Benzocaine

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Benzocaine
Systematic (IUPAC) name
ethyl 4-aminobenzoate
Identifiers
CAS number	94-09-7
ATC code	C05AD03 D04AB04, N01BA05, R02AD01
PubChem	2337
DrugBank	APRD00539
Chemical data
Formula	C9H11NO2
Mol. mass	165.189 g/mol
Pharmacokinetic data
Bioavailability	?
Metabolism	?
Half life	?
Excretion	?
Therapeutic considerations
Pregnancy cat.	C (USA)
Legal status
Routes	topical

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).

[edit] 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.

[edit] History

Benzocaine was first synthesised by a German chemical firm named Ritsert, in the town of Eberbach.

[edit] 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.

[edit] 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.

[edit] Other uses

Benzocaine can also be used as a fish tranquilizer. Due to its low solubility in water, 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.^{[citation needed]}

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.

It is also used in certain condoms to prolong sex by numbing the penis.^[1] It also can be sprayed in the back of the throat to numb the gag reflex during fellatio.

Benzocaine is an ingredient in some anal sex lubricants ^[2] to provide temporary relief to the discomforts of anal sex. It temporarily numbs the sphincter muscle for about 10 to 15 minutes.

Benzocaine used to be used as an appetite suppressant in diet products such as Ayds.

[edit] 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, of course this is not true.

[edit] References

1. ^ 'Delay' condom proves popular - CNN.com
2. ^ AWT: Things you won't find on our website - Product Guides | A Woman's Touch - A comfortable place to celebrate your healthy sexual self. Madison & Milwaukee, WI

[edit] External links

• FDA investigation of the possible adverse effects of benzocaine mouth and throat sprays.
• Orajel.com - official website
• Safety data from the Chemistry Department at Oxford University.