Most Prescribed First-Generation Cephalosporins in Canada
The most commonly prescribed first-generation cephalosporins in Canada are cephalexin (oral) and cefazolin (intravenous), with cefadroxil serving as an alternative oral option.
Oral First-Generation Cephalosporins
The primary oral first-generation cephalosporins used in Canadian practice include:
Cephalexin is the most frequently prescribed oral first-generation cephalosporin, typically dosed at 500 mg every 6 hours 1. It is widely used for skin and soft tissue infections, urinary tract infections, and as step-down therapy from intravenous antibiotics 1.
Cefadroxil serves as an alternative oral agent, dosed at 500 mg every 12 hours, offering the advantage of less frequent dosing compared to cephalexin 1. Recent evidence demonstrates that cefadroxil and cephalexin have equivalent MIC distributions (MIC50 of 2 μg/mL and MIC90 of 4 μg/mL) against methicillin-susceptible Staphylococcus aureus 2.
Cephradine is occasionally used at 500 mg every 6 hours, though it is less commonly prescribed than cephalexin or cefadroxil 1.
Intravenous First-Generation Cephalosporin
- Cefazolin is the predominant parenteral first-generation cephalosporin, typically dosed at 1 gram every 8 hours 1. It is the antibiotic of choice for surgical prophylaxis across multiple procedures including urological, gastrointestinal, and orthopedic surgeries 1. Cefazolin has a unique side chain structure that results in very low cross-reactivity with penicillins, making it particularly useful in patients with penicillin allergies 1.
Clinical Context
First-generation cephalosporins remain the most potent agents against gram-positive organisms, particularly Staphylococcus aureus and Streptococcus species, though they have limited activity against gram-negative bacteria compared to later-generation agents 3, 4. They are indicated for surgical prophylaxis and treatment of most staphylococcal and streptococcal infections in patients allergic to penicillins 4.
Important caveat: First-generation cephalosporins have poor coverage for Haemophilus influenzae and are inappropriate for infections where this pathogen is suspected 1. They also lack activity against enterococci, Bacteroides fragilis, and Pseudomonas aeruginosa 4.