Bacteriostatic water (revision 1)
Old revision·09:00, 6 Jul 2024·DiffWatchDov
| Bacteriostatic water | |
|---|---|
| Composition | Water for injection with 0.9% benzyl alcohol |
| Function of the preservative | Inhibits microbial growth after entry |
| Contrast with | Sterile water for injection, unpreserved |
| Topic infobox · conventions | |
Bacteriostatic water is sterile water containing an antimicrobial preservative, conventionally benzyl alcohol at 0.9%. The preservative does not sterilise; it inhibits the growth of organisms introduced when a container is entered, which is what makes multiple withdrawals from one container possible. See Multi-dose vial.[1]
It is a diluent, not a treatment for non-sterile material. Adding it to a powder that was never sterile produces a non-sterile solution containing a preservative — the preservative retards growth of what is there rather than eliminating it.[2]
What the preservative does
[edit]Antimicrobial effectiveness is a defined pharmacopoeial property: a preserved preparation is challenged with specified organisms and must reduce their numbers by defined amounts over defined intervals. Benzyl alcohol meets that requirement over the concentration and pH ranges in which it is used.[1]
Inhibition is not immediate and not universal. Some organisms are more resistant than the challenge panel, and preservative efficacy falls with dilution — a preserved diluent added to a large volume of unpreserved liquid may fall below its effective concentration.