Benzocaine: Effects, Uses & Risks

Benzocaine is a drug from the active substance class of local anesthetics. The drug is used primarily in local pain therapy in the area of the skin and mucous membranes.

What is benzocaine?

Benzocaine is a drug from the active substance class of local anesthetics. Possible forms of application include sprays, powders, ointments, suppositories, and solutions. Benzocaine, like lidocaine and procaine, is a local anesthetic. Local anesthetics have a local effect and reversibly reduce the excitability of sensitive nerve fibers. The drug is an ester-type anesthetic. Benzocaine blocks the sodium channels on the nerve cells and thus prevents the transmission of stimuli. The drug is mainly used as a surface anesthetic. In surface anesthesia, the local anesthetic is applied to the mucosa or skin. The site of action is the terminals of the sensitive nerves. Surface anesthetics are primarily used to keep minor procedures pain-free. Possible forms of application include sprays, powders, ointments, suppositories, and solutions.

Pharmacologic action

Benzocaine is a sodium channel blocker. Sodium channels play an important role in stimulus transmission. In the nervous system, stimulus transmission takes the form of electrical impulses. Every cell in the body has a so-called membrane potential. In nerve cells, this is called the resting potential. The resting potential is about -60 mV. It arises because there is an excess of potassium ions inside the cell and an excess of sodium ions outside the cell. Potassium ions are more negatively charged than sodium ions. Therefore, at the resting potential, the inside of the cell is negatively charged compared to the outside. This balance is maintained by the sodium-potassium pump. Only potassium ions enter the cell through it. When a stimulus is applied to the nerve cell, voltage-gated sodium channels in the membrane open and allow an influx of sodium ions. The cell depolarizes, and the membrane potential briefly rises to +30 mV. This state is also known as an action potential. The action potential is carried from nerve cell to nerve cell via the nerve fibers until the target cell is reached and the desired response is initiated. Sodium channel blockers such as benzocaine suppress this process. They prevent the influx of sodium into the cell, so there is no depolarization and thus no action potential. In the case of benzocaine, sensory perception in the area of skin supplied by the corresponding nerve is absent. When a skin site is anesthetized with benzocaine, pain perception is no longer possible.

Medical application and use

The drug is used primarily for local anesthesia of the skin and mucous membranes. The preferred site of application is the mouth and throat. Benzocaine is contained in many medicines for colds. (Over-the-counter) lozenges for sore throats or teething problems also often contain benzocaine. Benzocaine can also be taken to treat stomach pain. Cough suppressant drug preparations also often contain the local anesthetic drug. Creams, solutions and powders are used, for example, to relieve the pain of corns, athlete’s foot, calluses and warts. Suppositories containing benzocaine are also available. These are used for rectal anesthesia for hemorrhoids or other anal discomfort, such as anal eczema or anal itching. Benzocaine can also be used as a delay cream. For this, the drug is applied to the glans penis. The anesthetic effect is intended to reduce sensations in the genital area to prevent premature ejaculation. Before the sexual act begins, the drug should be applied to the glans with the foreskin retracted. The anesthesia begins after just one minute. It subsides after 10 to 15 minutes. Benzocaine is also added to some condoms. The reservoir of these special condoms contains a small amount of benzocaine ointment. The warmth of the penis dissolves the ointment and provides desensitization of the area. However, due to the small dosage and uneven distribution, the desired effect is often not achieved.

Risks and side effects

Benzocaine contains a so-called para-stable primary aromatic amino group.The para groups have a significantly higher allergic potential than non-para-substituted local anesthetics, such as lidocaine. In the event of intolerance, allergic reactions may occur on the skin. Red, brownish or white spots may form on the affected skin areas. Fluid-filled vesicles, purulent pustules or wheals may appear. The skin is reddened and heated. It may hurt or itch. When taken orally, benzocaine may cause stomach pain. A rare side effect is called methemoglobinemia, in which elevated levels of methemoglobin are found in the blood. Above a level of 20 percent, signs of inadequate oxygen supply are seen. These include symptoms such as headache, confusion and a blue coloration of the skin. In severe methemoglobinemia, coma can develop. However, this condition can only be achieved with very high doses of benzocaine.