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Penicillin G (Potassium, Sodium) Injection

pronounced as (pen" I sil' in)

Why is this medication prescribed?

Penicillin G injection is used to treat and prevent certain infections caused by bacteria. Penicillin G injection is in a class of medications called penicillins. It works by killing bacteria that cause infections.

Antibiotics such as penicillin G injection will not work for colds, flu, or other viral infections. Taking antibiotics when they are not needed increases your risk of getting an infection later that resists antibiotic treatment.

How should this medicine be used?

Penicillin G injection comes as a powder to be mixed with water and as a premixed product. Penicillin G injection is usually injected into a muscle or vein but may also be given directly into the lining of the chest cavity, into the fluid surrounding the spinal cord, or into a joint or other areas. The number of doses you receive each day and the total length of your treatment depend on your general health, the type of infection that you have, and how well you respond to the medication.

You may receive penicillin G injection in a hospital or you may administer the medication at home. If you will be receiving penicillin G injection at home, your healthcare provider will show you how to use the medication. Be sure that you understand these directions, and ask your healthcare provider if you have any questions.

You should begin to feel better during the first few days of treatment with penicillin G injection. If your symptoms do not improve or get worse, call your doctor.

Use penicillin G injection for as long as your doctor tells you that you should, even if you feel better. If you stop using penicillin G injection too soon or skip doses, your infection may not be completely treated and the bacteria may become resistant to antibiotics.

If you are using penicillin G injection to treat certain infections such as syphilis (a sexually transmitted disease), Lyme disease (an infection transmitted by tick bites that may cause problems with the heart, joints, and nervous system), or relapsing fever (an infection transmitted by tick bites that causes repeated episodes of fever), you may experience a reaction beginning one or two hours after receiving your first dose of this medication and lasting for 12 to 24 hours. Tell your doctor if you experience any of the following symptoms: fever, chills, muscle aches, headache, worsening of skin sores, fast heartbeat, fast breathing, and flushing.

Other uses for this medicine

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What special precautions should I follow?

Before receiving penicillin G injection,

  • tell your doctor and pharmacist if you are allergic to penicillin G injection; penicillin antibiotics; cephalosporin antibiotics such as cefaclor, cefadroxil, cefazolin (Ancef, Kefzol), cefditoren (Spectracef), cefepime (Maxipime), cefixime (Suprax), cefotaxime (Claforan), cefoxitin, cefpodoxime, cefprozil, ceftazidime (Fortaz, Tazicef), ceftibuten (Cedax), ceftriaxone (Rocephin), cefuroxime (Ceftin, Zinacef), and cephalexin (Keflex); or any other medications. Ask your doctor or pharmacist if you are not sure if a medication you are allergic to belongs to one of these groups of medications. Also tell your doctor if you are allergic to any of the ingredients in penicillin G injection. Ask your pharmacist for a list of the ingredients.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: aspirin; chloramphenicol; diuretics ('water pills') such as ethacrynic acid (Edecrin) and furosemide (Lasix); erythromycin (Ery-tab, E.E.S., others); indomethacin (Indocin, Tivorbex); probenecid (Probalan); sulfa antibiotics; and tetracycline (Achromycin). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • tell your doctor if you are on a low sodium or potassium diet, and if you have or have ever had asthma, allergies, hay fever, hives, heart failure, or kidney or liver disease.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while receiving penicillin G injection, call your doctor.

What special dietary instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do if I forget a dose?

Use the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not use a double dose to make up for a missed one.

What side effects can this medication cause?

Penicillin G injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • nausea
  • vomiting
  • pain, swelling, or redness in the area where the medication was injected

Some side effects can be serious. If you experience any of these symptoms, stop using penicillin G injection and call your doctor immediately or get emergency medical treatment:

  • rash
  • hives
  • itching
  • difficulty breathing or swallowing
  • swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
  • hoarseness
  • fever
  • muscle or joint pain
  • stomach pain
  • severe diarrhea (watery or bloody stools) with or without fever and stomach cramps that may occur up to 2 months or more after your treatment
  • unusual bleeding or bruising
  • blood in the urine
  • seizures
  • weakness
  • fast, slow, or irregular heartbeat
  • return of fever, sore throat, chills, or other signs of infection

Penicillin G injection may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

In case of emergency/overdose

In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

Symptoms of overdose may include the following:

  • agitation
  • confusion
  • jerking movements
  • seeing things or hearing voices that do not exist
  • seizures
  • coma
  • weakness
  • fast, slow, or irregular heartbeat

What other information should I know?

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body's response to penicillin G injection.

Before having any laboratory test, tell your doctor and the laboratory personnel that you are receiving penicillin G injection.

If you are diabetic and test your urine for sugar, use Clinistix or TesTape (not Clinitest) to test your urine while taking this medication.

Ask your pharmacist any questions you have about penicillin G injection.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

Brand names

  • Pfizerpen®

Other names

  • Benzylpenicillin Potassium or Sodium
  • Crystalline Penicillin
Last Revised - 02/15/2016