Lidocaine: uses and side effects

Lidocaine is an anesthetic drug that belongs to the pharmacological family of aminoamides. This anesthetic drug is widely used in the area of ​​dentistry.

Specifically, it is a local anesthetic type amide and It can be used in the form of ointment, gel, patch or spray for topical use, as well as oral solution and injection for local anesthesia.

It has been used as a local anesthetic since 1948, but it was not until 1962 when it was first used with the indication to combat ventricular tachycardia or ventricular fibrillation.

How does lidocaine exert its effect on the body?

Lidocaine, as we know, is a drug that triggers both anesthetic and antiarrhythmic effects. For this reason, it has a double mechanism of action. Let's see each one separately.

Anesthetic effect

These types of drugs owe their effectiveness to their ability to inhibit or the generation or transmission of nerve impulses in a reversible way.

In order to achieve this effect, lidocaine decreases the permeability of the nerve membrane to sodium. This action causes the membrane depolarization rate to decrease and, as a consequence, the threshold for electrical excitability increases.

In short, in order to trigger its anesthetic action, lidocaine blocks the onset and spread of action potentials, preventing the increase in sodium conductance, by blocking the voltage dependent sodium channels.

At the electrophysiological level, depolarization speed decreases and therefore driving speed, extending the refractory period. At low doses, it reduces the elevation of the action potential and decreases the trigger frequency. When the doses are higher, it prevents the triggering of the action potential, since it physically clogs the pore that is in the membrane.

Read also: Dental anesthesia and analgesia in dentistry

Antiarrhythmic effect

As for antiarrhythmic drugs, are those used to suppress or prevent heart rhythm disturbances. In this sense, lidocaine is able to inhibit the entry of sodium through the rapid channels of the heart's cell membrane. In this way, the recovery period after repolarization is increased.

Lidocaine suppresses automatism, which is the heart's ability to beat automatically, and decreases the refractory period and the duration of the action potential in the His-Purkinje system at low concentrations. In addition, it is able to suppress spontaneous depolarizations in the ventricles, hence its effectiveness in the aforementioned indications.

Pharmacokinetics: what happens to lidocaine in the body?

Pharmacokinetics includes the processes of absorption, distribution, metabolism and elimination of a drug. In this sense, lidocaine, as we have seen, It can be administered by different routes. Depending on the route by which it is administered, the pharmacokinetic values ​​vary.

As for oral administration, although it is hardly used, it has almost complete absorption. However, It has a very low bioavailability of 35%. Bioavailability is the percentage of drug that is available at the time of performing the action in the body after a dose.

On the other hand, when used topically, lidocaine has a duration of action of between 30-60 minutes with peak effects occurring within the first 2.5 minutes. Local anesthesia begins to occur within 3 minutes of application. Once the patch is removed, local anesthesia can be extended up to approximately 40 minutes.

By last, after an intravenous injection, lidocaine is distributed in two phases. The first represents the distribution of lidocaine in the most perfused tissues. The second phase is slower and the drug is distributed in adipose tissues and skeletal muscle. The onset of intravenous dose action is immediate. However, when administered intramuscularly, the action begins after 5-15 minutes.

You may be interested: Tips for giving an intramuscular injection

Adverse reactions

Lidocaine, like all medications on the market, It is not exempt from producing a series of adverse effects What must be considered. Among the most common, we can mention those related to the central nervous system. Among them are:

In addition, as it also has effects on the heart, when lidocaine doses are very high, some of the following unwanted effects may also appear:

conclusion

Lidocaine is a drug subject to medical prescription. It has antiarrhythmic and anesthetic effects. It is a medication that at high doses produces serious adverse effects. Therefore, you should always follow the doctor's instructions and not self-medicate.

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