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Nafcillin

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, liver disease.

This medication contains sodium. This could affect you if you are on a salt-restricted diet or if you have a condition which could be worsened with an increase in salt intake (such as heart failure). Consult your doctor or pharmacist for more information.

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

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

Newborns and infants may be a 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.

Side Effects

If this medication is injected into a muscle, pain at the injection site may occur. If this effect lasts or gets worse, notify 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: pain/swelling/skin peeling at injection site (if this drug is injected into a vein), joint/muscle pain, signs of kidney problems (such as change in the amount of urine, pink/bloody/frothy/dark/cloudy urine), extreme tiredness, easy bruising/bleeding, new signs of infection (such as sore throat that doesn't go away, fever), seizures, uncontrolled movements, confusion, irregular heartbeat, muscle cramps, weakness.

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.

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Drug information is selected from data included with permission and copyrighted by First DataBank, Inc. This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your healthcare professional. Always seek the advice of your healthcare professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your healthcare professional. This information does not contain any assurances that this product is safe, effective or appropriate for you.

This information is intended only for residents of the United States. Products sold under the same brand names in other countries may contain different ingredients.

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Information expires December 2025.