Sterile Alcohol

• Production items passing into a cleanroom area such as trolleys and equipment are subject to a decontamination transfer process. Where items cannot reasonable be treated by autoclaving or irradiation, then chemical ( alcohol ) disinfection is the leading choice.
• Within the cleanroom, rapid decontamination of workbenches, production equipment and items such as gloved hands is required. This can be during operations, between set time intervals, at shift hand-overs, and between batches, wherever a rapid 'no rinse-down' process is needed.

Alcohol like any other disinfectant is only effective when applied correctly. There are several application modes for water/alcohol mixtures that are suitable for cleanrooms:-

• Spraying - Probably the most popular due to the ease of application - the fact that horizontal and vertical surfaces may be easily contacted. There are two major 'off-the-shelf' designs in existence : trigger sprays and nitrogen pressure aerosols. There are features of each which lend themselves to use in cleanrooms, but due to the totally sealed form of the nitrogen pressure aerosol it is better suited to class A & B ( class 100 ) areas and isolators, whilst the trigger spray is more suitable for lower specification cleanroom areas. The underlying reason for this becomes evident when qualification of 'period of use' is undertaken. Period of use is the time an opened product should be utilised in the cleanroom, with multiple threaded connections and the possibility of aspiration back in the container the trigger spray device has to take a second place to crimped, sealed and permanently pressured aerosol device. For large scale applications, specialised sanitary designed autoclavable spray units can be employed.

• Wiping-Utilising either impregnated wipes or a wipe in conjunction with a spray device, wiping offers much in the way of contamination control. Clearly there is a mechanical cleaning benefit where the wipe material captures hard particles and biological material and the alcohol's presence only plays a small part. The other advantage is that the alcohol solution is confined to a discreet area i.e. no 'over-spraying' onto surfaces not intended to be contacted or in the case of particle counters no false alarms during the cleandown process.

• Fogging ( wet misting ) - this can be viewed as a much larger scale version of an aerosol. Taking the form of a reservoir which has a nebuliser attached to a blower fan, these units are capable of producing a fine mist, but also capable of projecting the mist across a large distance. Given a large enough reservoir whole areas can be treated with ease. The relative downside is that of cleanroom introduction as the equipment is not autoclavable nor able to withstand gamma irradiation.
• Immersion- As simple as it sounds, if an item is suitably sized and compatible, then full immersion for the validated contact time is an ideal way to ensure total contact. As with most methods due consideration must be given to ensure that items are disinfected in a sequence ( cleanest first ), which minimises the risk of cross-contamination.
• Mopping- when faced with large areas of floor to disinfect, mopping may be the only economic way forward. As this may involve large amounts of alcohol, safety becomes of importance. There should not be any naked flame or incandescent materials present e.g. ampoule sealers. One should also look at air change rates to satisfy both the requirements of contact time, and the respiratory safety of the operator(s)

In this context of critical area contamination control, the "alcohol" in alcohol solutions in water is widely accepted to mean either Isopropyl Alcohol ( IPA ) or denatured Ethanol. Both are inedible, and have very similar safety and efficacy profiles. In general IPA is easier to define in terms of purity and is most cleanroom users choice. In the UK, denatured ethanol is defined as 19 volumes of ethanol with I volume of approved wood naptha. Wood naptha's main constituent is Methanol, but also contains other alcohols and pyridines and impurities designed primarily to render the whole solution inedible, and to make illicit attempts at separation of the ethanol component very difficult. Wood naptha is not the only denaturant in use, each EC member has a standard for denatured ethanol, some do not lend themselves to cleanroom usage - residues on evaporation would be too high. Other denaturants such as Denatonium benzoate show a way forward to a well defined version of denatured ethanol which is much more suited to cleanroom applications. Denatonium benzoate otherwise known as Bitrex™ is recognised as the bitterest substance known to man and easily renders ethanol wholly unpalatable.

Broadly effective against bacteria it is generally accepted that the key mode of action of alcohol on bacteria is one of protein denaturation. When water is present protein denaturation occurs more readily. Interference with microbial metabolic processes is also well documented, and is responsible for the inhibition of spore germination, this is a reversible process - when alcohol is removed from the spore's environment, germination can take place ( Trujillo & Laible 1970 ) Under the correct conditions alcohol solutions can also induce bacterial cell lysis.

Alcohol solutions are also effective against viruses, work by Klein & Deforest (1963) showed inactivation against all seven general virus types, alcohol solutions are also effective against many Fungal species - Kruse et al (1963,1964)

Clearly then the argument for the use of alcohols in controlling cleanroom micro-organisms is a strong one. As solutions, which have not been irradiated or sterile filtered, could potentially contain bacterial spores, sterilisation prior to use is required. As per the GMP guidelines this is an expectation in class A & B cleanrooms, but clearly it is a good practice in any classification of cleanroom.

