cocaine -- 3/2/22
Today's selection -- from Anaesthesia: A Very Short Introduction by Aidan O'Donnell. Cocaine:
"Cocaine is an alkaloid found in the leaves of the coca plant, Erythroxylum coca, which is native to South America. For centuries, the leaves have been chewed by South American people as a mild stimulant and appetite suppressant. Coca was brought back to Europe by the Spanish in the 16th century. Cocaine itself was first isolated by Friedrich Gaedcke in 1855, and an improved purification process was developed by Albert Niemann in 1860. Later, it came to be incorporated into tonic drinks, such as Coca-Cola in 1866, and was available over the counter at Harrods in London until as late as 1916.
|Coquero (Figure Chewing Coca), 850–1500 C.E.|
"In 1884, a Viennese ophthalmologist called Karl Koller, an associate of Sigmund Freud, noted that drops of cocaine solution introduced into the eye produced local anaesthesia sufficient for the patient to tolerate eye surgery. The following year, William Halsted and Richard Hall in New York experimented with injecting cocaine around peripheral nerves, to cause numbness. As a result of their experiments on themselves, Halsted and Hall became addicted to cocaine.
"Cocaine has two pharmacological actions. First, it blocks voltage-gated sodium channels in neurons, making it an effective local anaesthetic agent. However, it also acts in the central system, blocking the reuptake of stimulatory neurotransmitters (such as dopamine, serotonin, and noradrenaline) at synapses, thereby enhancing their actions. It is this second action which is responsible for cocaine's stimulant properties, but the accompanying euphoria is responsible for the addictive nature of cocaine. Arthur Conan Doyle described Sherlock Holmes injecting himself with cocaine, to Dr. Watson's great disapproval.
"For two decades, scientists searched for a drug with the local anaesthetic properties of cocaine, but without its addictive properties. Success came in 1904, to French pharmacologist Ernest Fourneau, who synthesized amylocaine at the Pasteur Institute. Fourneau gave it the trade name Stovaine, after the English translation of his surname. Since then, almost all local anaesthetic drugs have carried the suffix -caine. Amylocaine has the same action on nerve fibers as cocaine, but lacks the CNS properties of cocaine. At about the same time, Alfred Einhorn in Germany synthesized procaine, whose trade name is Novocaine. (Simpson had managed to create local anaesthesia in the centipede using chloroform, but failed in his attempts to scale up his experiment to humans, using himself as the subject.)
"Amylocaine and its successors are structurally different from cocaine, but all share some common features. Each agent has a ring-shaped 'head', joined by a short linkage to a water-soluble 'tail'. The early agents such as amylocaine and procaine had an ester linkage. This can be broken down in the bloodstream, giving these agents a very short duration of action. In addition, the breakdown products were shown to be associated with a high incidence of allergic reaction. Later agents substituted an amide linkage, which made the molecule much more stable, with improved protein binding and hence a longer duration of action.
"The first amide local anaesthetic was lidocaine (lignocaine), synthesized in 1943 by Swedish chemist Nils Löfgren. More recent local anaesthetic drugs include bupivacaine (1963) and ropivacaine (1993)."