Rx Only

To reduce the development of drug-resistant bacteria and maintain the effectiveness of cefazolin and other antibacterial drugs, cefazolin should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.

DESCRIPTION

Cefazolin for Injection, USP, is a sterile, lyophilized, semisynthetic cephalosporin for intravenous administration. It is the sodium salt of 3-{[(5-methyl-1,3,4-thiadiazol-2-yl)thio]-methyl}-8-oxo-7- [2-(1H-tetrazol-1-yl)acetamido]-5-thia-1-azabicyclo [4.2.0]oct-2-ene-2-carboxylic acid. Each Pharmacy Bulk Package contains 48 mg (2.1 mEq) of sodium per 1 gram of cefazolin sodium. Cefazolin for Injection, USP, is supplied in 100 grams and 300 grams SmartPak®Pharmacy Bulk Packages equivalent to 100 grams or 300 grams of cefazolin. Each Pharmacy Bulk Package contains cefazolin sodium equivalent to 100 grams or 300 grams of cefazolin.

The molecular formula is C14H13N8NaO4S3. The molecular weight is 476.49.

The structural formula is as follows:

The pH of the reconstituted solution is between 4 and 6.

BEFORE ADMINISTRATION, THIS PHARMACY BULK PACKAGE REQUIRES RECONSTITUTION TO A CONCENTRATION OF 100 mg per mL OR 200 mg per mL AND TRANSFER INTO STERILE SYRINGES. A Pharmacy Bulk Package is a container of a sterile preparation for intravenous use that contains many single doses. The contents are intended for use in a pharmacy admixture service and are restricted to the preparation of admixtures for intravenous infusion.

CLINICAL PHARMACOLOGY

Studies have shown that following intravenous administration of cefazolin to normal volunteers, mean serum concentrations peaked at approximately 185 mcg/mL and were approximately 4 mcg/mL at 8 hours for a 1 gram dose.

The serum half-life for cefazolin is approximately 1.8 hours following IV administration.

In a study (using normal volunteers) of constant intravenous infusion with dosages of 3.5 mg/kg for 1 hour (approximately 250 mg) and 1.5 mg/kg the next 2 hours (approximately 100 mg), cefazolin produced a steady serum concentration at the third hour of approximately 28 mcg/mL.

Studies in patients hospitalized with infections indicate that cefazolin produces mean peak serum concentrations approximately equivalent to those seen in normal volunteers.

Bile levels in patients without obstructive biliary disease can reach or exceed serum levels by up to five times; however, in patients with obstructive biliary disease, bile levels of cefazolin are considerably lower than serum levels (< 1 mcg/mL).

In synovial fluid, the cefazolin level becomes comparable to that reached in serum at about 4 hours after drug administration.

Studies of cord blood show prompt transfer of cefazolin across the placenta. Cefazolin is present in very low levels in the milk of nursing mothers.

Cefazolin is excreted unchanged in the urine. In the first 6 hours approximately 60% of the drug is excreted in the urine and this increases to 70% to 80% within 24 hours.

In patients undergoing peritoneal dialysis (2 L/hr.), cefazolin produced mean serum levels of approximately 10 and 30 mcg/mL after 24 hours' instillation of a dialyzing solution containing 50 mg/L and 150 mg/L, respectively. Mean peak levels were 29 mcg/mL (range 13 to 44 mcg/mL) with 50 mg/L (3 patients), and 72 mcg/mL (range 26 to 142 mcg/mL) with 150 mg/L (6 patients). Intraperitoneal administration of cefazolin is usually well tolerated.

Controlled studies on adult normal volunteers, receiving 1 gram 4 times a day for 10 days, monitoring CBC, SGOT, SGPT, bilirubin, alkaline phosphatase, BUN, creatinine, and urinalysis, indicated no clinically significant changes attributed to cefazolin.

Microbiology

In vitro tests demonstrate that the bactericidal action of cephalosporins results from inhibition of cell wall synthesis. Cefazolin has been shown to be active against most strains of the following microorganisms both in vitro and in clinical infections as described in INDICATIONS AND USAGE:

Gram-Positive Aerobes:

Staphylococcus aureus (including beta-lactamase-producing strains)

Staphylococcus epidermidis

Streptococcus pyogenes, Streptococcus agalactiae and other strains of streptococci

Streptococcus pneumoniae

Methicillin-resistant staphylococci are uniformly resistant to cefazolin, and many Enterococcus strains are resistant.

Gram-Negative Aerobes:

Escherichia coli

Proteus mirabilis

Most strains of indole positive Proteus (Proteus vulgaris), Enterobacter spp., Morganella morganii, Providencia rettgeri and Pseudomonas spp. are resistant to cefazolin.

Susceptibility Tests:

Diffusion Techniques:

Quantitative methods that require measurement of zone diameters provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure1 that has been recommended for use with disks to test the susceptibility of microorganisms to cefazolin uses the 30-mcg cefazolin disk. Results of the standardized single-disk susceptibility test1 with a 30-mcg cefazolin disk should be interpreted according to the following criteria:

RECOMMENDED RANGES FOR CEFAZOLIN SUSCEPTIBILITY TESTING

Standardized single-disk susceptibility test should be performed ONLY with a 30-mcg cefazolin disk.

