What is lidocaine?
Lidocaine can be applied directly on the skin surface, inoculated under the skin, injected intravenously or infiltrated into the joint:
- Distributed on the skin, lidocaine is used to relieve itching, burning or pain due to inflammation of the skin.
- In the form of an under-skin injection, lidocaine is used in a variety of areas, ranging from dentistry to minor surgery (aesthetic and non-aesthetic). More generally, lidocaine injections are performed to induce local analgesia in many areas of medicine.
- Intravenously injected, lidocaine is widely used in the treatment of cardiac disorders (eg ventricular arrhythmias) and in the prevention of cardiovascular events such as heart attacks.
- Injected into soft tissues (eg intrasynovial injection), the drug is used in the treatment of joint disorders.
Did you know that ...
According to the classification of the FDA ( Food And Drug Administration ), lidocaine is considered the most suitable local anesthetic drug for pregnant women and breast-feeding women.
Pharmacokinetics and pharmacodynamics
Being an aminoamide, lidocaine differs from other common local analgesics (amino-esters) such as procaine and chlorprocaine. Compared to the latter, lidocaine is considerably more advantageous due to its very rapid and long-lasting action.
On average, the maximum concentration of drug in the blood is reached 20 minutes after administration.
Lidocaine performs its function by inhibiting the voltage-dependent sodium channels of the neurons: by doing so, the drug prevents the nerve fiber from carrying out the painful stimulus, both cutaneously and deeply. 50% of the lidocaine entering the circulation is metabolized within 90-120 minutes of administration; subsequently, the drug is eliminated in the kidney, then excreted in the urine in the form of metabolites (monoethylglycinexylidide and glycinxilidide).
The half-life of lidocaine may be prolonged in the presence of impaired hepatic function or congestive heart failure.
Topical application
As mentioned, lidocaine is an active ingredient with a broad field of application. Applied directly to the skin, the drug is an excellent solution to mitigate - albeit temporarily - the sensation of tingling, burning and pain that accompanies a large part of skin inflammation. Lidocaine is a drug often recommended in the treatment of shingles.
Furthermore, lidocaine is indicated in the treatment of jellyfish stings.
The drug can also be spread on mucous membranes: lidocaine turns out to be a good therapeutic aid to alleviate the fierce burning that accompanies vaginal candidiasis, vaginal itching, anal fissures and hemorrhoids.
It should be emphasized that in these cases lidocaine acts exclusively on the symptom, without however interacting in any way with the triggering cause.
Lidocaine can be administered transdermally before proceeding with invasive diagnostic / therapeutic interventions, such as rachicentesis; in this case the aim is to reduce the perception of pain during the introduction of the lumbar puncture needle.
Under the skin / deep injection
Lidocaine injections are used to numb a given area of the body and thus reduce the pain and discomfort caused by medical procedures such as surgery, catheter insertions or needle introduction.
Injectable lidocaine under the skin is used in different areas. Let's see them in detail:
- In dentistry, lidocaine is used at a concentration of 2%, often in association with adrenaline (a powerful vasoconstrictor). The combination of lidocaine (2%) + adrenaline (1: 80, 000 dilution) is an effective and safe preparation to obtain an excellent analgesic effect before dental operations such as fillings, devitalizations, apicectomy, tooth extraction or whatever.
- In aesthetic medicine, lidocaine is injected under the skin to anesthetize the area to be treated before administering specific medicaments to treat skin blemishes such as wrinkles, crow's feet, scarring etc. (ex. hyaluronic acid filler, polylactic acid, collagen).
- Lidocaine can also be injected epidural: in this case, the drug is used to reduce the discomfort induced by contractions during labor.
Intravenous injection
Given intravenously, lidocaine is widely used for the treatment of ventricular arrhythmias. In particular, the active ingredient is used in the treatment of arrhythmias related to acute myocardial infarction, digitalis intoxication and cardiac catheterization. Despite what has been said, it is good to point out that, today, the routine administration for the prophylaxis of arrhythmias for myocardial infarction does not fully convince the experts; therefore it is not always recommended.
Curiosity
Lidocaine is considered the prototype of the class I antiarrhythmic drugs with greater selectivity: in simple words, the active principle possesses a good local analgesic capacity, but it is devoid of a similar atropine effect (anticholinergic activity). In these cases, lidocaine acts directly on the heart cells.
Intra-articular injection (lidocaine infiltration)
Often, lidocaine is formulated in association with other active ingredients (eg corticosteroids) for intra-articular injection. Lidocaine and corticosteroids, with a clearly different mechanism of action, are combined to encourage the overcoming of morbid / painful conditions on an inflammatory basis. An example is the medicinal specialty Depo-Medrol + Lidocaine: the drug is injected into the soft tissues, intrasynovially (directly into the synovial fluid) and intralesional, for the treatment of synovitis, rheumatoid arthritis and osteoarthritis.
Other uses of lidocaine
The drug can also be used as a temporary remedy against tinnitus, useful for reducing the terrible ringing in the ears.
Lidocaine is often used for the control of epileptic seizures.
Inhaled in the form of a spray / aerosol, lidocaine can be used as an antitussive in the treatment of chronic cough.
Pharmaceutical forms
Lidocaine is available in many pharmaceutical forms. The most common are listed below:
- Patch (for topical application)
- Gel for topical application, often combined with soothing substances such as aloe vera
- Gel / liquid for oral use
- Intravenous injection, possibly combined with adrenaline
- Intravenous infusion
- Injection under the skin as a local anesthetic in combination with adrenaline (useful for reducing or limiting bleeding)
- Self-injectable lidocaine *
- Nasal or spray instillation: in this case, lidocaine is generally associated with phenylephrine
- Preparation by inhalation
- Sterile, aqueous injectable suspension, possibly associated with other active ingredients, such as corticosteroids
Self-injectable lidocaine *
A particular preparation based on lidocaine is sometimes prescribed to some subjects who show evident irregularities in the heart rhythm. The drug, known as LidoPen, is a pre-filled automatic auto-injection device, to be used exclusively in an emergency. The drug is injected in the upper thigh or in the deltoid muscle of the arm, never in the buttocks or near a vein. However, prior to self-inoculation of lidocaine, medical advice is strongly recommended.
Lidocaine: contraindication and side effects »
