Antibiotics Home > Nafcillin Warnings and Precautions

While nafcillin can be an effective antibiotic for many people, it may cause dangerous allergic reactions, serious side effects, or other complications for some people. In particular, people who have kidney or liver disease should talk to their healthcare provider before using nafcillin. Other safety precautions include warnings for people who have a penicillin allergy and those who are taking certain medications.

What Should I Tell My Healthcare Provider?

You should talk with your healthcare provider prior to receiving nafcillin if you have:
  • Kidney disease, such as kidney failure (renal failure)
  • Liver disease, such as hepatitis, liver failure, or cirrhosis
  • An allergy to penicillin or penicillin antibiotics
  • Any other allergies, including to foods, dyes, or preservatives.
Also, let your healthcare provider know if you are:
  • Pregnant or thinking of becoming pregnant
  • Breastfeeding.
You should also tell your healthcare provider about all other medications you are taking, including prescription and nonprescription medicines, vitamins, and herbal supplements.

Specific Precautions and Warnings for Nafcillin

Some warnings and precautions to be aware of prior to using this medication include the following:
  • If you have liver or kidney disease, you may need a lower or less-frequent nafcillin dosage. Using normal dosages of nafcillin in people with liver and/or kidney problems can lead to serious complications.
  • Nafcillin is an antibiotic that belongs to the penicillin group of antibiotics. People can be severely allergic to penicillin. Do not take this medication if you are allergic to penicillin medications. Because an allergic reaction to nafcillin can be extremely dangerous, let your healthcare provider know immediately you notice any signs of an allergic reaction, such as:
    • A rash
    • Itching
    • Hives
    • Wheezing
    • Swelling of the mouth or lips
    • Difficulty breathing.
  • Let your healthcare provider know if you experience bloody or watery diarrhea. While diarrhea is a common side effect of nafcillin, bloody or watery diarrhea may be a sign of a serious reaction to nafcillin that can occur when certain bacteria (Clostridium difficile) overgrow in the colon. This severe reaction can occur long after you stop taking nafcillin and can be life-threatening.
  • Antibiotics, including nafcillin, can sometimes cause yeast infections, as they can get rid of "good" bacteria that help protect against yeast infections. Let your healthcare provider know if you develop a vaginal yeast infection or thrush (a yeast infection of the mouth) during treatment.
  • Nafcillin should not be used to treat viruses, such as the common cold or the flu. Nafcillin is completely ineffective for treating viruses, and such use can lead to bacterial resistance to nafcillin.
  • Nafcillin is a pregnancy Category B medication. This means that it is probably safe for use during pregnancy, although the full risks are currently unknown. Talk to your healthcare provider about the risks and benefits of using nafcillin during pregnancy (see Nafcillin and Pregnancy for more information).
  • Nafcillin probably passes through breast milk. Therefore, if you are breastfeeding or plan to start, talk with your healthcare provider prior to using nafcillin (see Nafcillin and Breastfeeding for more information).
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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