Cefazolin Drug Classification
Cefazolin is a first-generation cephalosporin antibiotic, which belongs to the beta-lactam class of antimicrobial agents. 1, 2
Chemical Structure and Classification
Cefazolin is chemically defined as 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, confirming its cephalosporin structure 2
As a semi-synthetic cephalosporin, it is formulated for parenteral (intravenous) administration only 2
Each gram of cefazolin sodium contains 48 mg of sodium 2
Pharmacological Properties
Cefazolin demonstrates a narrow spectrum of antimicrobial activity compared to broader-spectrum beta-lactams, making it less likely to select for resistant organisms 1
It achieves high intraamniotic concentrations when administered intravenously, which is clinically relevant for obstetric prophylaxis 1
The drug exhibits low minimum inhibitory concentrations (<0.5 µg/ml) against Group B Streptococcus and other susceptible organisms 1
Clinical Context and Positioning
Cefazolin is classified as a first-generation cephalosporin, distinguishing it from second-generation agents (such as cefoxitin, cefuroxime, cefamandole) and third-generation agents (such as ceftriaxone, ceftazidime) 1, 3
It is the preferred agent for surgical prophylaxis across multiple surgical disciplines according to major international guidelines, including recommendations from the American Society of Health-Systems Pharmacists, IDSA, and WHO 3
The drug possesses a unique R1 side chain structure that differs from all penicillins and other cephalosporins, which has important implications for cross-reactivity patterns in allergic patients 4
Resistance Profile
Cefazolin demonstrates stability against many beta-lactamases, though it shows variable activity against organisms producing cephalosporinases 5
It maintains strong antibacterial activity against gram-positive bacteria, particularly Staphylococcus aureus, with more than 90% of strains suppressed at concentrations of 3.13 µg/ml or less 6
Among first-generation cephalosporins, cefazolin shows superior activity against gram-negative pathogens including Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis 6