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Oxacillin (penicillin-derivative antibiotic)

Uses|Precautions & warnings|Side effects|Interactions|Dosage

Oxacillin sodium is an antibiotic under the class of penicillin. It is a semisynthetic form of penicillin that has penicillinase resistance and is acid-stable. Like other penicillins, oxacillin works by binding to penicillin-binding proteins embedded on the inner membrane of the cell wall of certain bacteria. This weakens and deforms the structure of the bacterium, causing it to be destroyed.



What is oxacillin used for?

Oxacillin is indicated mainly to treat Staphylococcal infections that are resistant to benzylpenicillin. There are over 30 species of Staphylococcus, with S. aureus causing the majority of these infections.

Infections include:

  • Cutaneous (skin) infection
  • Sepsis (infection in the blood with accompanied immune response)
  • Osteitis (bone) infection
  • Endocarditis (the inner lining of the heart muscles)
  • Food poisoning
  • Pneumonia
  • Toxic shock syndrome (commonly attributed to tampon use)

How should I take oxacillin?

Oxacillin is primarily available in the parenteral (IV/IM) dosage form. This medication requires reconstitution with sterile water for injection prior to administration. Once reconstituted, this drug should be administered immediately. Do not take parenteral medications by mouth or by other routes.

How do I store oxacillin?

This product is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store it in the bathroom or the freezer.

There may be different brands of this drug that may have different storage needs. So, it is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush this product down the toilet or pour them into a drain unless instructed to do so. Additionally, it is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using oxacillin?

Before using this drug, tell your doctor if you are/have:

  • Pregnant or breastfeeding.
  • Taking any other medicines. This includes any prescription, OTC, and herbal remedies.
  • An allergy to any of the ingredients of this product or other pencillin drugs.
  • Any other illnesses, disorders, or medical conditions.

Is it safe during pregnancy or breastfeeding?

This drug is a pregnancy category B drug. Human and animal studied have not shown evidence of causing fetal or reproductive harm. This drug should only be used during pregnancy if there is a clear need and the potential benefits outweigh the potential risks, as determined by your doctor.

This drug is excreted in breast milk. Do not breastfeed or pump milk for storage while taking this medication.

Side effects

What side effects can occur when using oxacillin?

Like all drugs, this product may have side effects. If they occur, side effects are generally mild and resolve once treatment is finished or the dose is lowered. Some reported side effects include:

  • Gastrointestinal upset
    • Nausea
    • Vomiting
    • Diarrhea
    • Clostridium difficile-associated diarrhea or pseudomembranous colitis (potentially fatal)
  • Allergic reaction
    • Fever
    • Rash
    • Leukopenia
  • Anaphylaxis (potentially fatal)
    • Trouble breathing
    • Tightening or collapse of airways
  • Hepatotoxicity
    • Increased AST
  • Acute interstitial nephritis
    • Hematuria
  • Serum sickness-like reactions

However, not everyone experiences these side effects. In addition, some people may experience other side effects. So, if you have any concerns about a side effect, please consult your doctor or pharmacist.


What drugs may interact with oxacillin?

This medication may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects.

To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist.

Drugs with known interactions:

  • BCG vaccine
  • Cholera vaccine
  • Typhoid vaccine
  • Aminoglycosides
  • Dichlorphenamide
  • Lactobacillus and estriol
  • Methotrexate
  • Mycophenolate
  • Probenecid
  • Sodium picosulfate
  • Tetracyclines
  • Vitamin K antagonists (e.g. warfarin)

If you experience an adverse drug interaction, stop taking this drug and continue taking your other medication. Inform your doctor immediately to reevaluate your treatment plan. Approaches include dose adjustment, drug substitution, or ending therapy.

Does food or alcohol interact with oxacillin?

This drug may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with oxacillin?

This drug may interact with underlying conditions. This interaction may worsen your health condition or alter the way the drug works. Therefore, it is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

  • Hypersensitivity to β-lactams (e.g. penicillin, cephalosporins)
  • Asthma


The information provided is not a substitute for any medical advice. Therefore, you should always consult with your doctor or pharmacist before using any medication.

What is the dose for an adult?

For reconstitution of the suspension

Intramuscular (IM)

  • Add 5.7 mL or 11.4 mL of sterile water for injection to the vial containing 1 g or 2 g of oxacillin, respectively, to create a solution containing 167 mg/mL (250 mg/1.5 mL).

Intravascular (IV)

  • Add 10 mL or 20 mL of sterile water for injection or NaCl 0.45% or 0.9% injection to the vial containing 1 g or 2 g of oxacillin, respectively.
  • For IV infusion, dilute further with a compatible IV solution to a concentration of 0.5-40 mg/mL.

For susceptible Staphylococcous infections

Administer 250-500 mg every 4 to 6 hours, by IM, slow IV injection over 10 minutes or IV infusion. Increase the dose to 1 g given 4 to 6 hours for severe infections.

What is the dose for a child?

For infections due to benzylpenicillin-resistant staphylococci

  • Body weight <40 kg: 50-100 mg/kg/day administered via IV in divided doses.
  • Premature and neonate babies: 25 mg/kg/day administered via IV

How is oxacillin available?

This drug is available in the following brands, dosage forms and strengths:

  • Cilvex powder for injection 500 mg/vial
  • Oxal powder for injection 500 mg/vial
  • Oxan powder for injection 500 mg/vial
  • Oxapen powder for injection 500 mg/vial
  • Wydox powder for injection 500 mg/vial

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to the nearest emergency room.

What should I do if I miss a dose?

If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.


Oxacillin https://www.mims.com/philippines/drug/info/oxacillin Accessed June 15, 2021

Oxacillin Injection USP https://www.accessdata.fda.gov/drugsatfda_docs/label/2015/050640s017lbl.pdf Accessed June 15, 2021

Oxacillin Sodium. https://pubchem.ncbi.nlm.nih.gov/compound/Oxacillin-sodium. Accessed June 15, 2021

Oxacillin http://www.antimicrobe.org/new/drugpopup/Oxacillin.pdf Accessed June 11, 2021

Oxacillin. Lexi-Drugs. Lexicomp. Wolters Kluwer Health, Inc. Riverwoods, IL. Accessed June 15, 2021. http://online.lexi.com

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Written by Stephanie Nicole Nera, RPh, PharmD Updated Jun 16