Benzocaine
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Benzocaine
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| Systematic (IUPAC) name | |
| ethyl p-aminobenzoate | |
| Identifiers | |
| CAS number | |
| ATC code | C05 D04, QN01, N01, R02 |
| PubChem | |
| DrugBank | |
| ChemSpider | |
| Chemical data | |
| Formula | C9H11NO2 |
| Mol. mass | 165.189 g/mol |
| SMILES | & |
| Pharmacokinetic data | |
| Bioavailability | ? |
| Metabolism | ? |
| Half life | ? |
| Excretion | ? |
| Therapeutic considerations | |
| Pregnancy cat. |
C(US) |
| 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, 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.
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[edit] Chemical properties
Benzocaine is the ethyl ester of p-aminobenzoic acid (PABA); it can be prepared from PABA and ethanol by Fischer esterification or via the reduction of ethyl p-nitrobenzoate. Benzocaine is sparingly soluble in water, though is more soluble in dilute acids and very soluble in ethanol, chloroform and ethyl ether. The melting point of benzocaine is 92-94 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 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.
[edit] Other uses
Benzocaine is used as a key ingredient in numerous pharmecuticals:
- Phenazone, an anti-inflammatory.
- Some glycerol-based ear medications for use in removing excess wax as well as relieving ear conditions such as Otitis Media and swimmers ear.
- Some previous diet products such as Ayds.
- Vagisil.
- Some condoms designed to prevent premature ejaculation. Benzocaine acts to desensitizes the penis to allow the erection to be maintained.[1][2]
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 (implicative of purer cocaine). Although this is a more expensive way of cutting drugs for resale, end users are often fooled into thinking the drug is of higher purity, and are therefore willing to pay more.[citation needed]
[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.
[edit] References
- ^ "Performa". Durex. http://www.durexworld.com/en-GB/Products/Condoms/Pages/Performa.aspx. Retrieved on 2009-04-06.
- ^ "TROJAN Extended Pleasure Condoms with Climax Control Lubricant". Trojan. http://www.trojancondoms.com/Product/ProductDetails.aspx?ProductId=31. Retrieved on 2009-04-06.
[edit] External links
- FDA investigation of the possible adverse effects of benzocaine mouth and throat sprays.
- Safety data from the Chemistry Department at Oxford University.
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