Benzocaine
Encyclopedia
Benzocaine is a local anesthetic
commonly used as a topical
pain reliever, or in cough drops. It is the active ingredient in many over-the-counter anesthetic ointments (e.g., products for oral ulcers of Anbesol by Pfizer
, Kank-a by Blistex
, and Orabase B and Orajel by Church & Dwight). It is also combined with antipyrine to form A/B Otic Drops
, (Brand name Auralgan) to relieve earpain and remove earwax
.
by Fischer esterification
or via the reduction of ethyl p-nitrobenzoate. Benzocaine is sparingly soluble in water; it is more soluble in dilute acids and very soluble in ethanol, chloroform
and ethyl ether. The melting point of benzocaine is 88-90 degrees Celsius, and the boiling point is about 310 degrees Celsius. The density of benzocaine is 1.17 g/cm3.
and introduced to the market in 1902.
is caused by the stimulation of free nerve ending
s. When the nerve endings are stimulated, sodium enters the neuron
, causing depolarization of the nerve and subsequent initiation of an action potential
. The action potential is propagated down the nerve toward the central nervous system
, which interprets this as pain. Ester
s of PABA work as a chemical barrier, stopping the sodium entering the nerve ending.
Benzocaine also is a well-known cause of methemoglobinemia
. Because it may be used in topical creams with a concentration as much as 20%, it is not difficult to administer a dose sufficient to cause this problem.
by relaxing the gag-reflex and allowing regurgitated stomach contents or oral secretions to enter the airway. Applying an oral anesthetic and consuming beverages before going to bed can be particularly hazardous.
The U.S. Food and Drug Administration
notified healthcare professionals and patients that FDA continues to receive reports of methemoglobinemia
, a serious and potentially fatal adverse effect, associated with benzocaine products.
in the UK. It is being imported in barrels, often 25 kilograms, and sold within the domestic cocaine market where it is used to at least double the weight of imported cocaine. This cocaine is often then repressed into a block and stamped with a logo to suggest it has been freshly imported to the UK from source or transit locations. Benzocaine is visually very similar to cocaine and therefore does not detract from the appearance of quality. One of the other features of this substance is that it remains within the cocaine when it is subjected to Crack manufacture and has subsequently been attributed the slang name of 'magic'. Previous less compatible and inert cutting agents are evaporated within the process and therefore expose extensive adulteration. Benzocaine increases the volume of crack produced and disguises the lower quality or purity as it binds to the cocaine becoming visually indistinguishable within the Crack. The influence of benzocaine has been a significant contributor to the remarkable price increase in high purity cocaine in the UK since 2007 and the very low street quality when sold in heavily adulterated grams.
Benzocaine is used as a key ingredient in numerous pharmaceuticals:
Benzocaine is used in abalone
aquaculture. The strong muscular foot which the abalone use to hold on to the rocks in the wild makes handling the animals difficult. Abalone farmers use benzocaine to mildly anaesthetise them, resulting in the animals loosening their tight grip on the substrate. This enables the farmers to more easily remove them and move them around the farm.
, Jim Barris, one of the main characters attempts to extract pure cocaine out of a bottle of sunburn spray by freezing it, claiming that benzocaine is simply an industry name for cocaine
,.
In reality, cocaine is significantly different from benzocaine.
Local anesthetic
A local anesthetic is a drug that causes reversible local anesthesia, generally for the aim of having local analgesic effect, that is, inducing absence of pain sensation, although other local senses are often affected as well...
commonly used as a topical
Topical
In medicine, a topical medication is applied to body surfaces such as the skin or mucous membranes such as the vagina, anus, throat, eyes and ears.Many topical medications are epicutaneous, meaning that they are applied directly to the skin...
pain reliever, or in cough drops. It is the active ingredient in many over-the-counter anesthetic ointments (e.g., products for oral ulcers of Anbesol by Pfizer
Pfizer
Pfizer, Inc. is an American multinational pharmaceutical corporation. The company is based in New York City, New York with its research headquarters in Groton, Connecticut, United States...
