Overview
This lecture covers alkylating agents used for disinfection and sterilization, focusing on formaldehyde, glutaraldehyde, and related compounds, including their uses, properties, and safety concerns.
Alkylating Agents: Mechanism and General Properties
- Alkylating agents replace hydrogen atoms on molecules with alkyl groups, inactivating enzymes and damaging nucleic acids (DNA/RNA).
- They are strong disinfectants/sterilants but are not suitable as antiseptics due to toxicity and carcinogenicity.
- These chemicals can damage living tissue and are generally used only on inanimate surfaces or equipment.
Formaldehyde and Formalin
- Formaldehyde is commonly used as an embalming fluid and laboratory specimen preservative.
- A 37% aqueous solution of formaldehyde is called formalin.
- Formalin can be used as both a liquid disinfectant and a gaseous disinfectant.
- Formaldehyde is highly irritating and carcinogenic; not used on living tissues.
Glutaraldehyde
- Glutaraldehyde is a more effective chemical sterilizing agent than formaldehyde, effective at 2% concentration.
- Commonly sold under the brand name Cydex.
- It is capable of sterilization, removing all living organisms from equipment and surfaces.
Ethylene Oxide
- Ethylene oxide is a gaseous sterilant used for sterilizing packaged materials.
- Historically used in sterilization chambers for bulk sterilization.
- It is the main gaseous sterilant discussed in this context.
Ortho-Phthalaldehyde (OPA)
- OPA is a newer compound replacing glutaraldehyde in modern formulations like Cydex.
- OPA is more effective, especially against Mycobacterium tuberculosis, and is less irritating with a milder odor.
Key Terms & Definitions
- Alkylating agent — a chemical that transfers alkyl groups to molecules, disrupting their function.
- Disinfectant — a substance that eliminates most pathogens on inanimate surfaces.
- Sterilant — an agent that destroys all forms of microbial life.
- Formaldehyde/Formalin — a 37% liquid solution of formaldehyde used for preservation and disinfection.
- Glutaraldehyde — a potent chemical sterilant, effective at 2% concentration.
- Ethylene oxide — a gaseous sterilant for packaged and heat-sensitive materials.
- Ortho-phthalaldehyde (OPA) — a newer, less irritating chemical sterilant replacing glutaraldehyde.
Action Items / Next Steps
- Review the examples and uses of each alkylating agent discussed.
- Be familiar with safety concerns and why these agents are not used as antiseptics.