"A new consumer-friendly form ( is now available for making reports to MedWatch, the Food and Drug Administration's (FDA) on-line system for collecting information about serious problems with drugs, medical devices and other FDA-"...
Pfizerpen Consumer (continued)
Remember that your doctor has prescribed this medication because he or she 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 (e.g., fever, persistent sore throat), easy bruising/bleeding, change in the amount of urine, numbness/tingling of arms/legs, seizures, uncontrolled movements, confusion.
If used to treat syphilis or other spirochetal infections (e.g., 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 immediately 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 (Clostridium difficile-associated diarrhea) due to a type of resistant bacteria. This condition may occur weeks to months after treatment has stopped. Do not use anti-diarrhea products or narcotic pain medications if you have any of these symptoms because these products may make them worse. Tell your doctor immediately if you develop: persistent diarrhea, abdominal or stomach pain/cramping, blood/mucus in your stool.
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.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
Read the Pfizerpen (penicillin g potassium) Side Effects Center for a complete guide to possible side effects
PRECAUTIONS: 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.
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 (e.g., congestive 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 (e.g., ACE inhibitors such as lisinopril), or if you have a high potassium level (hyperkalemia).
Kidney function declines as you grow older. This medication is removed by the kidneys. Therefore, elderly people may be at greater risk for side effects while using this drug.
Kidney function is not fully developed in newborns and infants. This medication is removed by the kidneys. Therefore, 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 breast-feeding.
Additional Pfizerpen Information
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Find out what women really need.