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Nafcillin is a narrow-spectrum, beta-lactamase resistant penicillin. As a custom pharmacy drug it fights bacteria growth and is sometimes a physician's preference treating naturally resistant bacteria. Nafcillin is often selected to treat bacterial infections brought on by Gram-positive species and especially resistant staphylococcus species.


Nafcillin is generally administered as an injection, typically given at your physician's office, clinic, or hospital. Nafcillin can also be administered via intravenous solutions and oral capsules. If your physician recommends at-home use of the injection form, be sure that you receive step-by-step instructions on how to inject yourself. If you have any questions on this procedure, ask your physician for further explanation.


Nafcillin has been known to cause side effects in some patients. Unwanted side effects can be fleeting or may linger. If you experience any side effect that lingers, or gets worse, see your physician.

Common Nafcillin Injection Side Effects:

The most commonly experienced side effect of nafcillin injection is diarrhea.

Severe Side Effects:

Nafcillin may possibly cause severe side effects in some patients. It is important to be knowledgeable and aware of side effects so you can act accordingly if you experience any. Severe side effects can be serious and harmful. If you experience anything that is severe, see your physician right away or go to a medical treatment facility for care immediately.

Partial List of Some Severe Nafcillin Injection Side Effects:

  • Swelling (face, throat, tongue, lips, eyes)
  • Swelling (hands, feet, ankles, or lower legs)
  • Hoarseness
  • Dizziness and/or Fainting
  • Severe Diarrhea
  • Difficulty Breathing
  • Swallowing Problems
  • Warmth, Redness, and/or Swelling (possibly pain) near Injection Site
  • Bloody or Watery Stools (possibly as late as 2 months or more after treatment)
  • Rash and/or Hives and/or Fever and/or Itching (possibly with stomach/muscle pain)
  • Rash and/or Hives and/or Fever and/or Itching (possibly with joint pain)

Severe Allergic Reaction:

Severe allergic reactions can occur with any medication. Watch for signs of potentially severe allergic reactions. Seek medical attention at once if you experience any of the following:

  • Itching and/or Swelling (face, throat, lips, and tongue)
  • Severe Dizziness
  • Fever
  • Muscle or Joint Pain
  • Stomach Pain
  • Rash
  • Trouble Breathing

WARNING: Allergic reactions to nafcillin can sometimes be delayed by as much as four weeks, so be prepared, know the signs of allergic reaction, and get medical help immediately if you experience any of the signs.

IMPORTANT NOTE ON NAFCILLIN ORAL: If you are prescribed an oral form of nafcillin, consult with your doctor on possible side effects so you know what to watch for and how to respond if you experience any.


All patients, especially anyone who may have an allergy to penicillin, should consult with their physician before using this drug.

TALK TO YOUR PHYSICIAN: If you have a history of kidney disease, liver disease, or asthma, talk to your physician to decide if nafcillin is safe for your use.

Nafcillin is contraindicated for breastfeeding.

Nafcillin may be contraindicated for pregnancy, in some cases. Only your doctor will know if nafcillin is safe for your use. Do not use nafcillin if you are pregnant or planning to become pregnant unless your physician has approved your use of the drug.

CAUTION: Consult with your physician before using nafcillin if you have any of the following conditions:

  • Clostridium Difficile Infection
  • Severe Renal Impairment

Ask your physician about all possible contraindications for the use of nafcillin

  • "It is rare to find health professionals who are so willing to educate the patient on what they need to know."

    Clair C. | West Hollywood, CA