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High-Level Disinfectants

Disinfection and sterilization are required to prevent medical and surgical instruments from transmitting infectious pathogens to patients. Patient care items and equipment are classified into categories of critical, semicritical, and noncritical. Critical items come into contact with sterile tissue or the vascular system. Semicritical items come into contact with mucous membranes or non-intact skin. Examples of semicritical items are some endoscopes and diaphragm fitting rings. Noncritical items contact with the skin, but not the mucous membranes. Examples of noncritical items are stethoscopes, bed rails, over bed tables.

Since several important pieces of medical equipment and surgical equipment, such as endoscopes, cannot be sterilized by heat. Cold disinfectants (high-level disinfectants) are an essential part of the disinfection process. High-level disinfectants are used to disinfect the items to prevent the item from potentially infecting another patient.

According to the CDC, high-level disinfection is normally defined as complete elimination of all microorganisms in or on an instrument, except for small numbers of bacterial spores. The FDA definition of high-level disinfection is a sterilant used for a shorter contact time to achieve a 6-log10 kill of an appropriate Mycobacterium species. The CDC also states that cleaning followed by high-level disinfection should eliminate enough pathogens to prevent transmission of infection.

Test Strips are required to test the high-level disinfectant solutions to ensure they can efficiently destroy microorganisms. The test strips measure the minimum effective concentration (MEC) required for high-level disinfection. High-level disinfectants need to be tested prior to every use to ensure the minimum effective concentration (MEC) meets the manufacturer’s requirement. The test strips are generally specific to the product and they are sold separately.

As with many other types of purchases, choosing which type of high-level disinfectant to use can be challenging. With limited budgets and other considerations, such as the long-term effects of the products we use, it’s important to feel comfortable with the choices we make. When looking at disinfectants for medical equipment, this means evaluating their effectiveness, ease of use, and safety.

For manual processing, medical facilities use disinfectant containers such as the CIDEX Rectangle Instrument Tray.

OPA and the Food and Drug Administration (FDA)

Prior to 1999, glutaraldehyde solutions were widely used as high-level disinfectants and they continue to be used for high-level disinfection. In October 1999 the Food and Drug Administration (FDA) approved the use of ortho-phthalaldehyde for use as a high-level disinfectant. The FDA approved ortho-phthalaldehyde because studies found “excellent microbiocidal activity in in vitro studies.” According to an article at the Centers for Disease Control and Prevention. Ortho-phthalaldehyde eliminated several microorganisms, such as mycobacateria and Bacillus subtilis spores, which were found to be resistant to glutaraldehyde, they reported. Since ortho-phthaldehyde (OPA) was approved by the FDA it was quickly adopted and used in medical facilities all over the world.

Ease of Use

As with all disinfection processes, used or contaminated equipment must first be thoroughly cleaned with a protein-dissolving detergent, and all debris removed. Once excess water has been drained and the equipment is dry, the equipment can be placed in a high-level disinfectant solution and soaked according to sterilization protocols. Many high-level disinfectants are ready to use solutions. Some high-level disinfectants require activation, mixing, or dilution. OPA solutions are ready to use.

Ease of Disposal

Many high-level disinfectants may be disposed of as domestic waste in many states. However, please confirm how to dispose the specific solution being used with both state laws and facility protocols to ensure proper and legal disposal.


Precautions are always necessary when working with equipment disinfectants. OPA solutions are preferred in many situations because they are virtually odorless. Additionally, most OPA-based high level disinfectants do not appear to cause irritation to the eyes or nasal passages and they do not require special venting or room air monitoring. Proper gowns, gloves, and goggles should be worn while handling high-level disinfectants and the equipment that has soaked in it.

Monitoring the MEC

Test Strips are required to test high-level disinfectants before they are used to ensure they can efficiently destroy microorganisms. The test strips measure the minimum effective concentration (MEC) required for high-level disinfection. The test strips are generally specific to the product and they are sold separately. Make sure to have an adequate supply of test strips in stock.

