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; it is more soluble in dilute acids and very soluble in ethanol, chloroform and ethyl ether. The melting point of benzocaine is 88-90 °C, and the boiling point is about 310 °C. The density of benzocaine is 1.17 g/cm3.
Benzocaine was first synthesized in 1890 by the German chemist Eduard Ritsert (1859-1946), in the town of Eberbach and introduced to the market in 1902 under the name "Anästhesin".
Mechanism of action
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. Benzocaine acts to inhibit the voltage-dependent sodium channels (VDSCs) on the nerve membrane, stopping the propagation of the action potential.
Over-application of oral anesthetics such as benzocaine 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. The oral use of benzocaine products has been found to be a cause of methemoglobinemia, a disorder in which the amount of oxygen carried by the blood is greatly reduced. This side effect is most common in children under 2 years of age.
Allergic reactions occur with ester local anaesthetics such as benzocaine because of the PABA core structure.
Benzocaine is used as a key ingredient in numerous pharmaceuticals:
Over the counter throat lozenges such as Anbesol and Cepacol.
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 largely inhibits sensitivity on the penis, and can allow for an erection to be maintained longer (in a continuous act) by delaying ejaculation. Conversely, an erection will also fade faster if stimulus is interrupted.
Benzocaine is used in abalone aquaculture. The strong muscular foot which the abalone use to hold on to the rocks in the wild makes handling the animals difficult. Abalone farmers use benzocaine to mildly anaesthetise them, resulting in the animals loosening their tight grip on the substrate. This enables the farmers to more easily remove them and move them around the farm.
Benzocaine is commonly found, particularly in Britain, as an impurity in street cocaine. Whilst giving a numbing effect similar to cocaine on users' gums it does not actually produce the effects of cocaine.
Treating pain from mouth and gum irritations (eg, canker sores). It may also be used for other conditions as determined by your doctor.
Benzocaine gel in a local anesthetic. It works by numbing sensitive and painful areas.
- you are allergic to any ingredient in benzocaine gel or to other local anesthetics (eg, butacaine, procaine)
Contact your doctor or health care provider right away if any of these apply to you.
Some medical conditions may interact with benzocaine gel. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:
- if you are pregnant, planning to become pregnant, or are breast-feeding
- if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
- if you have allergies to medicines, foods, or other substances
Some MEDICINES MAY INTERACT with benzocaine gel. Because little, if any, of benzocaine gel is absorbed into the blood, the risk of it interacting with another medicine is low.
Ask your health care provider if benzocaine gel may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.
Use benzocaine gel as directed by your doctor. Check the label on the medicine for exact dosing instructions.
- An adult should supervise the use of benzocaine gel if the patient is a CHILD younger than 12 years old.
- To use a dose of benzocaine gel, follow the instructions provided by your doctor or on the product label.
- Wash your hands before and after you use benzocaine gel. Apply medicine to the affected area by using cotton, a cotton swab, or a clean fingertip.
- Do not eat or drink for at least 1 hour after using benzocaine gel.
- Do not use benzocaine gel within 1 hour of your previous dose or use more than 4 times per day, unless your doctor or dentist tells you otherwise.
- If you miss a dose of benzocaine gel, use it as soon as you remember. Continue to use it as directed by your doctor or on the package label.
Ask your health care provider any questions you may have about how to use benzocaine gel.
Do not get benzocaine gel in your eyes. If you get it in your eyes, rinse right away with cool water.
Do NOT use more than the recommended dose or use for longer than 7 days without checking with your doctor or dentist.
If your symptoms do not get better within 7 days or if they get worse, check with your doctor.
Contact your doctor if you have persistent or worsening pain, redness, or irritation, or if you develop swelling, rash, or a fever. Tell your doctor if you have mouth sores that keep coming back.
Benzocaine gel may cause harm if more than the amount used to treat pain is swallowed. If this occurs, contact your poison control center or emergency room right away.
Benzocaine gel should not be used in CHILDREN younger than 2 years old without checking with the child's doctor or dentist; safety and effectiveness in these children have not been confirmed.
PREGNANCY and BREAST-FEEDING: It is not known if benzocaine gel can cause harm to the fetus. If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using benzocaine gel while you are pregnant. It is not known if benzocaine gel is found in breast milk. If you are or will be breast-feeding while you use benzocaine gel, check with your doctor. Discuss any possible risks to your baby.
All medicines may cause side effects, but many people have no, or minor, side effects. No COMMON side effects have been reported with benzocaine gel. Seek medical attention right away if any of these SEVERE side effects occur:
Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); mouth burning, irritation, redness, swelling, or tenderness.
This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.
- If you have any questions about benzocaine gel, please talk with your doctor, pharmacist, or other health care provider.
- Benzocaine gel is to be used only by the patient for whom it is prescribed. Do not share it with other people.
- If your symptoms do not improve or if they become worse, check with your doctor.
- Check with your pharmacist about how to dispose of unused medicine.
This information should not be used to decide whether or not to take benzocaine gel or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about benzocaine gel. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to benzocaine gel. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using benzocaine gel.
- Benzocaine News and information
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