Anesthetics are critical to modern medicine. Local or topical compounds assist doctors in numbing body parts for minor surgical procedures, while general anesthetics are used for major invasive surgery. Whatever the category of anesthetic, the creation and manufacture of modern anesthetics is dependent on the use of inert oils as carriers for the active ingredients.

Inert oils, as the name suggests, are substances that have few active properties. When brought into contact with human tissue, they typically have limited reactive properties and serve mostly as carriers for anything bonded chemically to them. Natural inert oils include mineral oils and various vegetable oils such as almond oil, walnut oil, or tung oil. More commonly used in medical applications are various synthetic hydrocarbon based oils made by a number for different manufacturers. In addition to their medical applications, both natural and synthetic inert oils have many uses as lubricants, polishes, and creases.

The medical need for these inert oils becomes clearer when one understands that the basic building blocks of modern anesthetics are halocarbon compounds. Halocarbons are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms: fluorine, chlorine, bromine or iodine. For anesthetic use, the most commonly used halocarbons are those which use some form of fluorine, frequently in combination with chlorine.

By themselves, both fluorine and chlorine are dangerous chemicals which can be extremely toxic. When combined with one of the various types of inert oils, however, these atoms bind tightly to the atoms of the hydrocarbon-based oil and create a halocarbon, thus becoming more stable, with more predictable and controllable properties. Both injectable and inhalation anesthetics make use of hydrocarbon based inert oils to create halocarbons; inhalation anesthetics are vaporized and delivered to the patient through the use of complex machines that vaporize the compound.

Various forms of fluorine-based anesthetics have been in regular medical use for many years. Although the mechanism by which general anesthesia works is still not clearly understood, advances in anesthetic formulation have made contemporary surgery far more effective by allowing surgeons to operate for longer periods of time, thus creating the opportunity for doctors to perform the delicate and complex procedures that have extended the quality and quantity of life for many patients.

An added benefit of these compounds is that they help reduce the risk of dangerous chemical reactions with the oxygen used during surgery. Fluorine combines easily with oxygen and can created hazardous and toxic gases that pose dangers not only to the patient but also to the surgical team. Since the inert oils affix themselves to the fluorine and chlorine atoms, they serve to reduce this risk.

Researchers continue to work with ever-changing combinations of inert oils and anesthetic agents to create medicines that can be targeted for different results. Some produce deep, unconscious states that can be regulated to last for hours, while others are designed to allow for quick recovery after surgery. Multiple types of anesthesia are also necessary to allow for the possibility of allergic reactions.

While there has been considerable research in recent years on the use of other types of anesthetics that do not rely on these compounds (the most notable example of which involves various inert gases such as xenon), problems with handling waste, avoiding surgical theater pollution, and developing effective regulatory equipment have meant that the use of halocarbon based general anesthesia remains dominant.

Local and topical anesthetics also make use of inert oils in their formulas. In these substances, the oils are used as carriers to bring the volatile active ingredients safely into the patient's system. Such anesthetics work by bonding to local nerve receptors and interfering with the body's usual pain responses. As with general anesthesia, researchers continue to experiment with new forms of halocarbons and inert oils to increase the effectiveness and expand the range of uses for these drugs.

At the lowest end of the anesthetic spectrum are various topical mixtures that are used in a wide variety of over-the counter products. Creams and lotions used for various skin conditions and muscle pains use synthetic and natural inert oils to carry mild anesthetics such as menthol into affected tissue. In addition to the above mentioned almond and walnut oils, a common inert vegetable oil used in these products is tea tree oil.

Science continues to develop new methods for the delivery of anesthesia. While developments on the horizon promise an eventual change in approach, the effectiveness and specificity with which the combination of inert oils and various fluoride compounds can be applied suggest that these medicines will be around for some time to come.