Disadvantages of OPA High-Level Disinfectants

As with all products on the market, there are some disadvantages related to the use of OPA solutions, although they are manageable. According to the FDA report on ortho-phthalaldehyde, the most notable disadvantage is how the product stains proteins. Skin that is exposed to OPA solutions may also stain gray. Patients’ skin or mucous membranes may be stained if equipment sterilized with an OPA solution is not adequately rinsed after soaking.

Disadvantages of Glutaraldehyde High-Level Disinfectants

Products that contain glutaraldehyde or peracetic acid have several drawbacks compared with products that use ortho-phthalaldehyde (OPA). These drawbacks may include shortened life spans of instruments regularly exposed to the disinfectants and possible health risks for staff who work with the products on a regular basis.

Several Examples of High-Level Disinfectants


Since CIDEX OPA was introduced in 1999 it became widely used. Healthcare organizations in every part of the world use CIDEX OPA as a high-level disinfectant for endoscopes, medical instruments, and other medical equipment. CIDEX OPA is the global standard for instrument reprocessing. CIDEX OPA is manufactured by Advanced Sterilization Products, a division of Ethicon (a Johnson & Johnson company).

CIDEX OPA is glutaraldehyde-free and contains 0.55% ortho-phthalaldehyde (OPA). CIDEX OPA has a quick 5-minute soak time at 25°C in an automated endoscope reprocessor and provides high-level disinfection in 12 minutes with manual reprocessing. It easily rinses from medical equipment and medical instruments, especially lumened devices. The near-neutral pH level ensures compatibility with endoscopic instruments and other heat-sensitive semi-critical medical devices.

MetriCide OPA Plus

MetriCide OPA Plus is another OPA high-level disinfectant used for reprocessing heat sensitive semi-critical endoscopes, medical instruments, and other medical equipment. MetriCide OPA Plus is glutaraldehyde-free with ortho-Phthalaldehyde as an active ingredient. MetriCide OPA Plus and can be used manually or in an automated endoscope reprocessor. MetriCide OPA Plus can be reused for up to 30 days in 12 minutes at 20°C when used for manual reprocessing. For automated reprocessing (AER), MetriCide OPA Plus can be reused for up to 14 days in 5 minutes at 25°C. MetriCide OPA Plus Solution Test Strips are required to test and validate the minimum effective concentration level before each use.

Rapicide OPA/28

Rapicide OPA/28 is another high-level disinfectant based on ortho-phthalaldehyde (OPA). Rapicide OPA/28 is a ready-to-use high-level disinfectant that is FDA cleared and CE-mark approved. Rapicide OPA/28 has an active ingredient of 0.575% ortho-phthalaldehyde (OPA). Rapicide OPA/28, like other OPA solutions is bactericidal, fungicidal, and tuberculocidal. Manual high-level disinfection takes 10 minutes at room temperature (20°C minimum) and it can be used for up to 28 days. Test strips are required to validate concentration levels before use. Only Rapicide OPA/28 test strips should be used to verify the minimum effective concentration.

CIDEX Activated Dialdehyde Solution

CIDEX Activated Dialdehyde Solution is a high-level disinfectant with glutaraldehyde as the active ingredient. CIDEX Activated Glutaraldehyde Solution is a broad-spectrum high-level disinfectant that has been used on a wide range of medical instruments (including endoscopes), medical devices, and other medical equipment. CIDEX Activated Glutaraldehyde Solution is a 2.4% glutaraldehyde solution that achieves high-level disinfection in 45 minutes at 25°C.

CIDEX Activated Glutaraldehyde Solution provides a wide spectrum efficacy against bacteria, mycobacteria, viruses and fungi. The solution can also achieve some sporicidal activity with longer exposure time. * (See manufacture’s research for more details.) CIDEX Activated Dialdehyde Solution has a 14-day reuse life. It must be tested and meet the minimum effective concentration level before usage.

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