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Where is the syphilis shot given?

Syphilis is a sexually transmitted infection that is caused by the bacteria Treponema pallidum. If left untreated, syphilis can cause serious health problems. The syphilis bacteria is passed from person to person through direct contact with a syphilis sore, known as a chancre. These sores can occur on or around the genital area, mouth, or anus. Syphilis can also be transmitted from an infected mother to her baby during pregnancy.

How is syphilis treated?

Syphilis is treated through the use of antibiotics, usually penicillin. For early stage syphilis, a single dose of penicillin is often given as a shot in the buttock muscle. This is referred to as the syphilis shot. Giving the antibiotic via intramuscular injection ensures that the full dose is absorbed quickly into the body. Oral antibiotics may be used as an alternative in some cases. For late stage syphilis, multiple doses of penicillin over a longer period of time are usually required to cure the infection.

Why give the syphilis shot in the buttock?

There are a few key reasons the syphilis shot is often administered intramuscularly in the upper outer quadrant of the buttock:

  • The buttock contains a large muscle mass with few major blood vessels and nerves. This makes it a suitable and safe site for injections.
  • The medication can be effectively absorbed from the muscle tissue.
  • Injecting into the buttock allows the use of longer needles to deliver medication deeply into the muscle. This ensures the medication reaches the muscle rather than just underneath the skin.
  • The buttock area provides a degree of privacy for the patient receiving the injection.

Injecting into the buttock muscle allows for quick absorption and action of the penicillin while minimizing pain and injury risk. The upper outer quadrant of the buttock avoids hitting the major sciatic nerve that runs through the lower buttock area.

Are there other injection sites for syphilis treatment?

While the buttock is the most common site, the penicillin injection for syphilis can be administered intramuscularly into other sites as well, including:

  • Deltoid muscle in the upper arm
  • Vastus lateralis muscle in the thigh
  • Ventrogluteal site in the hip

The location may be based on patient comfort, accessibility of the muscle, and volume of medication to be injected. The deltoid can only accommodate a small volume of fluid. The ventrogluteal area may be used for patients who have to lie on their buttocks frequently. The thigh allows easy access but may be less discreet.

Who gives the syphilis shot?

The intramuscular penicillin injection for syphilis is typically given by a doctor, nurse, or other trained healthcare provider. Some common providers who administer the syphilis shot include:

  • Primary care physician
  • Nurse practitioner at a clinic
  • Physician assistant
  • Registered nurse
  • Public health nurse

Many public health departments have STD clinics where patients can receive testing for syphilis. If tested positive, the clinic can provide the penicillin injection onsite as part of the treatment plan.

Where can you get the syphilis shot?

The syphilis shot is often given at the following types of healthcare facilities:

  • Primary care doctor’s office
  • STD clinic or other public health clinic
  • Urgent care center
  • Hospital or emergency room
  • College health center

After being diagnosed with syphilis, discuss treatment options with your healthcare provider. They can advise on the best place to receive the penicillin injection based on your specific situation.

What happens when you get the shot?

Receiving the penicillin shot for syphilis involves the following process:

  1. A healthcare provider will clean the injection site, usually the upper outer quadrant of the buttock, with an antiseptic wipe.
  2. The penicillin solution will be drawn up into a syringe.
  3. A longer intramuscular needle will be used for injection into the buttock muscle.
  4. The provider will inject the medication. Patients may feel a pinch or stinging sensation as the needle goes in.
  5. Pressure will be applied to the site briefly after withdrawing the needle.
  6. A bandage may be applied.
  7. Patients should massage the injection site to help distribute the medication.
  8. Discard instructions will be provided for the syringe and needle.

The whole injection process typically only takes a few minutes. Though the injection itself may be slightly uncomfortable, the penicillin quickly treats the syphilis infection.

What to expect after the syphilis shot

After receiving the intramuscular penicillin injection, patients may experience:

  • Mild soreness, bruising, or redness at the injection site that resolves in a few days
  • Potential temporary numbness near the injection site
  • Slight fever
  • Nausea or vomiting in some cases

Use of warm compresses and over-the-counter pain medication can provide relief. Call a healthcare provider if symptoms worsen or persist beyond a couple days.

Are there alternatives to penicillin for syphilis?

For patients with a penicillin allergy, other types of antibiotics may be used to treat syphilis. Some alternatives include:

  • Doxycycline
  • Tetracycline
  • Ceftriaxone
  • Azithromycin

These medications can be given orally rather than as injections. However, non-penicillin regimens may require longer treatment durations. It’s important to discuss antibiotic options with your healthcare provider if you have a penicillin allergy and contract syphilis.

How effective is the syphilis shot?

When administered properly, a single dose of penicillin is highly effective at curing early stage syphilis. This is why it has long been the preferred treatment method.

According to the Centers for Disease Control (CDC), a single intramuscular injection of penicillin successfully treats primary, secondary, and early latent syphilis in >90% of cases. The syphilis shot generally avoids the issue of patients failing to comply with taking oral medications.

Treating syphilis in the early stages is key because the infection becomes more difficult to cure as it progresses. While the syphilis shot reliably cures early infections, multiple doses over a longer period are required for late stage syphilis.

Why is penicillin the recommended treatment?

Penicillin is considered the gold standard for treating syphilis. Reasons it’s the number one recommended treatment include:

  • High efficacy – It reliably cures early stage syphilis with one injection in nearly all patients
  • Narrow spectrum – Penicillin only targets the syphilis bacteria while sparing normal helpful bacteria
  • Accessibility – Penicillin is widely available and affordable
  • Safety – Used properly, penicillin has a low risk of adverse reactions or side effects

Alternative antibiotics are available but may require longer treatment, have more side effects, or fail more often. This makes penicillin injection the first choice unless a severe allergy is present.

What happens if syphilis is left untreated?

If syphilis is left untreated, it can progress through multiple stages with worsening complications:

Primary stage

A painless sore will develop at the infection site 2-6 weeks after contact with syphilis. It will heal in 2-6 weeks even without treatment. However, the disease remains and can continue to the next stage.

Secondary stage

Rough, reddish-brown rashes will appear on the skin, along with lesions in the mouth, vagina, or anus. Other symptoms like fever, sore throat, and fatigue may occur. Without treatment, it will progress after a few weeks.

Latent stages

Early latent syphilis occurs when there are no more visible symptoms. Late latent syphilis follows a year or more after infection. The bacteria remain in the body during latency and can lead to tertiary syphilis.

Tertiary stage

After 10-30 years, syphilis bacteria can damage organs, nerves, eyes, brain, heart, and cause paralysis. This late stage syphilis is difficult to treat and can be fatal.

That’s why prompt antibiotic treatment like the syphilis shot during early syphilis is crucial. Ongoing screening and public health initiatives to promote awareness and testing help control syphilis spread and enable early treatment.


Syphilis is a prevalent sexually transmitted bacterial infection, but it is highly treatable, especially in its early stages. Typically a single dose of intramuscular penicillin, called the syphilis shot, can reliably cure a syphilis infection when delivered early on. This injection is most often given in the buttock muscle by healthcare personnel at clinics, doctors’ offices, or STD treatment facilities. While uncomfortable briefly, the syphilis shot quickly resolves the infection. When diagnosed with syphilis, immediate treatment with penicillin or alternative antibiotics is critically important to avoid severe complications or transmission to others.