Cocaine (benzoylmethylecgonine)

          Cocaine (benzoylmethylecgonine) (INN) is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" and the alkaloid suffix -ine, forming cocaine. It is a stimulant, an appetite suppressant, and a topical anesthetic. Biologically, cocaine acts as a serotonin–norepinephrine–dopamine reuptake inhibitor, also known as a triple reuptake inhibitor (TRI). It is addictive because of its effect on the mesolimbic reward pathway^.

Unlike most molecules, cocaine has pockets with both high hydrophilic and lipophilic efficiency, violating the rule of hydrophilic-lipophilic balance. This causes it to cross the blood–brain barrier far better than other psychoactive chemicals. It is illegal to possess, grow, or distribute cocaine for non-medicinal and non-government-sanctioned purposes in almost every country. Still it is consumed extensively throughout the world.

         
          Cocaine is a powerful nervous system stimulant Its effects can last from 15–30 minutes to an hour, depending on the route of administration. Cocaine increases alertness, feelings of well-being and euphoria, energy and motor activity, feelings of competence and sexuality. Athletic performance may be enhanced in sports where sustained attention and endurance is required. Anxiety, paranoia and restlessness are also frequent. With excessive dosage, tremors, convulsions and increased body temperature are observed. Occasional cocaine use does not typically lead to severe or even minor physical or social problems

          With excessive or prolonged use, the drug can cause itching, tachycardia, hallucinations, and paranoid delusions. Overdoses cause hyperthermia and a marked elevation of blood pressure, which can be life-threatening.

Chronic

Side effects of chronic cocaine use
 
Cocaine hydrochloride
           Chronic cocaine intake causes brain cells to adapt functionally to strong imbalances of transmitter levels in order to compensate extremes. Thus, receptors disappear from the cell surface or reappear on it, resulting more or less in an "off" or "working mode" respectively, or they change their susceptibility for binding partners (ligands) – mechanisms called down-/upregulation. However, studies suggest cocaine abusers do not show normal age-related loss of striatal dopamine transporter (DAT) sites, suggesting cocaine has neuroprotective properties for dopamine neurons. The experience of insatiable hunger, aches, insomnia/oversleeping, lethargy, and persistent runny nose are often described as very unpleasant. Depression with suicidal ideation may develop in very heavy users. Finally, a loss of vesicular monoamine transporters, neurofilament proteins, and other morphological changes appear to indicate a long term damage of dopamine neurons. All these effects contribute a rise in tolerance thus requiring a larger dosage to achieve the same effect.

         The lack of normal amounts of serotonin and dopamine in the brain is the cause of the dysphoria and depression felt after the initial high. Physical withdrawal is not dangerous, and is in fact restorative. Physiological changes caused by cocaine withdrawal include vivid and unpleasant dreams, insomnia or hypersomnia, increased appetite and psychomotor retardation or agitation.

          Physical side effects from chronic smoking of cocaine include hemoptysis, bronchospasm, pruritus, fever, diffuse alveolar infiltrates without effusions, pulmonary and systemic eosinophilia, chest pain, lung trauma, sore throat, asthma, hoarse voice, dyspnea (shortness of breath), and an aching, flu-like syndrome. Cocaine constricts blood vessels, dilates pupils, and increases body temperature, heart rate, and blood pressure. It can also cause headaches and gastrointestinal complications such as abdominal pain and nausea. A common but untrue belief is that the smoking of cocaine chemically breaks down tooth enamel and causes tooth decay. However, cocaine does often cause involuntary tooth grinding, known as bruxism, which can deteriorate tooth enamel and lead to gingivitis. Additionally, stimulants like cocaine, methamphetamine, and even caffeine cause dehydration and dry mouth. Since saliva is an important mechanism in maintaining one's oral pH level, chronic stimulant abusers who do not hydrate sufficiently may experience demineralization of their teeth due to the pH of the tooth surface dropping too low .

          Chronic intranasal usage can degrade the cartilage separating the nostrils (the septum nasi), leading eventually to its complete disappearance. Due to the absorption of the cocaine from cocaine hydrochloride, the remaining hydrochloride forms a dilute hydrochloric acid.

          Cocaine may also greatly increase this risk of developing rare autoimmune or connective tissue diseases such as lupus, Goodpasture's disease, vasculitis, glomerulonephritis, Stevens–Johnson syndrome and other diseases. It can also cause a wide array of kidney diseases and renal failure.

