Composition of Local Anesthesia – LA with Vasoconstrictor and Plain LA

The Local Anesthesia consists of different components and the whole composition of local anesthesia is made in a way that is is very efficient in producing an anaesthetic effect and increase the numbness in the patients who have got several medical conditions but wanted to get a dental treatment done. Check below for the entire list of components of the local anesthesia.

Composition of Local Anesthesia

The main components that are included in the local anesthesia solution include:

  • LA Drug (primarily Lignocaine)
  • Vasoconstrictor (primarily Adrenaline)
  • Preservatives
  • Ringers Solution
  • Distilled Water

Local anesthesiaA few points to remember before you learn about the role of each component in the solution:

  • The preservatives that are added, are not just for preserving the solution from the micro-organisms, but there are preservatives which can keep the vasoconstrictor from from oxidant by acting as an anti-oxidant.
  • Selection of the LA solution is based on the condition a patient is in, and if the patient has got a heart trouble or suffering from high blood pressure / hypertension.
  • The composition that is given below has mixed content from the books – Local Anesthesia by Monheims, and Manual of Local Anesthesia in Dentistry by AP Chitre.

What is Plain LA? Plain Local anesthesia is something which doesn’t have the vasoconstrictor in it, and thus it only has got the local anesthetic drug, and it is a suitable one for the hypertensive and heart patients.

Local Anesthesia Components and Roles

Local Anesthesia Drug – Lignocaine Hydrochloride

This comes as a percentage in the solution, and when it means that the Lignox is coming with 2% lignocaine, it means that 20ml of the solution would have 4ml of Lignocaine, and the most of the other liquid is water, the main solvent.

This is the component that provides the numbness and the anesthetic effect to the tissue and the teeth which are to be treated, based on the area and the nerves that are injected. The solution is very stable and it is autoclavable for being sterilized before injecting into the patient’s tissues, and the solution comes in different ratios along with the vasoconstrictor.

Lignocaine is not the only drug which acts as a local anesthetic agent, but in India it is one of the most frequently used one.

Vasoconstrictor / Vasopressor – Adrenaline Bitartarate

The vasoconstrictor in the LA solution is responsible for making the drug act longer and also in preventing much bleeding, as it helps in constrictions of the blood vessels when the treatment is being done. The vasoconstrictor used in the solution is Adrenaline bitartarate, which comes in different ratios compared to the anesthetic drug, and the various ratios are like 1:80000, 1:100000, 1:180000, 1:200000 etc.

The vasoconstrictor has a few functions such as increasing the safety of the local anesthesia solution, making the action of the local anesthetic longer and also helping in controlling the bleeding. Although it has got so many properties, the local anesthetic is prone to oxidation when the bottle is exposed open for sometime, and thus the adrenaline would get biodegraded because of the oxygen, and to prevent this from happening, the LA solutions have the preservative which acts as anti-oxidants. The most common anti-oxidant used is Sodium Bisulfite.

Again, there are people who are allergic to bisulfites too, thus in the pre-anesthetic medical evaluation, this point has to be taken note of, and the patient should be tested for the allergy before proceeding with the usage of the LA solution having the preservative for vasoconstrictor.

Ringer’s Solution

This is not seen in all the anesthetic solutions that are available around, but where it is a part of the composition, the Ringers solution helps in making the solution isotonic. The Ringer’s solution consists of the Sodium Chloride (NaCl), and it prevents the hypertensive nature of the solution which could have caused edema, paresthesia to the tissues.

Preservatives – Methyl Paraben, Thymol and Chlorbutol

The above named are a few preservatives that are used to keep the solution with a longer shelf life. The Methylparaben has got a bacteristatic and antifungal property, while the Thymol has antiseptic, Antifungal and also an anti-inflammatory action.

* The usage of methylparaben in the LA solution was banned in US after it was reported to be allergic, but it is still used in the LA solutions in India and other eastern countries.

Water – Solvent

Water is the main solvent and the major component in the Local anesthetic solution, which mixes all the above components.

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