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Published on 1 April 2003

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Pharmaceutical isolator design: access devices

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Brian Midcalf
BPharm FRPharmS
Pharmaceutical
Consultant
Assistant PTQA
Course Director
School of Continuing Education
University of Leeds
UK

The generic term “access device” is used to describe the mechanical means by which manipulative work is carried out within an isolator. The access device is normally used by a
human operator and is specifically designed to avoid breaking the containment while manipulations are carried out. In some cases the work may be carried out by a robot.

It is important to select the most appropriate access for the type of work involved. The position and mounting of access devices is also largely dictated by the ergonomics of the work to be carried out. There are a number of considerations to be made in relation to the operator interface with the working procedures, and these are discussed below. A single solution is not practical for all applications, and each should be considered on its own merit.

Gloves
Gloves will usually form the distal end of the access device. It should be clearly understood that gloves usually represent the most vulnerable part of the isolator barrier system. There are a number of important points that should be considered (see Table 1).

[[HPE08_table1_11]]

A number of compromises will need to be made when choosing gloves, such as balancing operator dexterity against glove strength. The following variables may have a bearing on the choice of glove:

  • Glove type.
  • Glove material.
  • Type of operation.
  • Testing and maintenance.
  • Need for product protection.
  • Need for operator protection.
  • Ergonomics and operator comfort.
  • Operational environment (solvents, moisture, heat).
  • Chemical compatibility (gas-sanitising agents).
  • Overall durability.
  • Need for touch sensitivity.
  • Cost and cost-effective quality.
  • Cleanability
  • Single (named) or multiple operator use.
  • Electrostatic properties.
  • Detection of leaks.

It is possible to provide a summary comment only on some of these factors:

Glove type
The choice here is between handed gloves and ambidextrous gloves. The cuff design of some isolator manufacturers will dictate that a certain type of glove is used. This could mean that a bead-ring at the wrist is a requirement.

Glove material
Gloves are available in a wide variety of materials, and the properties of these should be understood. Gloves have been made from natural rubber latex, neoprene, nitrile, “Hypalon”, butyl, “Viton” and EPDM (ethylene propylene). Information about some of these and other materials is provided in EN/ISO 14644 – Part 7.

It is not unreasonable to expect manufacturers to supply test data on their gloves, but it may be necessary to perform additional testing to determine the most suitable material for a particular process application. Gloves are produced by a dipping process using hand-shaped formers into a liquified material. The size of the glove is determined by the size of the former. The thickness of the glove is built up by repeated dipping until the required thickness is achieved. It is also possible to produce gloves of dual thickness, thicker around the perimeter and thinner on the finger or palm zones, to enhance touch sensitivity. A further variation is glove production as a laminate combining the different properties of two or even more materials.An example is Hypalon and neoprene, which combines the flexibility of neoprene with the ozone and chemical protection of Hypalon; another example would be the incorporation of lead – “leadloaded” – to provide radiation protection.

Additional considerations

Allergic reactions
Natural latex rubbers contain proteins that are capable of producing an allergic reaction in some operators. This is best avoided by specifying good-quality gloves with low allergen content or by wearing inner gloves of a different material.

Quality
As gloves form the critical barrier between operator and products, it is of prime importance to use gloves that do not leak. Users should satisfy themselves about the quality and leak tightness of the product they are using. It is also important that gloves are tested for leak tightness.

As gloves are used in the controlled workspace of an isolator they need to be nonshedding of particulates, particularly when used in aseptic applications. This is a good reason for using powder-free gloves. Gloves for use in isolators for aseptic work should normally be supplied in a sterile state and suitably packaged. It is also possible for gloves to be treated in situ as part of the sanitisation or sporicidal gassing process of the isolator. The shelf-life and “in-house” stock rotational procedures are inherently important control factors to ensure old and possibly degraded gloves are not used.

Cytotoxic (antineoplastic) drug manipulation
Special considerations are needed for handling cytotoxics. Studies have shown that cytotoxic solutions pass through virtually all glove materials given time. For this reason, gloves should be changed regularly and consideration should also be given to double-gloving.

Gauntlets
A gauntlet is effectively a one-piece sleeve and glove
combined. They may be full or mid-arm length. In general they are not as sensitive in use as “surgicaltype” gloves and are generally used in more arduous or intensive procedures. They are particularly suitable for hazardous containment situations and can be produced in many materials, including laminates and radiation-protecting materials.

More than one operator often uses them. Consideration should be given to hygiene requirements. An acceptable way of operating involves the use of liner gloves, which are available in a range of sizes.

Cuff rings
These are normally mouldings or machined plastic, with grooves to retain the o-rings of the sleeve, the glove-bead, and suitable security o-rings, depending on the design. They should be as light and unobtrusive as possible, but strong enough to withstand the glove-change process.

Conclusion
Isolator technologies are used in a wide range of specialised procedures and are therefore available in a wide range of different configurations, as discussed in the first article in this series. This article described the range of gloves, gauntlets and cuff rings available for allowing the operator access to materials within the isolator without disrupting their containment. The next article of this series will discuss isolator leaks – how best to quantify them and the risks they pose.

Acknowledgment
The author is indebted to the Pharmaceutical Isolator Working Party for information relating to developing the new guide. A synopsis of part of this is represented in this article.

Resource
Pharmaceutical
Isolator User Group
W:www.piug.org.uk
Contact:
Samantha Armitage
Professional Lifelong Learning Unit
School of Continuing Education
University of Leeds
Continuing
Education Building
Springfield Mount
Leeds LS2 9NG
UK
T:+44 (0)113 343 3236/3241
F:+44 (0)113 343 3240

Event
7th Pharmaceutical
Isolator Conference
In association with the Parenteral Society
Cairn Hotel
Harrogate, UK
11–14 May 2003

Further reading
Lee MG, Midcalf B, editors. Isolators for pharmaceutical
applications.
London: HMSO;1994



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