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Benzocaine

Systematic (IUPAC) name
ethyl p-aminobenzoate
Identifiers
CAS number	94-09-7
ATC code	C05AD03 D04AB04, QN01AX92, N01BA05, R02AD01
PubChem	2337
DrugBank	APRD00539
ChemSpider	13854242
Chemical data
Formula	C9H11NO2
Mol. mass	165.189 g/mol
SMILES	eMolecules & PubChem
Pharmacokinetic data
Bioavailability	?
Metabolism	?
Half life	?
Excretion	?
Therapeutic considerations
Pregnancy cat.	C(US)
Legal status
Routes	Topical
Y(what is this?)  (verify)

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.

Contents 1 Chemical properties 2 History 3 How it relieves pain 4 Side effects 5 Other risks 6 Other uses 7 Misconceptions 8 References 9 External links

[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 88-92 degrees Celsius^[1], 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, 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.

Esters of PABA work as a chemical barrier, stopping the sodium entering 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.
• Some condoms designed to prevent premature ejaculation. Benzocaine acts to desensitize the penis, and theoretically allows an erection to be maintained.^[2][3]

[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

1. ^ "Monographs: Pharmaceutical substances: Benzocainum - Benzocaine". The International Pharmacopoeia. http://apps.who.int/phint/en/d/Jb.6.1.62/#docfirsthighlight. Retrieved 29 September 2009. 
2. ^ "Performa". Durex. http://www.durexworld.com/en-GB/Products/Condoms/Pages/Performa.aspx. Retrieved 2009-04-06. 
3. ^ "TROJAN Extended Pleasure Condoms with Climax Control Lubricant". Trojan. http://www.trojancondoms.com/Product/ProductDetails.aspx?ProductId=31. Retrieved 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.

v • d • e Vasoprotectives (C05) Antihemorrhoidals for topical use corticosteroids (Hydrocortisone, Prednisolone, Betamethasone, Fluorometholone, Fluocortolone, Dexamethasone, Fluocinolone acetonide, Fluocinonide) local anesthetics (Lidocaine, Tetracaine, Benzocaine, Cinchocaine, Procaine, Oxetacaine, Pramocaine) other (Tribenoside) Antivaricose therapy heparins or heparinoids for topical use (Organo-heparinoid, Sodium apolate, Heparin, Pentosan polysulfate) sclerosing agents for local injection (Monoethanolamine oleate, Polidocanol, Invert sugar, Sodium tetradecyl sulfate, Phenol) other (Calcium dobesilate) Capillary stabilising agents bioflavonoids (Rutoside, Monoxerutin, Diosmin, Troxerutin, Hidrosmin) - other (Tribenoside)

v • d • e Antipruritics (D04) Antihistamines for topical use Thonzylamine - Mepyramine - Thenalidine - Tripelennamine - Chloropyramine - Promethazine - Tolpropamine - Dimetindene - Clemastine - Bamipine - Isothipendyl - Diphenhydramine - Chlorphenoxamine Anesthetics for topical use Lidocaine - Cinchocaine - Oxybuprocaine - Benzocaine - Quinisocaine - Tetracaine - Pramocaine

v • d • e Anesthetics: Local anesthetics - primarily sodium channel blockers (N01B) Esters Esters of aminobenzoic acid Amylocaine • Benzocaine • Butacaine • Chloroprocaine • Dimethocaine • Meprylcaine • Metabutoxycaine • Orthocaine • Propoxycaine • Procaine • Proxymetacaine • Risocaine • Tetracaine Esters of benzoic acid 3-(p-Fluorobenzoyloxy)tropane • Cocaine • Cyclomethycaine • Piperocaine Other esters Hexylcaine Amides Articaine • Bupivacaine # /Levobupivacaine/Ropivacaine • Carticaine • Cinchocaine • Etidocaine • Lidocaine #  • Mepivacaine • Prilocaine • Trimecaine Combinations Iontocaine • Lidocaine/prilocaine #WHO-EM. ‡Withdrawn from market. CLINICAL TRIALS: †Phase III. §Never to phase III

v • d • e Throat preparations (R02) Antiseptics Ambazone - Dequalinium - Dichlorobenzyl alcohol - Chlorhexidine - Cetylpyridinium - Benzethonium - Myristyl-benzalkonium - Chlorquinaldol - Hexylresorcinol - Acriflavinium chloride - Oxyquinoline - Povidone-iodine - Benzalkonium - Cetrimonium - Hexamidine - Phenol Antibiotics Neomycin - Tyrothricin - Fusafungine - Bacitracin - Gramicidin Local anesthetics Benzocaine - Lidocaine - Cocaine - Dyclonine