A report of “Susceptible” indicates that the pathogen is likely to be inhibited by usually achievable concentrations of the antimicrobial compound in the blood. A report of “Intermediate” indicates that the result should be considered equivocal, and, if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug is physiologically concentrated or in situations where high dosage of the drug can be used. This category also provides a buffer zone that prevents small uncontrolled technical factors form causing major discrepancies in interpretation. A report of “Resistant” indicates that usually achievable concentrations of the antimicrobial compound in the blood are unlikely to be inhibitory and that other therapy should be selected.

Standardized susceptibility test procedures require the use of laboratory control microorganisms. The 30-mcg cefazolin disk should provide the following zone diameters in these laboratory test quality control strains:

The cefazolin disk should not be used for testing susceptibility to other cephalosporins.

Dilution Techniques:

Quantitative methods that are used to determine minimum inhibitory concentrations provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure uses a standardized dilution method2 (broth, agar or microdilution) or equivalent with cefazolin powder. The MIC values obtained should be interpreted according to the following criteria:

Interpretation should be as stated above for results using diffusion techniques.

As with standard diffusion techniques, dilution methods require the use of laboratory control microorganisms. Standard cefazolin powder should provide the following MIC values:

INDICATIONS AND USAGE

Cefazolin for Injection is indicated in the treatment of the following serious infections due to susceptible organisms:

Respiratory Tract Infections: Due to S. pneumoniae, S. aureus (including beta-lactamase-producing strains) and S. pyogenes. Injectable benzathine penicillin is considered to be the drug of choice in treatment and prevention of streptococcal infections, including the prophylaxis of rheumatic fever.

Cefazolin is effective in the eradication of streptococci from the nasopharynx; however, data establishing the efficacy of cefazolin in the subsequent prevention of rheumatic fever are not available.

Urinary Tract Infections: Due to E. coli, P. mirabilis.

Skin and Skin Structure Infections: Due to S. aureus (including beta-lactamase-producing strains), S. pyogenes, and other strains of streptococci.

Biliary Tract Infections: Due to E. coli, various strains of streptococci, P. mirabilis, and S. aureus.

Bone and Joint Infections: Due to S. aureus.

Genital Infections: (i.e., prostatitis, epididymitis) due to E. coli, P. mirabilis.

Septicemia: Due to S. pneumoniae, S. aureus (including beta-lactamase-producing strains), P. mirabilis, E. coli.

Endocarditis: Due to S. aureus (including beta-lactamase-producing strains) and S. pyogenes.

Appropriate culture and susceptibility studies should be performed to determine susceptibility of the causative organism to cefazolin.

Perioperative Prophylaxis: The prophylactic administration of cefazolin preoperatively, intraoperatively, and postoperatively may reduce the incidence of certain postoperative infections in patients undergoing surgical procedures which are classified as contaminated or potentially contaminated (e.g., vaginal hysterectomy, and cholecystectomy in high-risk patients such as those older than 70 years, with acute cholecystitis, obstructive jaundice, or common duct bile stones).

The perioperative use of cefazolin may also be effective in surgical patients in whom infection at the operative site would present a serious risk (e.g., during open-heart surgery and prosthetic arthroplasty).

The prophylactic administration of cefazolin should usually be discontinued within a 24-hour period after the surgical procedure. In surgery where the occurrence of infection may be particularly devastating (e.g., open-heart surgery and prosthetic arthroplasty), the prophylactic administration of cefazolin may be continued for 3 to 5 days following the completion of surgery.

If there are signs of infection, specimens for cultures should be obtained for the identification of the causative organism so that appropriate therapy may be instituted.

(See DOSAGE AND ADMINISTRATION.)

To reduce the development of drug-resistant bacteria and maintain the effectiveness of cefazolin and other antibacterial drugs, cefazolin 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.

CONTRAINDICATIONS

CEFAZOLIN FOR INJECTION IS CONTRAINDICATED IN PATIENTS WITH KNOWN ALLERGY TO THE CEPHALOSPORIN GROUP OF ANTIBIOTICS.

WARNINGS

BEFORE THERAPY WITH CEFAZOLIN FOR INJECTION USP IS INSTITUTED, CAREFUL INQUIRY SHOULD BE MADE TO DETERMINE WHETHER THE PATIENT HAS HAD PREVIOUS HYPERSENSITIVITY REACTIONS TO CEFAZOLIN, CEPHALOSPORINS, PENICILLINS, OR OTHER DRUGS. IF THIS PRODUCT IS GIVEN TO PENICILLIN-SENSITIVE PATIENTS, CAUTION SHOULD BE EXERCISED BECAUSE CROSS- HYPERSENSITIVITY AMONG BETA-LACTAM ANTIBIOTICS HAS BEEN CLEARLY DOCUMENTED AND MAY OCCUR IN UP TO 10% OF PATIENTS WITH A HISTORY OF PENICILLIN ALLERGY.

IF AN ALLERGIC REACTION TO CEFAZOLIN OCCURS, DISCONTINUE TREATMENT WITH THE DRUG. SERIOUS ACUTE HYPERSENSITIVITY REACTIONS MAY REQUIRE TREATMENT WITH EPINEPHRINE AND OTHER EMERGENCY MEASURES, INCLUDING OXYGEN, IV FLUIDS, IV ANTIHISTAMINES, CORTICOSTEROIDS, PRESSOR AMINES, AND AIRWAY MANAGEMENT, AS CLINICALLY INDICATED.

Clostridium difficile associated diarrhea (CDAD) has been reported with the use of nearly all antibacterial agents, including Cefa