          Cocaine misuse doubles both the risks of hemorrhagic and ischemic strokes, as well as increases the risk of other infarctions, such as myocardial infarction.
Addiction
 Cocaine dependence

          Cocaine dependence (or addiction) is psychological dependency on the regular use of cocaine. Cocaine dependency may result in physiological damage, lethargy, psychosis, depression, akathisia, and fatal overdose.

Biosynthesis

Biosynthesis of cocaine

          The biosynthesis begins with L-Glutamine, which is derived to L-ornithine in plants. The major contribution of L-ornithine and L-arginine as a precursor to the tropane ring was confirmed by Edward Leete. Ornithine then undergoes a Pyridoxal phosphate-dependent decarboxylation to form putrescine. In animals, however, the urea cycle derives putrescine from ornithine. L-ornithine is converted to L-arginine, which is then decarboxylated via PLP to form agmatine. Hydrolysis of the imine derives N-carbamoylputrescine followed with hydrolysis of the urea to form putrescine. The separate pathways of converting ornithine to putrescine in plants and animals have converged. A SAM-dependent N-methylation of putrescine gives the N-methylputrescine product, which then undergoes oxidative deamination by the action of diamine oxidase to yield the aminoaldehyde. Schiff base formation confirms the biosynthesis of the N-methyl-Δ1-pyrrolinium cation.

Biosynthesis of cocaine

          The additional carbon atoms required for the synthesis of cocaine are derived from acetyl-CoA, by addition of two acetyl-CoA units to the N-methyl-Δ1-pyrrolinium cation. The first addition is a Mannich-like reaction with the enolate anion from acetyl-CoA acting as a nucleophile towards the pyrrolinium cation. The second addition occurs through a Claisen condensation. This produces a racemic mixture of the 2-substituted pyrrolidine, with the retention of the thioester from the Claisen condensation. In formation of tropinone from racemic ethyl [2,3-13C2]4(Nmethyl-2-pyrrolidinyl)-3-oxobutanoate there is no preference for either stereoisomer. In the biosynthesis of cocaine, however, only the (S)-enantiomer can cyclize to form the tropane ring system of cocaine. The stereoselectivity of this reaction was further investigated through study of prochiral methylene hydrogen discrimination. This is due to the extra chiral center at C-2. This process occurs through an oxidation, which regenerates the pyrrolinium cation and formation of an enolate anion, and an intramolecular Mannich reaction. The tropane ring system undergoes hydrolysis, SAM-dependent methylation, and reduction via NADPH for the formation of methylecgonine. The benzoyl moiety required for the formation of the cocaine diester is synthesized from phenylalanine via cinnamic acid.[33] Benzoyl-CoA then combines the two units to form cocaine.
Robert Robinson's acetonedicarboxylate

         The biosynthesis of the tropane alkaloid, however, is still uncertain. Hemscheidt proposes that Robinson's acetonedicarboxylate emerges as a potential intermediate for this reaction. Condensation of N-methylpyrrolinium and acetonedicarboxylate would generate the oxobutyrate. Decarboxylation leads to tropane alkaloid formation.
Reduction of tropinone

          The reduction of tropinone is mediated by NADPH-dependent reductase enzymes, which have been characterized in multiple plant species. These plant species all contain two types of the reductase enzymes, tropinone reductase I and tropinone reductase II. TRI produces tropine and TRII produces pseudotropine. Due to differing kinetic and pH/activity characteristics of the enzymes and by the 25-fold higher activity of TRI over TRII, the majority of the tropinone reduction is from TRI to form tropine.
Pharmacology

A pile of cocaine hydrochloride

A piece of compressed cocaine powder

          Cocaine in its purest form is a white, pearly product. Cocaine appearing in powder form is a salt, typically cocaine hydrochloride (CAS 53-21-4). Street market cocaine is frequently adulterated or “cut” with various powdery fillers to increase its weight; the substances most commonly used in this process are baking soda; sugars, such as lactose, dextrose, inositol, and mannitol; and local anesthetics, such as lidocaine or benzocaine, which mimic or add to cocaine's numbing effect on mucous membranes. Cocaine may also be "cut" with other stimulants such as methamphetamine. Adulterated cocaine is often a white, off-white or pinkish powder.

The color of “crack” cocaine depends upon several factors including the origin of the cocaine used, the method of preparation – with ammonia or baking soda – and the presence of impurities, but will generally range from white to a yellowish cream to a light brown. Its texture will also depend on the adulterants, origin and processing of the powdered cocaine, and the method of converting the base. It ranges from a crumbly texture, sometimes extremely oily, to a hard, almost crystalline nature.

