Alcohol, primarily in the forms of ethanol and isopropyl alcohol, holds a significant and long-standing place in medical applications. These compounds are employed in controlled settings for various purposes, ranging from external disinfection to internal antidotal treatments. Their chemical properties allow for a diverse range of uses.
Topical Antiseptic and Disinfectant Uses
Alcohol is recognized for its ability to kill microorganisms on surfaces and skin, serving as both an antiseptic and a disinfectant. Before injections, surgeries, or blood draws, alcohol wipes containing concentrations like 70% isopropyl alcohol or 60-90% ethanol are routinely used to prepare the skin. This minimizes the risk of infection by reducing the bacterial load on the skin.
Alcohol is also used for disinfecting medical equipment and environmental surfaces. Stethoscopes and thermometers are often wiped down with alcohol to prevent the spread of pathogens. Alcohol-based hand rubs, commonly known as hand sanitizers, are another prevalent application in healthcare settings, offering a convenient way to maintain hand hygiene.
The germ-killing action of alcohol primarily involves denaturing proteins and dissolving the lipid membranes of microorganisms. Water plays a role in this process, as it is needed for protein coagulation, making solutions of 60-90% alcohol more effective than absolute alcohol.
Alcohol as an Antidote
Ethanol serves as an antidote in cases of poisoning from methanol and ethylene glycol. These substances are toxic because the body metabolizes them into harmful compounds. For instance, methanol is converted into formic acid, which can cause blindness, while ethylene glycol is metabolized into oxalic acid, leading to kidney failure.
Ethanol acts by competitively inhibiting the enzyme alcohol dehydrogenase (ADH). This enzyme breaks down methanol and ethylene glycol into their toxic metabolites. By binding to ADH, ethanol prevents the formation of these byproducts, allowing the unchanged methanol or ethylene glycol to be excreted.
Timely administration of ethanol, often intravenously, is important for its effectiveness. Medical supervision is required to monitor blood alcohol levels and adjust dosing to ensure a therapeutic concentration. While fomepizole is now often the preferred antidote, ethanol remains a treatment option, especially when fomepizole is unavailable.
Alcohol as a Solvent and Preservative
Alcohol is a versatile solvent and preservative in various medical contexts. As a solvent, ethanol is frequently used in pharmaceutical preparations to dissolve active ingredients that are not readily soluble in water. This property is utilized in tinctures, elixirs, and cough syrups, ensuring active components are evenly distributed and precisely dosed. Ethanol dissolves both water-soluble and fat-soluble substances, creating stable and effective liquid medications.
Beyond dissolving active ingredients, alcohol also functions as an antimicrobial preservative in pharmaceutical formulations. Concentrations of 10% or greater inhibit the growth of bacteria, fungi, and other microorganisms, extending shelf life and maintaining efficacy.
Alcohol also preserves biological specimens for laboratory analysis, educational purposes, and long-term storage. Ethanol, often around 70-80% by volume, is commonly employed. It prevents decay by killing bacteria and dehydrating the specimen, removing water and denaturing proteins to fix its shape. This allows for the long-term study and examination of tissues, organs, and even whole organisms.