an aortic aneurysm or a brain mass known as a cerebral syphilitic gumma.

A Word From Verywell

Many people with syphilis have no idea that they've been infected. Because of this, the CDC recommends routine screening for people at high risk of infection or disease complications. These include pregnant persons, men who have sex with men (MSM), and people with HIV.

By getting tested, you can seek immediate, effective treatment if the test is positive, protecting yourself and others.

Frequently Asked Questions

  • How is syphilis treated?

    An intramuscular injection of penicillin G is the preferred treatment. Generally, a single shot of long-acting benzathine penicillin G will cure a person of primary, secondary, or early latent syphilis.

    Late latent and tertiary syphilis are treated with three doses of penicillin G given at one-week intervals.

  • How is syphilis treated if you are allergic to penicillin?

    Even if there is an allergy, penicillin G is still the treatment of choice. Your healthcare provider may do allergy testing to verify if you are at true risk. If penicillin is not an option, other antibiotics may be explored, including ceftriaxone, doxycycline, and tetracycline.

  • How is syphilis treated during pregnancy?

    Penicillin G is the only recommended treatment during pregnancy. Pregnant persons who are allergic to penicillin would need to undergo penicillin desensitization in a hospital.

  • Do sex partners exposed to syphilis always need treatment?

    Yes. If you have had sex with someone within 90 days of their syphilis diagnosis, you would be presumptively treated even if a syphilis test is negative.

  • How long is syphilis contagious after treatment?

    You would need to abstain from sex until the syphilis sores (called chancres) are fully healed. People with vaginas or those who were exposed through anal sex may need a physical exam as the sores may be internal and not readily seen.

  • Why is follow-up testing needed after syphilis treatment?

    Follow-up testing is recommended six to 12 months after the completion of treatment to ensure that it worked. Syphilis antibody levels will be elevated immediately after treatment and will gradually subside over time.

    A four-fold decrease in antibodies after one year is considered a treatment success.

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11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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