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Many local anesthetics fall into two general chemical classes, amino esters (top) and amino amides (bottom). A local anesthetic (LA) is a medication that causes absence of all sensation (including pain) in a specific body part without loss of consciousness, [1] providing local anesthesia, as opposed to a general anesthetic, which eliminates all sensation in the entire body and causes ...
Local anesthetics can be either ester- or amide-based. Ester local anesthetics are generally unstable in solution and fast-acting, are rapidly metabolised by cholinesterases in the blood plasma and liver, [4] and more commonly induce allergic reactions. Amide local anesthetics are generally heat-stable, with a long shelf life (around two years).
Structurally, amino esters consist of three molecular components: a lipophilic part (ester); an intermediate aliphatic chain; a hydrophilic part (amine); The chemical linkage between the lipophilic part and the intermediate chain can be of the amide-type or the ester-type, and is the general basis for the current classification of local anesthetics.
ester- benzoic ambucaine [1] diester - aminosalicylic articaine: Astracaine, Septanest, Septocaine, Ultracaine, Zorcaine Amide benzocaine: Anbesol, Orajel Ester - Aminobenzoic Short benzonatate: Tessalon bupivacaine: Marcaine, Sensorcaine, Vivacaine 1957 (Ekenstam) 1963 (Widman and Telivuo) Amide Moderate butacaine: ester- aminobenzoic ...
Like lidocaine, bupivacaine is an amino-amide anesthetic; the aromatic head and the hydrocarbon chain are linked by an amide bond rather than an ester as in earlier local anesthetics. As a result, the amino-amide anesthetics are more stable and less likely to cause allergic reactions.
E.g. of amide LA: lidocaine, prilocaine, articaine, mepivacaine; E.g. of ester LA: benzocaine, procaine; Genuine allergic reactions of an amide LA is very uncommon. An ester LA is more possible to result in an allergic reaction because the compound will be broken down to para-aminobenzoic acid (PABA) which is a trigger for allergic reactions. [30]
Articaine is a dental amide-type local anesthetic. It is the most widely used local anesthetic in a number of European countries [2] and is available in many countries. It is the only local anaesthetic to contain a thiophene ring, meaning it can be described as 'thiophenic'; this conveys lipid solubility. [3]
Amides do not readily participate in nucleophilic substitution reactions. Amides are stable to water, and are roughly 100 times more stable towards hydrolysis than esters. [ citation needed ] Amides can, however, be hydrolyzed to carboxylic acids in the presence of acid or base.