, Kank-a by Blistex
Blistex
Blistex was a small family company in 1947. Its focus was to develop and market lip care products in the United States. It then became a private company based in Oak Brook, Illinois that primarily manufactures lip balm, lip ointment, and other lip-related products...
, and Orabase B and Orajel by Church & Dwight). It is also combined with antipyrine to form A/B Otic Drops
Antipyrine and benzocaine ear drops
Antipyrine and benzocaine ear drops is a medication for the treatment of ear pain caused by otitis media. It combines antipyrine, a pain reliever and benzocaine, a numbing agent to treat ear pain...
, (Brand name Auralgan) to relieve earpain and remove earwax
Earwax
Earwax, also known by the medical term cerumen, is a yellowish waxy substance secreted in the ear canal of humans and other mammals. It protects the skin of the human ear canal, assists in cleaning and lubrication, and also provides some protection from bacteria, fungi, insects and water...
.
Chemical properties
Benzocaine is the ethyl ester of p-aminobenzoic acid (PABA); it can be prepared from PABA and ethanolEthanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
by Fischer esterification
Fischer esterification
Fischer esterification or Fischer–Speier esterification is a special type of esterification by refluxing a carboxylic acid and an alcohol in the presence of an acid catalyst. The reaction was first described by Emil Fischer and Arthur Speier in 1895. Most carboxylic acids are suitable for the...
or via the reduction of ethyl p-nitrobenzoate. Benzocaine is sparingly soluble in water; it is more soluble in dilute acids and very soluble in ethanol, chloroform
Chloroform
Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...
and ethyl ether. The melting point of benzocaine is 88-90 degrees Celsius, and the boiling point is about 310 degrees Celsius. The density of benzocaine is 1.17 g/cm3.
History
Benzocaine was first synthesised in 1890 by a German chemist named Eduard Ritsert, in the town of EberbachEberbach (Baden)
Eberbach is a town in Germany, in northern Baden-Württemberg, located 33 km east of Heidelberg. It belongs to the Rhein-Neckar-Kreis. Its sister city is Ephrata, United States.- Location :...
and introduced to the market in 1902.
Mechanism of action
PainPain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
is caused by the stimulation of free nerve ending
Free nerve ending
A free nerve ending is an unspecialized, afferent nerve ending, meaning it brings information from the body's periphery toward the brain. They function as cutaneous receptors and are essentially used by vertebrates to detect pain.-Structure:...
s. When the nerve endings are stimulated, sodium enters the neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
, causing depolarization of the nerve and subsequent initiation of an action potential
Action potential
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
. The action potential is propagated down the nerve toward the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
, which interprets this as pain. Ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
s of PABA work as a chemical barrier, stopping the sodium entering the nerve ending.
Side effects
Allergic reactions occur with ester local anaesthetics (like benzocaine) because of the PABA structure.Benzocaine also is a well-known cause of methemoglobinemia
Methemoglobinemia
Methemoglobinemia is a disorder characterized by the presence of a higher than normal level of methemoglobin in the blood. Methemoglobin is an oxidized form of hemoglobin that has an increased affinity for oxygen, resulting in a reduced ability to release oxygen to tissues. The oxygen–hemoglobin...
. Because it may be used in topical creams with a concentration as much as 20%, it is not difficult to administer a dose sufficient to cause this problem.
Other risks
Over-application of oral anesthetics such as Anbesol can increase the risk of pulmonary aspirationPulmonary aspiration
Pulmonary aspiration is the entry of material from the oropharynx or gastrointestinal tract into the larynx and lower respiratory tract...
by relaxing the gag-reflex and allowing regurgitated stomach contents or oral secretions to enter the airway. Applying an oral anesthetic and consuming beverages before going to bed can be particularly hazardous.
The U.S. Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
notified healthcare professionals and patients that FDA continues to receive reports of methemoglobinemia
Methemoglobinemia
Methemoglobinemia is a disorder characterized by the presence of a higher than normal level of methemoglobin in the blood. Methemoglobin is an oxidized form of hemoglobin that has an increased affinity for oxygen, resulting in a reduced ability to release oxygen to tissues. The oxygen–hemoglobin...
