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Medications and Drugs

Brand Names: Nallpen, Unipen

Generic Name: nafcillin (injection) (Pronunciation: naf SIL in)

What is nafcillin (Nallpen, Unipen)?

Nafcillin is an antibiotic in the penicillin group of drugs. It fights bacteria in your body.

Nafcillin is used to treat many different types of infections, especially those caused by staphylococcus bacteria ("staph" infections).

Nafcillin may also be used for other purposes not listed in this medication guide.

What are the possible side effects of nafcillin (Nallpen, Unipen)?

Get emergency medical help if you have any of these signs of an allergic reaction: hives, itching; fever, stomach pain, muscle or joint pain; difficulty breathing; swelling of your face, lips, tongue, or throat. A delayed allergic reaction to nafcillin can occur as few as 2 days to as many as 4 weeks after you use the medication.

Call your doctor at once if you have any of these serious side effects:

  • diarrhea that is watery or bloody;
  • fever, chills, body aches, flu symptoms, sores in your mouth and throat;
  • skin rash, bruising, severe tingling, numbness, pain, muscle weakness;
  • blood in your urine, urinating less than usual or not at all; or
  • pain, swelling, tenderness, or skin changes where the medicine was injected.

Less serious side effects are more likely to occur, such as:

  • nausea, vomiting;
  • vaginal itching or discharge; or
  • black or "hairy" tongue.

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.

What is the most important information I should know about nafcillin (Nallpen, Unipen)?

You should not use this medication if you are allergic to nafcillin or to any other penicillin antibiotic, such as amoxicillin (Amoxil), ampicillin (Omnipen, Principen), oxacillin (Bactocill), penicillin (Beepen-VK, Ledercillin VK, Pen-V, Pen-Vee K, Pfizerpen, V-Cillin K, Veetids), and others.

Before using nafcillin, tell your doctor if you are allergic to cephalosporins such as Ceftin, Cefzil, Keflex, Omnicef, and others, or if you have asthma, liver or kidney disease, or a history of any type of allergy.

Use this medication for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Nafcillin is usually given for up to 2 days after lab tests show that the infection has cleared.

Antibiotic medicines can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or bloody, stop taking nafcillin and call your doctor. Do not use anti-diarrhea medicine unless your doctor tells you to.



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.

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