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Novocain is the trademark name for procaine hydrochloride (C12H20N2O2HCl). It is used as a local anesthetic, particularly in dentistry, surgeries, and spinal anesthesia. A local anesthetic is a drug that temporarily blocks nerve conduction. Novocain is injected into tissue, a nerve trunk, or next to a nerve, or into the spinal canal. Like other local anesthetics, novocain prevents the initiation and conduction of nerve impulses by acting on the neuronal cell membrane. Nerve impulses are conducted by the exchange of sodium and potassium ions through the cell membrane. Novocain alters the permeability of the cell membrane to sodium ions, thus altering the polarity of the membrane and its ability to conduct a nerve impulse. As the anesthetic effect increases, the threshold for electrical stimulation increases and conduction of the nerve impulse decreases. Eventually, the nerve conduction is totally blocked.

Procaine hydrochloride was first synthesized by Einhorn in 1905 as a substitute for cocaine, the first local anesthetic. Cocaine, an alkaloid obtained from the leaves of the coca plant, Erythroxylon coca, is highly addictive and toxic. Procaine hydrochloride replaced cocaine as a local anesthetic because it is much less toxic, cheaper and easier to produce, and it is easier to sterilize. In contrast to cocaine, it is not addictive because it is less stimulating to the central nervous system.

Novocain is absorbed rapidly and begins to act within two to five minutes. The duration of the anesthetic effect usually lasts one to two hours, depending on the method of delivery, concentration of the solution, and the individual patient. Sometimes novocain is mixed with a drug called a vasoconstrictor. A vasoconstrictor constricts the blood vessels, reducing the flow of blood, which slows the rate of absorption so that the anesthetic effect lasts longer. Novocain is an odorless, white crystalline powder that is water soluble. It is available as a prepared solution as either pure or, depending on its intended use, mixed with other drugs.

See also Analgesia.

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