Being Treated with Bicillin L-A for Syphilis
Care instructions
Taking Bicillin L-A
You get Bicillin L-A as an injection (also called a shot). The number of injections you get depends on what stage of syphilis you have. Your nurse or doctor will talk to you about this. Injections are given 1 time a week, and you may need up to 3 rounds of injections.
Who can’t have Bicillin L-A?
Talk to your nurse or doctor before you get this medicine if you’re allergic to or you’ve had a reaction to penicillin, amoxicillin, or a cephalosporin medicine (such as Keflex or Ceclor). This will help your nurse or doctor decide if you can have Bicillin L-A.
Side effects
Bicillin L-A may cause an upset stomach (nausea) and vomiting (throwing up). You may also have pain and tenderness where you get the injection.
After you get the injection, you can have a reaction called a Jarisch-Herxheimer reaction. Symptoms may include:
- chills, fever—temperature over 38.5°C (101.3°F)
- faster heart rate than normal
- muscle and joint pain
- sweating
- feeling tired
- headache
- rash
This reaction can happen 4 to 6 hours after the injection. It usually goes away in 24 hours. You can take pain medicine like acetaminophen (Tylenol). Follow the package directions or talk to your doctor or pharmacist before you take it.
Go to an emergency department or call 911 if you have:
- trouble breathing or swallowing
- swelling or tingling in your mouth or on your face
- hives
- wheezing (a whistling sound when you breathe)
Pregnancy
If you’re pregnant and you have a reaction to this medicine, it can cause serious problems for your pregnancy. Your baby may not get enough oxygen (fetal distress), or you could go into early (premature) labour.
Call your doctor or go to an emergency department if you have cramping, contractions (the muscles around your baby tighten), or you notice your baby is moving less than usual.
After treatment
After you get all the injections you need, you may need to have regular blood tests. You may need a blood test every few months for up to 1 or 2 years after treatment. Your nurse or doctor will tell you what tests you need. Your blood tests will likely stay positive for syphilis for the rest of your life, even if you’ve been treated.
If you’re pregnant, make sure you tell the doctor or midwife who is delivering your baby about your test results and treatment.
Effects on birth control
The birth control pill, patch, and ring might not work as well when you take Bicillin L-A. To help prevent pregnancy, keep using your regular birth control and use condoms for 7 days after you get the injection to help prevent pregnancy.
Lowering your risk of getting syphilis again
Do not have unprotected oral, vaginal, or anal sex until you and your partner or partners are tested and for 7 days after you and your partner or partners are treated.
The best protection is to have no sex (oral, vaginal, or anal) for 7 days after you and your partner or partners are treated. You can get syphilis again if you have oral, vaginal, or anal sex without a condom with someone who has it.
Where can I learn more?
To see this information online and learn more, visit MyHealth.Alberta.ca/health/pages/conditions.aspx?Hwid=custom.ab_syphilis_bicillin_la_inst.
For 24/7 nurse advice and general health information call Health Link at 811.
Current as of: August 28, 2026
Author: Provincial STI Programs, Primary Care
This material is not a substitute for the advice of a qualified health professional. This material is intended for general information only and is provided on an "as is", "where is" basis. Although reasonable efforts were made to confirm the accuracy of the information, Alberta Health Services does not make any representation or warranty, express, implied or statutory, as to the accuracy, reliability, completeness, applicability or fitness for a particular purpose of such information. Alberta Health Services expressly disclaims all liability for the use of these materials, and for any claims, actions, demands or suits arising from such use.
