Oxacillin

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Oxacillin Prescribing Information

Oxacillin is indicated in the treatment of infections caused by penicillinase producing staphylococci which have demonstrated susceptibility to the drug. Cultures and susceptibility tests should be performed initially to determine the causative organism and its susceptibility to the drug. (See CLINICAL PHARMACOLOGY - Susceptibility Test Methods.)

Oxacillin may be used to initiate therapy in suspected cases of resistant staphylococcal infections prior to the availability of susceptibility test results. Oxacillin should not be used in infections caused by organisms susceptible to penicillin G. If the susceptibility tests indicate that the infection is due to an organism other than a resistant

Staphylococcus

, therapy should not be continued with oxacillin.

To reduce the development of drug-resistant bacteria and maintain the effectiveness of Oxacillin Injection, USP and other antibacterial drugs, Oxacillin Injection, USP should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

Oxacillin Injection, USP supplied as a premixed frozen solution is to be administered as a continuous or intermittent intravenous infusion. The usual dose recommendation is as follows:

Adults

250-500 mg

I.V. every 4-6 hours (mild to moderate infections)

1 gram

I.V. every 4-6 hours (severe infections)

This container system may be inappropriate for the dosage requirements for children, infants and neonates. Other dosage forms may be more appropriate.

Bacteriologic studies to determine the causative organisms and their susceptibility to oxacillin should always be performed. Duration of therapy varies with the type of severity of infection as well as the overall condition of the patient; therefore, it should be determined by the clinical and bacteriological response of the patient. In severe staphylococcal infections, therapy with oxacillin should be continued for at least 14 days. Therapy should be continued for at least 48 hours after the patient has become afebrile, asymptomatic, and cultures are negative. Treatment of endocarditis and osteomyelitis may require a longer duration of therapy.

Concurrent administration of oxacillin and probenecid increases and prolongs serum penicillin levels. Probenecid decreases the apparent volume of distribution and slows the rate of excretion by competitively inhibiting renal tubular secretion of penicillin. Penicillin-probenecid therapy is generally limited to those infections where very high serum levels of penicillin are necessary.

With intravenous administration, particularly in elderly patients, care should be taken because of the possibility of thrombophlebitis.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration whenever solution and container permit.

Do not add supplementary medication to Oxacillin Injection, USP.

Store in a freezer capable of maintaining a temperature of -20°C/-4°F or less.

The reported incidence of allergic reactions to penicillin ranges from 0.7 to 10 percent (see

WARNINGS

Serious and occasionally fatal hypersensitivity (anaphylactic shock with collapse) reactions have occurred in patients receiving penicillin. The incidence of anaphylactic shock in all penicillin-treated patients is between 0.015 and 0.04 percent. Anaphylactic shock resulting in death has occurred in approximately 0.002 percent of the patients treated. Although anaphylaxis is more frequent following parenteral administration, it has occurred in patients receiving oral penicillins.

When penicillin therapy is indicated, it should be initiated only after a comprehensive patient drug and allergy history has been obtained. If an allergic reaction occurs, the drug should be discontinued and the patient should receive supportive treatment,

e.g.

, artificial maintenance of ventilation, pressor amines, antihistamines, and corticosteroids. Individuals with a history of penicillin hypersensitivity may also experience allergic reactions when treated with a cephalosporin.

Clostridium difficile

associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including Oxacillin Injection, USP, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of

C. difficile

produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of

C. difficile

cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.

If CDAD is suspected or confirmed, ongoing antibiotic use not directed against

C. difficile

may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of

C. difficile

, and surgical evaluation should be instituted as clinically indicated.

). Sensitization is usually the result of treatment but some individuals have had immediate reactions when first treated. In such cases, it is thought that the patients may have had prior exposure to the drug via trace amounts present in milk and vaccines.

Two types of allergic reactions to penicillins are noted clinically, immediate and delayed.

Immediate reactions usually occur within 20 minutes of administration and range in severity from urticaria and pruritus to angioneurotic edema, laryngospasm, bronchospasm, hypotension, vascular collapse and death. Such immediate anaphylactic reactions are very rare (see

WARNINGS

e.g.

Clostridium difficile

C. difficile

produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of

C. difficile

If CDAD is suspected or confirmed, ongoing antibiotic use not directed against

C. difficile

may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of

C. difficile

, and surgical evaluation should be instituted as clinically indicated.

) and usually occur after parenteral therapy but have occurred in patients receiving oral therapy. Another type of immediate reaction, an accelerated reaction, may occur between 20 minutes and 48 hours after administration and may include urticaria, pruritus, and fever. Although laryngeal edema, laryngospasm, and hypotension occasionally occur, fatality is uncommon. Delayed allergic reactions to penicillin therapy usually occur after 48 hours and sometimes as late as 2 to 4 weeks after initiation of therapy. Manifestations of this type of reaction include serum sickness-like symptoms (

i.e.

, fever, malaise, urticaria, myalgia, arthralgia, abdominal pain) and various skin rashes. Nausea, vomiting, diarrhea, stomatitis, black or hairy tongue, and other symptoms of gastrointestinal irritation may occur, especially during oral penicillin therapy.

Oxacillin Injection, USP is a sterile injectable product containing oxacillin which is added as oxacillin sodium, a semisynthetic penicillin derived from the penicillin nucleus, 6-aminopenicillanic acid. The chemical name of oxacillin sodium is 4-Thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid, 3,3-dimethyl-6-[[(5-methyl-3-phenyl-4- isoxazolyl)carbonyl]-amino]-7-oxo-, monosodium salt, monohydrate, [2S-(2α,5α,6ß)]-. It is resistant to inactivation by the enzyme penicillinase (beta-lactamase). The molecular formula of oxacillin sodium is C₁₉H₁₈N₃NaO₅S•H₂O. The molecular weight is 441.44.

The structural formula of oxacillin sodium is as follows:

Oxacillin Injection, USP is a frozen, iso-osmotic, sterile, nonpyrogenic premixed 50 mL solution containing 2 g of oxacillin added as oxacillin sodium. Dextrose, USP has been added to the above dosages to adjust osmolality (approximately 300 mg as dextrose hydrous to the 2 g dosages respectively). Sodium Citrate Hydrous, USP has been added as a buffer (approximately 300 mg to the 2 g dosage). The pH has been adjusted with hydrochloric acid and may have been adjusted with sodium hydroxide. The pH is 6.5 (6.0 to 8.5). The solution is intended for intravenous use after thawing to room temperature.

This

Galaxy

container is fabricated from a specially designed multilayer plastic. Solutions are in contact with the polyethylene layer of this container and can leach out certain chemical components of the plastic in very small amounts within the expiration period. The suitability of the plastic has been confirmed in tests in animals according to the USP biological tests for plastic containers, as well as by tissue culture toxicity studies.

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