Bacteriostatic water and sterile water: the difference

The pharmaceutical figures below are from two Hospira labels, for Sterile Water for Injection, USP and Bacteriostatic Water for Injection, USP, the names used in the United States Pharmacopeia.

A bacteriostatic agent stops bacteria from multiplying; a bactericidal agent kills them. Benzyl alcohol at this strength is the first kind. It does not sterilise the water, which is sterile already when the vial is sealed, and it does not make a contaminated vial clean. Its job is narrower: once a stopper has been pierced, any bacteria that get in are held back between one withdrawal and the next.

That is why the two waters come in different containers. With nothing to hold bacteria back, sterile water for injection is packed for one use and the rest thrown away. Bacteriostatic water is packed for repeated withdrawals from the same vial.

Cosmetic formulators in Egypt will know it from another place. Benzyl alcohol is a permitted preservative under the EU Cosmetics Regulation, Annex V entry 34, at up to 1.0% in a finished product. The Egyptian Drug Authority (EDA) names the European cosmetic requirements among the rules in its cosmetic registration guide.

Sterile water for injection is made and labelled as a medicine: the labels quoted above are drug labels, and both describe the water as sterile and nonpyrogenic. In Egypt, medicines are registered with the EDA and sold through licensed pharmacies. The EDA's drug database, on edaegypt.gov.eg, can be searched by trade name, generic name or registration number to check a particular pack.

Bacteriostatic water is sold under different labels by different suppliers. Ours is a laboratory diluent: 3 ml vials of water with 0.9% benzyl alcohol, labelled for research use only. It is supplied to laboratories and businesses we have verified. It is not a medicine, it is not labelled for use in people or animals, and it is not a substitute for a registered medicine.

The two Hospira labels give the same condition: 20 to 25 °C, the United States Pharmacopeia's controlled room temperature. Neither needs a fridge before opening. For an opened vial, follow what that product's label and its supplier say, not a general rule.

Room temperature in Egypt is not 20 to 25 °C for much of the year. A summer store room in Cairo or Upper Egypt, or a vehicle, can be well above that range. Keep stock indoors in a cool place, and move deliveries out of the heat as soon as they arrive. Peptide storage and handling covers laboratory practice for the materials these waters are used with.

• Sterile water for injection, for a patient: a licensed pharmacy or a hospital's own supply. We do not supply it.
• Bacteriostatic water, for a laboratory: suppliers of laboratory materials. We supply it to businesses and institutions in Egypt that pass our checks, and we deliver to your business address in Egypt. We do not supply individuals. Bacteriostatic water, 3 ml vials has the product details, and who can buy from us lists the checks.