Preparation
Sterile water
Sterile water for injection, when it is the right diluent, and why it is not interchangeable with bacteriostatic water.
- Last updated:
- 2026-07-22
Overview
Sterile water for injection is water that has been filtered, sterilised, and packaged for injection. It contains no preservative. Because there is no preservative, its intended use is single-dose: once opened, any unused portion is discarded.
It is the diluent of choice where a preservative would be inappropriate (specific patient populations, specific formulations) or where the reconstituted solution is used within a single working session.
Why it matters
Choosing between sterile water and bacteriostatic water is not a matter of preference. The two diluents produce different downstream considerations for storage, in-use time, and applicable contraindications.
Key concepts
No preservative
Sterile water for injection contains no benzyl alcohol or other antimicrobial preservative. Microbial growth is only limited by the absence of nutrients, not by an active agent.
Single-dose intent
The product is packaged for one use per vial. Repeated access to a sterile-water vial defeats its intended sterility assurance.
Not for direct injection alone
Sterile water alone is not isotonic. It is a reconstitution or dilution diluent for other products; injecting pure water intravenously is a distinct medical error with its own risks.
Common misconceptions
- "Sterile water is stronger than bacteriostatic water." They are different products for different use patterns.
- "Sterile water and bacteriostatic water are interchangeable." They are not. The presence or absence of preservative changes the downstream in-use time and the applicable contraindications.
- "Distilled water is sterile water." No. Distillation is a purification process; sterility is a separate specification.
Practical interpretation
Use sterile water where the compound page or the practitioner reference specifies it, typically in single-session reconstitutions. Do not substitute bacteriostatic water without understanding what the preservative changes.
Limitations
Diluent choice is documented on the compound page for information; it is not a recommendation to prepare or administer any compound.