Penicillin G benzathine is an antibiotic that is used to treat many types of infections caused by bacteria, including strep or syphilis. Penicillin G benzathine is also used to prevent symptoms of rheumatic fever.

Penicillin G benzathine may also be used for purposes not listed in this medication guide.

Tell your doctor if you have ever had an allergic reaction to an antibiotic.

Penicillin G benzathine is injected into a muscle.

Read and follow all Instructions for Use. Ask your doctor or pharmacist if you need help.

Prepare an injection only when you are ready to give it. Call your pharmacist if the medicine has changed colors or has particles in it.

Do not reuse a needle or syringe. Place them in a puncture-proof "sharps" container and dispose of it following state or local laws. Keep out of the reach of children and pets.

Keep using this medicine even if your symptoms quickly improve. Skipping doses could make your infection resistant to medication. Penicillin G benzathine will not treat a viral infection (flu or a common cold).

Do not inject this medicine near or into an artery, vein, or nerve. Dangerous or fatal side effects could occur.

You may need tests after treatment to make sure your infection has completely cleared.

Store in the refrigerator, do not freeze.

You should not be treated with penicillin G benzathine if you are allergic to penicillin.

Tell your doctor if you have ever had:

• an allergic reaction to a cephalosporin antibiotic (Keflex, Omnicef, and others);

• any type of allergy;

• asthma or breathing problems;

• heart disease; or

• kidney disease.

Tell your doctor if you are pregnant or breastfeeding.

Call your doctor for instructions if you miss a dose.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose may cause a seizure.

Avoid taking anti-diarrhea medicine without first asking your doctor. Diarrhea may be a sign of a new infection.

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Some side effects may occur if the medicine has been accidentally injected near a vein or nerve. Tell your doctor right away if you have:

• pain, numbness, tingling, burning, or feeling cold;

• pale or mottled skin, blue-colored lips, fingers, or toes;

• severe pain, tingling, weakness, or swelling in your lower leg;

• weakness in your arms or legs; or

• blistering, peeling, discoloration, or painful skin changes where the medicine was injected.

Also call your doctor at once if you have:

• severe stomach pain, diarrhea that is watery or bloody (even if it occurs months after your last dose);

• a light-headed feeling, like you might pass out;

• slow heart rate, weak pulse, fainting, slow breathing (breathing may stop);

• pounding heartbeats or fluttering in your chest;

• confusion, agitation, hallucinations (seeing or hearing things that aren't real), extreme fear;

• a seizure;

• pain, swelling, warmth, redness, bruising, bleeding, or a lump where the medicine was injected;

• easy bruising or bleeding;

• pale or yellowed skin, dark colored urine;

• urination problems; or

• signs of a new infection--fever, chills, mouth sores, warmth or redness under your skin, vaginal itching or discharge.

Common side effects of penicillin G benzathine may include:

• nausea, vomiting, diarrhea;

• itching, sweating, allergic reaction;

• flushing (sudden warmth, redness, or tingly feeling);

• feeling anxious, nervous, weak, or tired;

• headache, dizziness, drowsiness;

• muscle or joint pain; or

• pain, swelling, bruising, or a hard lump where an injection was given.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Tell your doctor about all your other medicines, especially:

• tetracycline; or

• probenecid.

This list is not complete. Other drugs may affect penicillin G benzathine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.