Water For Injection: USP, EP Specs, Production and Pharma Uses

Water for Injection (WFI) is an important part of the pharmaceutical industry, used in the production and packaging of parenteral medications.

We’ll start by explaining what water for injection is, how it differs from other types of water, and why it’s important in pharmaceutical manufacturing. We then delve into the various methods used to produce WFI, including distillation, reverse osmosis, and membrane filtration.

What is water for injection?

Water for injection referred to as WFI, is a kind of drug dilution solvent, which is mainly used to dilute the drugs and solutions injected into the body. Global Pharmacopoeia also defines it as a water quality standard.

Water for injection is free of bacterial endotoxin and is one pharmaceutical-grade pyrogen-free water. It is frequently used in the intravenous administration of drugs, especially in the intravenous administration of drugs that need to be in direct contact with the patient’s blood.

Water for injection is critically important in the pharmaceutical product and application industry, involving the mandatory use of injectable drugs, blood filtration, active pharmaceutical ingredient production, and many other applications.

Types of Water For Injection

Drugs for injection are created using a solvent called water for injection. Water for injection can be utilized in bulk pharmaceutical chemical (BPC) or bulk active pharmaceutical ingredient (API) preparations as a final cleaning rinse agent.

USP WFI

USP WFI is the component used to create sterile and bacteriostatic WFI. Since it is not the final product, considerable validation is required to make sure it complies with USP standards.

USP Bacteriostatic WFI

USP Bacteriostatic WFI is sterile water with added benzyl alcohol (0.9%), which acts as a preservative. Antimicrobial WFI extends the life of the water bottle to up to 28 days for repeated use.

USP Sterile WFI

USP Sterile Water for Injection is required in single-use vials and then applied for intravenous administration. It cannot be used again after being heated or opened and must be thrown away.

WFI Specifications: USP, EP, and JP Standards

The three major pharmacopoeias set legally binding quality limits for WFI. The specifications are largely harmonised across USP, EP, and JP, with the main practical difference being accepted production methods.

The 2017 EP revision – membrane methods now accepted

Prior to April 2017, the European Pharmacopoeia required distillation as the sole production method for WFI. The revised Ph. Eur. Monograph 0169, effective 1 April 2017, expanded accepted methods to include purification processes equivalent or superior to distillation in the removal of chemicals and microorganisms, most commonly reverse osmosis combined with electrodeionisation and ultrafiltration. This change brought the EP into closer alignment with the USP, which has always permitted methods equivalent or superior to distillation. The Japanese Pharmacopoeia has made a similar revision.

This regulatory change is significant for facilities evaluating WFI system upgrades or new installations: ambient membrane-based systems are now a compliant option globally, with the exception of China, whose pharmacopoeia continues to require distillation only.

Comparison of water for injection and pure water

Purified water is pure water without minerals or by-products and contains only hydrogen and oxygen. Purified water is mechanically filtered to remove all impurities for use, and distilled water is one of the most typical types of purified water.

Water for injection is part of the purified water system used by the pharmaceutical sector. WFI serves as an excipient in the manufacture of injection goods to regulate the presence of additives like endotoxin. It also can clean the parenteral product containers.

In order to preserve its qualities, water for injection is condensed and stored at a temperature of 80 to 90 degrees Celsius. The desired amount of solute is added, and it is then kept in a single dose for Iv delivery. In contrast, purified water only needs to be kept at room temperature.

The main different point is that the purified water is kept at ambient temperature while the WFI is maintained at an 80–90°C temperature. This actually means that the temperature of the WFI needs to be heated and maintained using a recirculating heat exchanger, while the temperature of the PW needs to be cooled and heated.

Method for preparing WFI

The process of producing water for injection has traditionally involved distillation. With the diversification of technological development, the generation method of water for injection will also choose reverse osmosis according to specific requirements. The goals of both are the same, and all use pure water for further processing to meet the use standards of WFI.

The distillation process of water for injection includes two types of multi-effect distillation and vapor compression distillation, both of which are WFI (water for injection) processes approved by pharmaceutical institutions. It can also be produced via a reverse osmosis system with a downstream ultrafiltration unit.

Vapor Compression Distillation

Vapor compression distillation, also known as thermal compression, or mechanical vapor compression, is fundamentally comparable to the evaporation system technology used for seawater desalination.

Vapor compression (VC) distillation systems are powered by steam or electric heating, operate at relatively low temperatures, and have minimal requirements for feed water quality. The VC distillation system uses a compressor and other moving parts to compress the steam while increasing its evaporation pressure and temperature.

Multiple Effect Distillation

Multiple effect distillation(ME)systems are very common methods used to produce water for injection. The uniqueness of the multi-effect still is its multi-column design, which helps to reuse the steam energy throughout the operation and does not require too many moving parts, only cooling water to handle the final distillation of the production process.

