CEFAZOLIN- cefazolin sodium injection, powder, for solution
West-Ward Pharmaceutical Corp



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


Cefazolin for Injection, USP is a semi-synthetic cephalosporin for parenteral administration. It is the sodium salt of (6R, 7R)-3-[[(5-methyl-1,3,4-thiadiazol-2-yl)]thio]methyl]-8-oxo-7-[2(1H-tetrazol-1-yl)acetoamido]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid.

The structural formula is as follows:

Cef Chemical Structure
(click image for full-size original)

Cefazolin for Injection, USP is a white to cream sterile powder. The color of Cefazolin for Injection, USP solutions may range from pale yellow to yellow without a change in potency.

The pH ranges from 4.0 and 6.0 for a solution containing 100 mg of cefazolin per mL.

Cefazolin for Injection, USP is supplied in 10 or 20 grams Pharmacy Bulk Packages. Each Pharmacy Bulk Package contains Cefazolin Sodium, USP equivalent to 10 or 20 grams of cefazolin. The sodium content is approximately 48 mg (2.1 mEq) per gram of cefazolin sodium. It is to be administered by intravenous route.

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. FURTHER DILUTION IS REQUIRED BEFORE USE.


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 1 gram dose.

The serum half-life for cefazolin is approximately 1.8 hours following intravenous 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 level at the third hour of approximately 28 mcg/mL.

Studies in patients hospitalized with infections indicate that cefazolin produces mean peak serum levels 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, AST (SGOT), ALT (SGPT), bilirubin, alkaline phosphatase, BUN, creatinine and urinalysis, indicated no clinically significant changes attributed to cefazolin.


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 the INDICATIONS AND USAGE.

Gram-positive Aerobes
Staphylococcus aureus (including beta-lactamase producing strains)
Staphylococcus epidermidis
Streptococcus pyogenes, Streptococcus agalactiae, and other strains of streptotocci
Streptococcus pneumoniae
Methicillin-resistant staphylococci are uniformly resistant to cefazolin, and many strains of enterococci are resistant.

Gram-negative Aerobes
Escherichia coli
Proteus mirabilisMost strains of indole positive Proteus (Proteus vulgaris), Enterobacter spp., Morganella morganii, Providencia rettgeri, Serratia spp., 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:


Zone Diameter (mm)


≥ 18

15 – 17


Susceptible (S)

Intermediate (I)

Resistant (R)

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 drug can be used. This category also provides a buffer zone that prevents small uncontrolled technical factors from 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:


Zone diameter (mm)

E. coli ATCC 25922

S. aureus ATCC 25923

21 – 27

29 – 35

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:

MIC (mcg/mL)


≤ 16

≥ 64

Susceptible (S)

Resistant (R)

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:


MIC (mcg/mL)

S. aureus ATCC 25923

E. coli ATCC 25922

0.25 – 1

1 – 4

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