Local anesthetic:
Local anesthetics are widely used in dentistry for different procedures and are chemical substances that block nerve conduction, temporarily and irreversibly in order to avoid pain and are placed in specific sites of the body, for example in oral tissues.
Pharmacology of local anesthetics related to effectiveness and safety
Latency time It is defined as the time that elapses between the infiltration of the anesthetic substance in the tissue until the first signs of insensibility are felt. It is influenced by the distance of the route the anesthetic must travel, with the ability to cross the membrane of the nerve cells.
Duration of the anesthetic effect Also known as the duration of the action, related to the capacity of fixation of the anesthetic substance to the nerve cell proteins and with lipid solubility.
pH of anesthetics It is one of the factors that influence the action of blocking nerve conduction, and is the factor that conditions the movement of the anesthetic from the site where it is administered to the nerve fiber, that is why the tissues that are infected make the effectiveness is decreased, since the pH would turn acidic. In addition, the pH varies according to whether or not it has a vasoconstrictor.
Power Anesthetic capacity to pass the lipids of the nerve membranes, the greater the liposolubility, the greater the anesthetic power, depending on how the power is the classification of the action time, low power with short action, intermediate power with action medium and high power with long action.
Diffusion It is related to the minimum concentration required to inhibit nerve conduction, given by the transfer of molecules or ions from an anesthetic solution from the point where it infiltrates to the membrane of the nerve cell.
Articaine
Articaine is a short-acting local anesthetic, belonging to the group of amides, it has an additional ester group that is rapidly hydrolyzed by plasma esterases, which exhibits a lower toxicity compared to other drugs of the same family. This dissolves better than other amides in the soft tissues and bone, for this reason, it is especially indicated for dental use.
Articaine is introduced in 1972 in the market of local anesthetics. Prepared for the first time by Rusching et al in 1969, it changed its generic name to articaine when it began to be used in clinical practice in Germany in 1976. Its use gradually expanded, until it entered the market of the United States and Canada, in 1983 and in the United Kingdom in 1998.
Articaine with vasoconstrictor (epinephrine) is administered submucosally. The onset of anesthetic effects is observed between 1 to 6 minutes and the duration of anesthesia is approximately one hour and is recommended for long procedures. After administration, maximum concentrations are reached after 20 minutes, approximately between 60 and 80% bind plasma proteins, in particular albumin and gamma globulins, and are easily distributed in soft tissues.
Its main metabolite is the articainic acid, which is metabolized by the isoenzymes of the cytochrome P450, between 5 and 10% of the articainic acid; this causes the increase of the elimination, half-life to 90 minutes. The drug is eliminated in the urine as articainic acid, as glucuronide of the articainic acid and as articaine without metabolizing.
The administration of vasoconstrictors such as epinephrine, together with an anesthetic, could cause increases in blood pressure or heart rate due to higher plasma levels, however, these adverse effects are uncommon.
Patients receiving local anesthesia for dental treatments may experience side effects at the level of the Central Nervous System (CNS), in case of receiving an intra-arterial injection with reflux into the cerebral circulation. Patients with peripheral vascular diseases and hypertension may experience an exaggerated response when treated with articaine-epinephrine due to the vasoconstrictive effects of epinephrine, which can be especially intense in the elderly.
Because of its bisulfite content (as a preservative of epinephrine), the preparations of articaine-epinephrine are contraindicated in patients with hypersensitivity to bisulfite. In addition, patients with asthma are usually more susceptible than others to this hypersensitivity.
There are few studies evaluating the pharmacokinetics of articaine in the elderly or in patients with renal or hepatic insufficiency, although caution is advised when administering articaine-epinephrine to patients with liver diseases, as these patients are more susceptible to the drug's potential toxicity and Dose reductions may be necessary. It should also be administered with caution in patients with a history of drug abuse because the adverse reactions are dose-related and in elderly patients should be dosed with the minimum effective dose.
