Tetracaine Chloroprocaine

Esters of para-aminobenzoic acid Procaine Chloroprocaine Tetracaine Benoxinate... 

One of the first uses of local anesthetics (LA) for anesthesia was in the late nineteenth century with William Halsted reporting a mandibular block and brachial plexus block using cocaine [37,38]. The chemical structure of local anesthetics in clinical use consists of an aromatic (lipophilic) benzene ring linked to an amino group (hydrophflic) via either an ester or an amide intermediate chain. The intermediate link classifies the local anesthetic as either an ester (procaine, chloroprocaine, tetracaine, and cocaine) or an amide (lidocaine, prilocaine, mepivacaine, bupi-vacaine, etidocaine, and ropivacaine). 

Some other anesthetics with similar structures are prilocaine, tetracaine, ropivacaine, bupivacaine, chloroprocaine, and mepivacaine ... 

Tetracaine Tetracaine, the 2-diethylaminoethyl ester of 4-butylaminobenzoic acid (2.1.6), is also structurally analogous to procaine, in which the amino group of the benzene ring is replaced by a butylamine radical. The methods for its synthesis are the same as the above-mentioned methods for procaine or chloroprocaine, with the exception of using 4-butylaminobenzoic acid in place of 4-aminobenzoic acid. There is also a proposed method of synthesis that comes directly from procaine (2.1.1). It consists on its direct reaction with butyric aldehyde and simultaneous reduction by hydrogen using a palladium on carbon catalyst [6]. 

The metabolic degradation of local anesthetics depends on whether the compound has an ester or an amide linkage. Esters are extensively and rapidly metabolized in plasma by pseudochoUnesterase, whereas the amide linkage is resistant to hydrolysis. The rate of local anesthetic hydrolysis is important, since slow biotransformation may lead to drug accumulation and toxicity. In patients with atypical plasma cholinesterase, the use of ester-linked compounds, such as chloroprocaine, procaine and tetracaine, has an increased potential for toxicity. The hydrolysis of all ester-linked local anesthetics leads to the formation of paraaminobenzoic acid (PABA), which is known to be allergenic. Therefore, some people have allergic reactions to the ester class of local anesthetics. 

Ester linked local anaesthetics e.g. cocaine, procaine, tetracaine, benzocaine, chloroprocaine. 

The choice of local anesthetic for infiltration, peripheral nerve blocks, and central neuraxis (spinal/epidural) blockade is usually based on the duration of action required. Procaine and chloroprocaine are short-acting lidocaine, mepivacaine, and prilocaine have an intermediate duration of action and tetracaine, bupivacaine, levobupivacaine, and ropivacaine are long-... 

Many more aminobenzoate amino esters were synthesized, and some were developed as local anesthetics. The only ones still of importance are tetracaine, No. 3, and chloropro-caine, No. 1. An examination of the data on the three aminoalkyl p-aminobenzoates (Nos. 1, 2, and 3, Table 13-6) illustrates some classic. SARs within that series. For example, the o-chloro atom of chloroprocaine would predictably enhance the ester groups instability as exemplified by a four-fold faster rate of hydrolysis—and therefore inactivation (15-fold when compared with tetracaine). The partition coefficients indicate a 570 times greater... 

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