, a serious and potentially fatal adverse effect, associated with benzocaine products.
Other uses
Benzocaine has become the most commonly encountered sophisticated 'bulking agent' for cocaineCocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...
in the UK. It is being imported in barrels, often 25 kilograms, and sold within the domestic cocaine market where it is used to at least double the weight of imported cocaine. This cocaine is often then repressed into a block and stamped with a logo to suggest it has been freshly imported to the UK from source or transit locations. Benzocaine is visually very similar to cocaine and therefore does not detract from the appearance of quality. One of the other features of this substance is that it remains within the cocaine when it is subjected to Crack manufacture and has subsequently been attributed the slang name of 'magic'. Previous less compatible and inert cutting agents are evaporated within the process and therefore expose extensive adulteration. Benzocaine increases the volume of crack produced and disguises the lower quality or purity as it binds to the cocaine becoming visually indistinguishable within the Crack. The influence of benzocaine has been a significant contributor to the remarkable price increase in high purity cocaine in the UK since 2007 and the very low street quality when sold in heavily adulterated grams.
Benzocaine is used as a key ingredient in numerous pharmaceuticals:
- Over the counter throat lozenges such as CepacolCepacolCepacol , styled Cēpacol, is a brand of personal hygiene products and products for relief of sore throat.They were originally recognized for their yellow mouthwash, the active ingredient of which is Ceepryn , hence the name. The distinctive flavor and color is known as "Original Gold"...
, Life Brand Oral Anaesthetic. - Some glycerol-based ear medications for use in removing excess wax as well as relieving ear conditions such as Otitis MediaOtitis mediaOtitis media is inflammation of the middle ear, or a middle ear infection.It occurs in the area between the tympanic membrane and the inner ear, including a duct known as the eustachian tube. It is one of the two categories of ear inflammation that can underlie what is commonly called an earache,...
and swimmers earOtitis externaOtitis externa is an inflammation of the outer ear and ear canal. Along with otitis media, external otitis is one of the two human conditions commonly called "earache". It also occurs in many other species. Inflammation of the skin of the ear canal is the essence of this disorder...
. - Some previous diet products such as AydsAydsAyds was an appetite-suppressant candy which enjoyed strong sales in the 1970s and early 1980s and was originally manufactured by The Campana Company. It was available in chocolate, chocolate mint, butterscotch or caramel flavors, and later a peanut butter flavor was introduced...
. - Some condoms designed to prevent premature ejaculationPremature ejaculationPremature ejaculation is a condition in which a man ejaculates earlier than he or his partner would like him to. Premature ejaculation is also known as rapid ejaculation, rapid climax, premature climax, or early ejaculation....
. Benzocaine acts to desensitize the penisPenisThe penis is a biological feature of male animals including both vertebrates and invertebrates...
, and theoretically allows an erectionErectionPenile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...
to be maintained.
Benzocaine is used in abalone
Abalone
Abalone , from aulón, are small to very large-sized edible sea snails, marine gastropod molluscs in the family Haliotidae and the genus Haliotis...
aquaculture. The strong muscular foot which the abalone use to hold on to the rocks in the wild makes handling the animals difficult. Abalone farmers use benzocaine to mildly anaesthetise them, resulting in the animals loosening their tight grip on the substrate. This enables the farmers to more easily remove them and move them around the farm.
Misconceptions
In Philip K. Dick's book A Scanner DarklyA Scanner Darkly
A Scanner Darkly is a BSFA Award winning 1977 science fiction novel by American writer Philip K. Dick. The semi-autobiographical story is set in a dystopian Orange County, California, in the then-future of June 1994...
, Jim Barris, one of the main characters attempts to extract pure cocaine out of a bottle of sunburn spray by freezing it, claiming that benzocaine is simply an industry name for cocaine
Cocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...
,.
In reality, cocaine is significantly different from benzocaine.
External links
- http://www.fda.gov/CDER/drug/advisory/benzocaine.htmU.S. Food and Drug AdministrationFood and Drug AdministrationThe Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
investigation of the possible adverse effects of benzocaine mouth and throat sprays.] - Safety data from the Chemistry Department at Oxford University.