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Benzocaine
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Benzocaine is a local anesthetic commonly used as a topical pain reliever. It is the active ingredient in many over-the-counter anesthetic ointments (e.g. products for oral ulcers of Anbesol by Wyeth, Kank+a by Blistex, Orabase B and Orajel by Del Pharmaceuticals, and Ultracare by Ultradent). It is also combined with antipyrine to form A/B Otic Drops, (Brand name Auralgan) to relieve earpain and remove cerumen.
ocaine is an ester, and can be prepared from the organic acid PABA (para-aminobenzoic acid) and ethanol by Fischer esterification.
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Encyclopedia
Benzocaine is a local anesthetic commonly used as a topical pain reliever. It is the active ingredient in many over-the-counter anesthetic ointments (e.g. products for oral ulcers of Anbesol by Wyeth, Kank+a by Blistex, Orabase B and Orajel by Del Pharmaceuticals, and Ultracare by Ultradent). It is also combined with antipyrine to form A/B Otic Drops, (Brand name Auralgan) to relieve earpain and remove cerumen.
Chemical properties
Benzocaine is an ester, and can be prepared from the organic acid PABA (para-aminobenzoic acid) and ethanol by Fischer esterification. The melting point of benzocaine is 88-90 degrees Celsius, and the boiling point is 310 degrees Celsius. The density of benzocaine is 1.17 g/cm3.
History
Benzocaine was first synthesised by a German chemical firm named Ritsert, in the town of Eberbach.
How it relieves pain
Pain is caused by the stimulation of free nerve endings. When the nerve endings are stimulated, sodium enters the neuron, which causes an electrical potential to build up in the nerve. Once the electrical potential becomes big enough the signal is propagated down the nerve toward the central nervous system, which interprets this as pain.
Esters of PABA work as a chemical barrier, stopping the sodium from being able to enter 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. 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 aspiration 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.
Other uses
Benzocaine can also be used as a fish tranquilizer. Due to its low solubility in water, a stock solution can be made with ethanol (95%). 25 g of benzocaine per 200 ml ethanol will make a solution strong enough to knock saltwater fish out in 2-4 minutes. They will regain equilibrium after 10-15 minutes. Use 5 ml stock solution per 1 L of saltwater. Some benzocaine will precipitate out of solution when added to the saltwater, so it is recommended to add the volume of stock solution you will be using to a separate container and mix it with some saltwater before adding it to the tank.
Benzocaine is also used as a key ingredient in Phenazone, an anti-inflammatory, and is also used in some glycerol-based ear medications for use in removing excess wax as well as ear conditions such as Otitis Media and swimmers ear.
Benzocaine used to be used as an appetite suppressant in diet products such as Ayds.
It's also the main ingredient in Vagisil.
Benzocaine is often favoured by drug dealers to bulk out their cocaine supplies; while many dealers use the cheaper parcetemol or corn flour, Benzocaine gives a numbing effect (like purer cocaine should have). Although this is a more expensive way of bashing their drugs for resale, the users are often fooled into thinking its high grade, so it can be sold for a higher price.
Benzocaine is also used as the active ingredient in "climax control" Durex Performax condoms to dull nerve endings.
Misconceptions
In Phillip K. Dick's book A Scanner Darkly, 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.
External links
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- - official website
- from the Chemistry Department at Oxford University.
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