Lidocaine

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Lidocaine is one of the most important therapeutic agents for cardiac arrhythmias. In addition, it is also used as a local anesthetic and for the prevention and treatment of pain. For example, a lidocaine cream can be applied to the affected area of skin before minor surgical procedures. The application for local neuropathic pain in the form of a plaster is new. Here you can read everything you need to know about lidocaine.

This is how lidocaine works

Lidocaine is an active ingredient from the Ib antiarrhythmic class, so it suppresses the influx of sodium ions through its channels in the heart. When used locally, lidocaine also blocks sodium channels and in this way inhibits the sensation and transmission of pain (local anesthetic effect).

Antiarrhythmic effect

In order to trigger a single heartbeat, many individual steps are required in the heart muscles and the associated nerve tracts. Mainly so-called sodium channels in the cell membranes are involved, which become permeable to small, charged sodium particles (sodium ions) when excited. In this way, excitation is transmitted along the nerve pathways. At the end of this transmission is the tensing of the heart muscles (contraction).

In patients who suffer from irregular heartbeat (arrhythmias), the heart beats irregularly. If such irregularities occur frequently, adequate blood flow to the body is no longer guaranteed.

It may then be necessary to treat the arrhythmias with medication. So-called antiarrhythmics such as lidocaine are used. It blocks the sodium channels, which can normalize the heartbeat.

Local anesthetic effect

Sodium channels are also required for the transmission of pain stimuli. They allow the stimulus to be transmitted along the nerve pathways to the spinal cord and brain, so that one can react to the stimulus (for example, by quickly pulling the hand away from a hot stove).

A targeted blockade of the sodium channels by lidocaine, for example in the context of conduction or infiltration anesthesia, inhibits the transmission of painful stimuli - the treated area is briefly numb.

Uptake, breakdown and excretion

Lidocaine is hardly absorbed into the blood through the intestines at all. Therefore, it cannot be taken by mouth to treat irregular heartbeat. Instead, it is injected into a vein (intravenous administration). The antiarrhythmic effect occurs within a few minutes and lasts for about 20 minutes.

When used as an anesthetic, lidocaine is applied externally to the relevant skin area (e.g. as an ointment) or injected near a supplying nerve. Depending on the chosen administration, the effect occurs after about 20 minutes (ointment) or immediately (injection).

The active ingredient is broken down in the liver using certain enzymes. The breakdown products are excreted through the kidneys.

When is lidocaine used?

The areas of application (indications) of lidocaine include:

certain types of irregular heartbeat
Anesthesia of the mucous membrane in the case of pain and slight inflammation (e.g. inflammation in the mouth and throat, hemorrhoids)
Infiltration, conduction and epidural anesthesia to block nerves
Neural therapy (only certain lidocaine preparations are approved for this)
premature ejaculation (lidocaine ointment or lidocaine spray)
local neuropathic pain after a herpes zoster infection, i.e. with shingles (plaster containing lidocaine)

This is how lidocaine is used

The active ingredient must be used differently depending on the therapeutic goal.

For example, a lidocaine ointment is used to numb the skin.

Relief of pain in the area of the mucous membranes can be achieved using lidocaine gel, lidocaine suppositories or lidocaine spray. The dosage depends on the area to be anesthetized. Children and elderly patients receive a lower dose.

In the case of cardiac arrhythmias, the active ingredient must be injected directly into the blood in the form of a solution.

For neuropathic pain, a lidocaine patch is placed on the affected area for a maximum of 12 hours.

What are the side effects of lidocaine?

Local use on skin and mucous membranes

Frequently (i.e. one to ten percent of those treated) the topical application of lidocaine causes side effects such as temporary skin irritation or reddening. Allergic reactions occur rarely (less than 0.1 percent of those treated).

Intravenous use

Often, the intravenous use of lidocaine leads to drowsiness, dizziness, confusion, hallucinations and gastrointestinal complaints. Allergic reactions, muscle twitching, difficulty breathing and a slow heartbeat (bradycardia) occur rarely.

What should be considered when using lidocaine?

Contraindications

Medicines containing lidocaine must not be injected if:

severe cardiac dysfunction (blockage of the transmission of stimuli, poor performance of the heart)
Heart attack in the past three months
Volume depletion or shock
severe hypotension (low blood pressure <90 / 50mmgHg)
certain neurological diseases (e.g. multiple sclerosis)

limitations

Lidocaine should only be used with caution in the case of mild cardiac dysfunction, too slow heartbeat (bradycardia), liver and kidney dysfunction, low blood pressure and low blood salt values (potassium).

If the active substance is used for a longer period of time, the blood values must be checked regularly.

Patches containing active ingredients may only be applied to uninjured areas of skin without skin irritation.

Interactions

Interactions with other drugs mainly occur when administered intravenously.

Various anti-epilepsy agents (carbamazepine, phenobarbital, phenytoin, primidone) reduce the effect of lidocaine.

The following drugs, on the other hand, can increase the effects and side effects of lidocaine:

Cimetidine (medicine for heartburn and stomach ulcers)
Norepinephrine (for cardiac dysfunction)

Age restriction

Approval is product-specific. In principle, injection solutions, gels, ointments and suppositories containing lidocaine are intended for use from the first year of life. Lozenges and sprays containing lidocaine are permitted from the age of six.

Combination preparations (e.g. suppositories with other active ingredients) and plasters containing lidocaine must not be used in children and adolescents under 18 years of age.

pregnancy and breast feeding period

Medication containing lidocaine should only be used during pregnancy and breastfeeding if absolutely necessary.

It can be used as a local anesthetic during pregnancy. As an antiarrhythmic, lidocaine is only given to pregnant women if they have severe cardiac arrhythmias.

Lidocaine can pass into breast milk - but it can only be found in small quantities in milk when administered intravenously or as part of anesthesia to block nerves. To date, there have also been no reports of side effects in breastfed infants. Lidocaine can therefore be used during breastfeeding if indicated.

Driving and using machines

The use of lidocaine can impair the ability to react. The attending physician therefore decides on a case-by-case basis whether a patient can still actively participate in road traffic or operate heavy machinery.

How to get medication with lidocaine

Medicines that are intended for use on the skin and mucous membranes are sometimes available over the counter in pharmacies in Germany, Austria and Switzerland. Lidocaine solutions for intravenous use are only available from pharmacies with a doctor's prescription.

Since when has lidocaine been known?

The active ingredient has been known for a long time. It was first discovered that it had an anesthetic effect. Shortly afterwards, the antiarrhythmic effects of lidocaine were also found.

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