The multi-effect distillation system needs to absorb a lot of energy and cooling water to obtain water for injection. When the required capacity is not too much or the budget is limited, it is a good choice to switch to a single-effect still to produce water for injection.

Reverse Osmosis (RO) System + Ultrafiltration (UF)

As we all know, the quality of the water supply is directly related to the technical process of producing water for injection. Only when the water quality is extremely good, the reverse osmosis system is the first choice for producing water for production.

The most important point of this system is to install an ultrafiltration device in the downstream position for pretreatment, the purpose is to change the quality of the influent water so as to produce cold WFI. Pretreatment technology involves various methods such as water softening, descaling, prefiltration, nanofiltration, ultraviolet treatment, and microfiltration.

Unlike stills, RO systems require continuous control of their efficiency in terms of membrane degradation, biofilm prevention, and microbial load when put into production use, as well as periodic disinfection and validation. The real advantage of reverse osmosis is that it reduces energy demand and waste.

Why Purity Matters for WFI

Every step of WFI production is designed to ensure that the final liquid is free from bacteria and organic carbon contamination. Its production specification is more stringent than that of pure water production specification.

The standards stipulated by the United States Pharmacopoeia require that the aerobic bacteria per 100ml should not exceed 10 CRU, the total organic carbon should not exceed 500ppm, and the endotoxin per milliliter should not exceed 0.25EU. The products produced in this way are up to the standard and available for use.

It is crucial to adhere to these stringent procedures since they reduce the possibility of contamination. Any bacteria or other organic substances that get into the final preparations may increase the risk of infections in patients or decrease the effectiveness of the medications being created.

Filtration in WFI Production and Pharmaceutical Water Systems

Filtration plays a critical role at multiple stages of WFI production and use, regardless of whether distillation or membrane-based generation is employed.

Pre-treatment filtration protects the WFI still or membrane system from suspended solids, chlorine, and organic compounds in the feed water. A typical pre-treatment train includes sediment depth filtration, activated carbon, and water softening before the primary purification stage. The feed water quality directly affects the life of membranes and the performance of distillation equipment.

Membrane filtration in ambient WFI systems: The ultrafiltration membrane at the final stage of an ambient WFI system provides validated endotoxin reduction, typically achieving a 4-log reduction in endotoxin concentration. The UF membrane is the critical bioburden control step in ambient systems, equivalent to the role that boiling plays in distillation.

Sterilising filtration at point of use: Where WFI is used to prepare injectable drug formulations, a 0.22 micron sterilising-grade membrane filter provides the final bioburden reduction step before filling. This step is performed under aseptic conditions and uses absolute-rated membrane cartridges validated for bacterial retention.

Filter integrity testing: sterilising-grade filter cartridges used in WFI handling and injectable drug preparation must pass integrity testing before and after each use. Integrity testing — bubble point test or diffusion flow test, confirms the membrane is intact and performing to its validated specification. A filter that fails post-use integrity testing triggers a batch investigation.

View Brother Filtration filter integrity testing guidance →

Conclusion

Water is a universal solvent and has long been crucial in the pharmaceutical industry’s medication manufacturing process. An essential component in the creation of biopharmaceuticals is water for injection. The best option can be chosen among the three manufacturing processes: membrane-based reverse osmosis, vapor compression distillation, and multi-effect distillation depending on the end-use requirements and production capacity.

Brother Filtration can help you identify the most suitable potential options for your water treatment in the pharmaceutical industry, based on the membrane-based reverse osmosis process. Our professional water treatment and filtration process can help you implement a higher standard process to achieve your water for injection production goals.

FAQs About Water For Injection

What is water for injection used for?

WFI is used as a solvent and diluent in the preparation of injectable drug products, as a final rinse for equipment and containers that contact injectable formulations, and in bioprocessing where endotoxin control is required. Because it enters the bloodstream directly, it must meet stricter purity standards than any other pharmaceutical water grade.

What is the difference between WFI and purified water?

The key difference is the endotoxin requirement. WFI must contain not more than 0.25 EU/mL of bacterial endotoxins and not more than 10 CFU/100 mL of microorganisms. Purified water has no compendial endotoxin limit and a higher microbial limit of 100 CFU/mL, making it unsuitable for injectable drug manufacturing.

What is the storage temperature for water for injection?

WFI is stored and circulated at either above 80°C in a continuously recirculating hot loop, or below 4°C in a cold loop. The 80°C hot loop is the standard approach in most facilities, the elevated temperature prevents microbial growth in the distribution pipework without chemical sanitisation.

What is the difference between WFI and sterile water for injection?

WFI is a bulk water grade produced and distributed continuously through a validated facility loop. Sterile water for injection is WFI filled into single-dose containers of maximum 1 litre and terminally sterilised. Both meet the same chemical and endotoxin specifications. The difference is form, WFI is a bulk manufacturing material, sterile water for injection is a packaged single-use diluent.