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Chloroprocaine (N,N′-diethylaminoethyl 4-amino-2-chlorobenzoate) is a very short-acting, amino ester-type local anesthetic used to provide regional anesthesia by infiltration as well as by peripheral and central nerve block, including lumbar and caudal epidural blocks. The presence of a chlorine atom ortho to the carbonyl of the ester function increases its rate of hydrolysis by plasma cholinesterase at least threefold compared to procaine and benzocaine. Thus, chloroprocaine may be used in maternal and neonatal patients with minimal placental passage of chloroprocaine. The lower plasma cholinesterase activity in the maternal epidural space must still have sufficient activity for degrading chloroprocaine and, thus, not allowing it to cross the placenta barrier. Like PABA, the hydrolysis product of chloroprocaine, 4-amino-2-chlorobenzoic acid, also inhibits the action of sulfonamides. Therefore, its use with sulfonamides should be avoided.

Anesthetic (local).

Chloroprocaine is an ester that is metabolised rapidly by ester hydrolysis, so its duration of action is short and potential for cardiac toxicity relatively low. It can be used as a preservative-free solution for spinal anaesthesia for surgical procedures up to 40 min in duration.

ChEBI: Procaine in which one of the hydrogens ortho- to the carboxylic acid group is substituted by chlorine. It is used as its monohydrochloride salt as a local anaesthetic, particularly for oral surgery. It has the advantage over lidocaine of const icting blood vessels, so reducing bleeding.

Nesacaine (Abraxis).

Chloroprocaine hydrochloride (Nesacaine) is obtained from addition of a chlorine atom to procaine, which results in a compound of greater potency and less toxicity than procaine itself. This local anesthetic is hydrolyzed very rapidly by cholinesterase and therefore has a short plasma half-life. Because it is broken down rapidly, chloroprocaine is commonly used in obstetrics. It is believed that the small amount that might get to the fetus continues to be rapidly hydrolyzed, so there may be no residual effects on the neonate.

The 2 chloride substitution on the aromatic ring of chloroprocaineis an electron-withdrawing functional group. Thus, itpulls the electron density from the carbonyl carbon into thering. The carbonyl carbon is now a stronger electrophile andmore susceptible to ester hydrolysis. Therefore, chloroprocainehas a more rapid metabolism than procaine. The in vitroplasma half-life is approximately 25 seconds. The 2-chloro-4-aminobenzoic acid metabolite precludes this from being usedin patients allergic to PABA. The very short duration of actionmeans that this drug can be used in large doses for conductionblock (with rapid onset and short duration of action.).

Chloroprocaine is used for cutaneous or mucous membraneinfiltration for surgical procedures, epidural anesthesia(without preservatives) and for peripheral conduction block.