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.
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.
Benzocaine was first synthesised by a German chemical firm named Ritsert, in the town of Eberbach.
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.
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.
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%). Preparations of this sort will usually be sufficient to tranquilize saltwater fish for 2–4 minutes, with the fish regaining equilibrium after 10–15 minutes.
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 (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.
Benzocaine is also used as the active ingredient in condoms designed prevent premature ejaculation. Benzocaines acts to desensitize the penis to allow the erection to be maintained.
