Chloroprocaine (often in the hydrochloride salt form as the aforementioned trade names) is a local anesthetic

Local anesthetic

A local anesthetic is a drug that causes reversible local anesthesia, generally for the aim of having local analgesic effect, that is, inducing absence of pain sensation, although other local senses are often affected as well...

 given by injection

Injection (medicine)

An injection is an infusion method of putting fluid into the body, usually with a hollow needle and a syringe which is pierced through the skin to a sufficient depth for the material to be forced into the body...

 during surgical procedures

Surgery

Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...

 and labor and delivery

Childbirth

Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...

. Chloroprocaine constricts blood vessels resulting in reduced blood loss; this is in contrast to other local anesthetics e.g. lidocaine, which do not do such. Chloroprocaine is an ester anesthetic.

Obstetrics

Amide-linked local anesthetic agents, such as lidocaine

Lidocaine

Lidocaine , Xylocaine, or lignocaine is a common local anesthetic and antiarrhythmic drug. Lidocaine is used topically to relieve itching, burning and pain from skin inflammations, injected as a dental anesthetic or as a local anesthetic for minor surgery.- History :Lidocaine, the first amino...

 and bupivacaine

Bupivacaine

Bupivacaine is a local anaesthetic drug belonging to the amino amide group. AstraZeneca commonly markets it under various trade names, including Marcain, Marcaine, Sensorcaine and Vivacaine.-Indications:...

, can become "trapped" in their ionized forms on the fetal side of the placenta

Placenta

The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

, and therefore their net transfer across the placenta is increased. An ester-linked local anesthetic agent, 2-chloroprocaine, is rapidly metabolized, and placental transfer is limited. Since the metabolism of 2-chloroprocaine by fetal plasma is slower than in maternal plasma, the potential for ion trapping exists. Fetal pH is slightly lower than maternal (7.32 to 7.38), thus most unionized drugs are "ion trapped" to a degree, even in a healthy fetus. Chloroprocaine (pKa 8.7) is the drug of choice for epidural

Epidural

The term epidural is often short for epidural analgesia, a form of regional analgesia involving injection of drugs through a catheter placed into the epidural space...

 analgesia and a decompensating fetus, because it does not participate in ion trapping. Placental transfer of 2-chloroprocaine is not influenced by fetal acidosis.

In vitro half-life

Half-life

Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 of Chloroprocaine is 21 seconds for maternal and 43 seconds for fetal blood. In patients who are homozygous atypical for plasma cholinesterase, Chloroprocaine typically exists for two minutes in circulation.

Chloroprocaine should rarely be used in the subarachnoid space because of the risk of adhesive arachnoiditis. This is likely related to the preservative sodium bisulfate

Sodium bisulfate

Sodium bisulfate, also known as sodium hydrogen sulfate , is an acid salt. It is a dry granular product that can be safely shipped and stored. The anhydrous form is hygroscopic. Solutions of sodium bisulfate are acidic, with a 1M solution having a pH of Sodium bisulfate, also known as sodium...

. It is also not used in IV regional anesthesia due to the risk of thrombophlebitis

Thrombophlebitis

Thrombophlebitis is phlebitis related to a thrombus . When it occurs repeatedly in different locations, it is known as "Thrombophlebitis migrans" or "migrating thrombophlebitis".-Signs and symptoms:...

.

Chemistry

Synthesis of this drug is accomplished by directly reacting the hydrochloride of the 4-amino-2-chlorbenzoic acid chloride with the hydrochloride of 2-diethylaminoethanol. The hydrochloride of 4-amino-2-chlorbenzoic acid chloride needed for synthesis is synthesized by reacting 2-chloro-4-aminobenzoic acid with thionyl chloride

Thionyl chloride

Thionyl chloride is an inorganic compound with the formula SOCl2. It is a reactive chemical reagent used in chlorination reactions. It is a colorless, distillable liquid at room temperature and pressure that decomposes above 140 °C. Thionyl chloride is sometimes confused with sulfuryl...

.

• H.C. Marks, H.I. Rubin, (1949).