Yes, normal saline (0.9% NaCl) is compatible with cefazolin.
Cefazolin can be safely reconstituted, diluted, and administered with normal saline (0.9% sodium chloride) without precipitation or loss of stability. This compatibility is well-established across multiple authoritative sources.
Evidence from FDA Drug Label
The FDA-approved cefazolin drug label explicitly lists 0.9% sodium chloride (normal saline) as an appropriate diluent for both reconstitution and administration 1. The label specifies that for intravenous administration, reconstituted cefazolin can be further diluted in "Sodium Chloride Injection, USP" for intermittent or continuous infusion 1.
Evidence from Clinical Guidelines
The IDSA guidelines for catheter-related infections demonstrate practical compatibility by documenting cefazolin 5.0 mg/mL mixed with saline (as well as heparin) in antibiotic lock solutions, with explicit notation that "these antibiotic lock solutions will not precipitate at the given concentrations" 2. The guidelines also describe diluting vancomycin in 0.9% NaCl as part of preparation protocols, establishing normal saline as a standard diluent for cephalosporins in clinical practice 2.
Stability Data from Research
Multiple stability studies confirm this compatibility:
Cefazolin at concentrations of 10 mg/mL in normal saline remained stable for 72 hours at 8°C when mixed with metronidazole, with concentrations maintained at 98.4-101.0% of initial values 3
Cefazolin 1g in 100 mL of 0.9% NaCl maintained stability for 12 hours at room temperature when combined with clindamycin and gentamicin 4
Frozen solutions of cefazolin in normal saline retained >90% potency for up to 26 weeks when stored at -10°C or -20°C 5
Cefazolin diluted in normal saline and stored in polypropylene syringes or PVC bags retained at least 95.8% concentration after 30 days refrigerated and 91.8% after additional 72 hours at room temperature 6
Practical Considerations
- Normal saline is one of the preferred diluents for cefazolin across all routes of administration (IM, IV bolus, IV infusion)
- The solution remains clear with only slight yellowing over time, which does not indicate incompatibility 6
- No precipitation occurs when cefazolin is mixed with normal saline at clinically relevant concentrations
- Recent pharmacokinetic studies continue to use normal saline as the standard diluent for cefazolin administration, including for subcutaneous delivery 7, 8
In summary, normal saline is fully compatible with cefazolin and is one of the standard recommended diluents for its preparation and administration.