Forms of cocaine

Salts

          Cocaine is a weakly alkaline compound (an "alkaloid"), and can therefore combine with acidic compounds to form various salts. The hydrochloride (HCl) salt of cocaine is by far the most commonly encountered, although the sulfate (-SO4) and the nitrate (-NO3) are occasionally seen. Different salts dissolve to a greater or lesser extent in various solvents – the hydrochloride salt is polar in character and is quite soluble in water.

          As the name implies, “freebase” is the base form of cocaine, as opposed to the salt form. It is practically insoluble in water whereas hydrochloride salt is water soluble.

          Smoking freebase cocaine has the additional effect of releasing methylecgonidine into the user's system due to the pyrolysis of the substance (a side effect which insufflating or injecting powder cocaine does not create). Some research suggests that smoking freebase cocaine can be even more cardiotoxic than other routes of administration because of methylecgonidine's effects on lung tissue and liver tissue.

          Pure cocaine is prepared by neutralizing its compounding salt with an alkaline solution which will precipitate to non-polar basic cocaine. It is further refined through aqueous-solvent Liquid-liquid extraction.

Crack cocaine

          Crack is a lower purity form of free-base cocaine that is usually produced by neutralization of cocaine hydrochloride with a solution of baking soda (sodium bicarbonate, NaHCO3) and water, producing a very hard/brittle, off-white-to-brown colored, amorphous material that contains sodium carbonate, entrapped water, and other by-products as the main impurities.

          The "freebase" and "crack" forms of cocaine are usually administered by vaporization of the powdered substance into smoke, which is then inhaled. The origin of the name "crack" comes from the "crackling" sound (and hence the onomatopoeic moniker “crack”) that is produced when the cocaine and its impurities (i.e. water, sodium bicarbonate) are heated past the point of vaporization. Pure cocaine base/crack is easy to smoke because it vaporizes smoothly, with little or no decomposition at around 98°C,[citation needed][dubious – discuss] which is below the boiling point of water. The smoke produced from cocaine base is usually described as having a very distinctive, pleasant taste.

          In contrast, cocaine hydrochloride does not vaporize until heated to a much higher temperature (about 197°C), and considerable decomposition/burning occurs at these high temperatures. This effectively destroys some of the cocaine, and yields a sharp, acrid, and foul-tasting smoke.

          Smoking or vaporizing cocaine and inhaling it into the lungs produces an almost immediate "high" that can be very powerful (and addicting) quite rapidly – this initial crescendo of stimulation is known as a "rush". While the stimulating effects may last for hours, the euphoric sensation is very brief, prompting the user to smoke more immediately.
Coca leaf infusions

          Coca herbal infusion (also referred to as Coca tea) is used in coca-leaf producing countries much as any herbal medicinal infusion would elsewhere in the world. The free and legal commercialization of dried coca leaves under the form of filtration bags to be used as "coca tea" has been actively promoted by the governments of Peru and Bolivia for many years as a drink having medicinal powers. Visitors to the city of Cuzco in Peru, and La Paz in Bolivia are greeted with the offering of coca leaf infusions (prepared in tea pots with whole coca leaves) purportedly to help the newly arrived traveler overcome the malaise of high altitude sickness. The effects of drinking coca tea are a mild stimulation and mood lift. It does not produce any significant numbing of the mouth nor does it give a rush like snorting cocaine. In order to prevent the demonization of this product, its promoters publicize the unproven concept that much of the effect of the ingestion of coca leaf infusion would come from the secondary alkaloids, as being not only quantitatively different from pure cocaine but also qualitatively different.

         It has been promoted as an adjuvant for the treatment of cocaine dependence. In one controversial study, coca leaf infusion was used -in addition to counseling- to treat 23 addicted coca-paste smokers in Lima, Peru. Relapses fell from an average of four times per month before treatment with coca tea to one during the treatment. The duration of abstinence increased from an average of 32 days prior to treatment to 217 days during treatment. These results suggest that the administration of coca leaf infusion plus counseling would be an effective method for preventing relapse during treatment for cocaine addiction. Importantly, these results also suggest strongly that the primary pharmacologically active metabolite in coca leaf infusions is actually cocaine and not the secondary alkaloids.

The cocaine metabolite benzoylecgonine can be detected in the urine of people a few hours after drinking one cup of coca leaf infusion