This medication is used to treat a wide variety of bacterial infections. It is also used to prevent infection of the heart (bacterial endocarditis) in patients with certain heart diseases who are having surgery. This medication is known as a natural penicillin antibiotic. It works by stopping the growth of bacteria.

Depending on your specific product, this medication is given by injection into a vein or into a muscle. Use exactly as directed by your doctor. The dosage is based on your medical condition and response to treatment. Children's dosage is also based on weight.

If you are giving this medication to yourself at home, learn all preparation and usage instructions from your health care professional. Before using, check this product for particles or discoloration. If either is present, do not use the liquid. Learn how to store and discard medical supplies safely.

Give aminoglycosides (such as gentamicin) separately from this medication. Do not mix together in the same IV fluid.

For the best effect, use this antibiotic at evenly spaced times. To help you remember, use this medication at the same time(s) every day.

Continue to use this medication until the full prescribed amount is finished, even if symptoms disappear after a few days. Stopping the medication too early may result in a return of the infection.

Tell your doctor if your condition lasts or gets worse.

Pain/redness/swelling at injection site may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• joint/muscle pain
• muscle weakness
• swelling of ankles/feet
• dark/cloudy urine
• extreme tiredness
• fast/slow/irregular heartbeat
• new signs of infection (such as sore throat that doesn't go away, fever, chills)
• easy bruising/bleeding
• signs of kidney problems (such as change in the amount of urine)
• numbness/tingling of arms/legs
• seizures
• uncontrolled movements
• confusion

If used to treat syphilis or other spirochetal infections (such as Lyme disease), this medication may cause a condition known as Jarisch-Herxheimer reaction. This condition may occur 1 to 2 hours after you receive the medication and can last up to 24 hours. Notify your doctor right away if you experience any of these symptoms: fever/chills, muscle pain, worsening of skin sores, fast heartbeat, fast breathing, dizziness, flushing.

This medication may rarely cause a severe intestinal condition due to a bacteria called C. difficile. This condition may occur during treatment or weeks to months after treatment has stopped. Tell your doctor right away if you develop:

• diarrhea that doesn't stop
• abdominal or stomach pain/cramping
• blood/mucus in your stool

If you have these symptoms, do not use anti-diarrhea or opioid products because they may make symptoms worse.

Use of this medication for prolonged or repeated periods may result in oral thrush or a new vaginal yeast infection. Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before using this medication, tell your doctor or pharmacist if you are allergic to it; or to penicillin or cephalosporin antibiotics; or if you have any other allergies. This product may contain inactive ingredients (such as corn for products containing dextrose), which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• asthma
• kidney disease

Penicillin may cause live bacterial vaccines (such as typhoid vaccine) to not work well. Tell your health care professional that you are using penicillin before having any immunizations/vaccinations.

Certain products of this medication contain sodium. Consult your doctor or pharmacist if you are on a salt-restricted diet or if you have a condition that could be worsened by an increase in salt intake (such as heart failure).

Certain products of this medication contain potassium. Consult your doctor or pharmacist if you are taking potassium supplements, salt substitutes containing potassium, or medications that can increase potassium (including ACE inhibitors such as lisinopril), or if you have a high potassium level (hyperkalemia).

Older adults may be at greater risk for side effects while using this drug.

Newborns and infants may be at greater risk for side effects while using this drug.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This drug passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

A product that may interact with this drug is:

• methotrexate

This medication may interfere with certain lab tests (such as certain urine glucose tests), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: seizures, confusion, mental/mood changes (such as agitation).

Lab and/or medical tests (such as kidney function, complete blood count, potassium/sodium levels) may be done while you are using this medication. Keep all medical and lab appointments. Consult your doctor for more details.

It is important to get each dose of this medication as scheduled. If you miss a dose, ask your doctor or pharmacist right away for a new dosing schedule. Do not double the dose to catch up.

Consult the product instructions and your pharmacist for storage details. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.