Studies from as long ago the 1900's showed that alcohol's efficacy is optimised at a 70% with water. The water content is important for effective protein denaturation, and kill times, which are practical, but will any diluent water quality be sufficient for critical cleanroom use? In the aforementioned PDA survey, water for Injection (WFI) was also recognised as being the most frequently used diluent to alcohol. The logic behind this selection is one of risk assessment, specifically concerning endotoxin presence. With a specification of 0.25 EU ml ^_1 the use of WFI effectively enables management of endotoxin levels in the final product. Anything less than a sterile formulation of 70 per cent alcohol made in WFI can create a 'contamination control paradox' in which the product used to control contamination, can actually contribute to the risk by introducing endotoxins ( if WFI is not used ) - of strong interest to parenteral facilities , or introduce micro organisms - of interest to all cleanroom owners.

Sterilisation of alcohol solutions is achieved typically by one of two processes:-

Aseptic - Sterilising filtration.

Terminal - Gamma irradiation

The aseptic route is the one taken by most in-house operations as the equipment and skill sets are usually to hand. The economics of this route can be highly variable, the 'cost per litre' will vary by batch size and batch expiratory times. The real underlying cost of manufacturing this aseptically prepared disinfectant is much higher, as manufacture, testing and documentation for even a day's worth of disinfectant may comprise of :

• Batch chemical analysis
• Change Control
• Documentation and batch numbering of all raw materials and packaging components
• Audit and approval of suppliers
• Pre-sterilisation of packaging i.e. spray bottles
• integrity testing of all filters; Pre and Post filling
• Pre-filtration of raw materials and finished solution
• Sterilising filtration (0.2 micron)
• Aseptically fill/manipulation
• WFI water and 0.2 micro filter costs
• Sterility test and endotoxin analysis of finished product
• Validation of all parts of the production process
• Compilation of batch documentation

• Validation shelf life and in-use shelf life

Large scale manufacture by disinfectant suppliers to the pharmaceutical industry can make this an efficient process based upon the economies afforded by scale and terminal sterilisation by Gamma Irradiation. This process ensures that the liquid (internal) portion of the product is sterile, but just as importantly that the external surface of the product is also rendered sterile. This coupled with a suitably well controlled 'double bagging' process prior to irradiation provides end users with a simple transfer procedure. That is to say, transferring the packaged item into the cleanroom is simply a question of removal of the layers in a sequential manner to finally allow entry to the class A or B ( class 100 ) core without introducing externally borne micro-organisms.

The process of gamma irradiation then is the next port of call for cleanroom users to assure themselves that the out-sourced disinfectant is capable of being provided consistently sterile.

The "degree of sterilisation" (sterility assurance level or SAL) is directly related to the amount of ionising radiation absorbed by the material. There must be sufficient energy to kill micro-organisms, but not too much so that there are unacceptable material alterations.

In practice, not all parts of the products receive exactly the same radiation dose with density, thickness, and geometry differences all playing a part.

The Association for the Advancement of Medical Instrumentation (AAMI) has developed procedures to allow determination of a radiation dose capable of delivering a specified level of sterility. This is based on product end-use and bioburden, instead of requiring one fixed dose for all. AAMI dose setting methods have now been included in the international ISO 11137 standard for validating radiation processes. Quarterly dose audits are required to verify the validity of the sterilising dose selected. The pharmaceutical end-user should care should ensure the out-sourced irradiation process is not being used as a terminal sterilising "catch-all" to mask a high bioburden production process.

Many disinfectant suppliers are seen as meeting the pharmaceutical and regulatory needs for economic out-sourcing of this product type. Out-sourcing of such an item/service should of course to follow the route of establishing that the supplier is audited, ensuring a consistent GMP process is in evidence and product specifications are set.

One would expect that all sterile disinfectant manufacturers would follow a similar route of documentation and quality to the 'small scale' in-house route, with due alteration to include gamma irradiation, that is to say a well controlled GMP process.

Currently this is not the case, there are few such GMP disinfectant suppliers, but a plethora of sterile disinfectant manufacturers. Validatability is the key factor the pharmaceutical industry should be looking for in an out-sourced situation such as this. There is nothing more frustrating to select a disinfectant, start the process of validation, at which time specifications and tolerances are set, only to find further down the line that product variability and inconsistencies of control are encountered. An earlier vendor audit and the security of a GMP process would have saved much in time and cost. Thus before the product is focussed upon, in terms of chemistry, compatibility and efficacy, the first questions should always surround how consistent and therefore validatable the product is.

Quality of documentation is of course of key importance. A typical real-world example of this is the presence / absence of a customer notification programme. This is where minor to major alterations in product or manufacturing processes are formally announced to users, with supporting equivalency data. This is done ahead of the changes happening, to allow users to evaluate the change and its importance or not to them, and if any additional work is required, the advance notice ensures that this can be done whilst existing product stocks exist.

Essentially, seeking to out-source this type of product or any other disinfectant intended for a GMP environment is a thoroughly logical step for the pharmaceutical and medical device industry. The biggest challenge facing the industry is to rationalise the order of events leading up to out-sourcing, in the case of disinfectants much emphasis is placed on either product specification or price. Without review of the ability of the supplier to provide product consistently and under GMP, the product that is ultimately 'validated' on site may not be, that validation pertained to a specification, which has now been altered with no customer involvement. What is the real cost then?