Description
Procaine is a local anesthetic with a para-amino function. Sensitization mainly concerns medical, dental
and veterinary professions.
Chemical Properties
The hydrochloride salt
of 2-(diethylamino) ethyl p-aminobenzoate (C13H21ClN2O2
or N2C6H4COOCH2CH2NH(C2H5)2HCl) is generally
referred to as procaine. Although the PABA ester is insoluble in water, the
hydrochloride salt is very soluble in water.
Uses
Procaine (Novocain) is mainly used in dental or medical
procedures requiring infiltration anesthesia, peripheral
block, or spinal block.
Uses
Procaine is a sodium channel blocker and inhibitor of a variety of processes.
Definition
ChEBI:Procaine is a benzoate ester, formally the result of esterification of 4-aminobenzoic acid with 2-diethylaminoethanol but formed experimentally by reaction of ethyl 4-aminobenzoate with 2-diethylaminoethanol. It has a role as a local anaesthetic, a central nervous system depressant, a peripheral nervous system drug and a drug allergen. It is a benzoate ester, a substituted aniline and a tertiary amino compound. It is functionally related to a 2-diethylaminoethanol and a 4-aminobenzoic acid. It is a conjugate base of a procaine(1+).
brand name
Novocain (Hospira).
Biological Functions
Procaine hydrochloride (Novocain) is readily hydrolyzed
by plasma cholinesterase, although hepatic
metabolism also occurs. It is not effective topically but
is employed for infiltration, nerve block, and spinal
anesthesia. It has a relatively slow onset and short (1
hour) duration of action. All concentrations can be
combined with epinephrine. It is available in dental cartridges
with phenylephrine as the vasoconstrictor.
General Description
Procaine was synthesized in 1904 to address the chemical instabilityof cocaine and the local irritation it produced. The pKa of procaine is 8.9; it has low lipid solubility and the estergroup is unstable in basic solutions. Procaine is available inconcentrations ranging from 0.25% to 10% with pHs adjustedto 5.5 to 6.0 for chemical stability. Procaine is also includedin some formulations of penicillin G to decrease the pain ofintramuscular injection.
Contact allergens
Procaine is a local anesthetic with para-amino function.
Sensitization mainly concerns the medical, dental,
and veterinary professions.
Mechanism of action
The fundamental mechanism of analgesia underlying all local anesthetics is the blockade of neurotransmission via inhibition of sodium channels along nerve fibers. Procaine acts mainly by inhibiting sodium influx through voltage gated sodium channels in the neuronal cell membrane of peripheral nerves. When the influx of sodium is interrupted, an action potential cannot arise and signal conduction is thus inhibited.
Clinical Use
Procaine is very quickly metabolizedin the plasma by cholinesterases and in the liver via ester hydrolysisby a pseudocholinesterase. The in vitroelimination half-life is approximately 60 seconds. Any conditionthat decreases the cholinesterase concentration may increaseexposure to procaine and potential toxicity. Decreasedenzyme activity can be found with genetic deficiency, liverdisease, malignancy, malnutrition, renal failure, burns, thirdtrimester of pregnancy, and following cardiopulmonary bypasssurgery. Ester hydrolysis produces PABA, the compoundresponsible for the allergic reactions common to theester anesthetics. Procaine is not used topically because of itsinability to pass through lipid membranes and finds use as aninfiltration agent for cutaneous or mucous membranes, forshort procedures. Procaine is also used for peripheral nerveblock and as an epidural agent to diagnose pain syndromes.
Side effects
When taken by mouth: It is not known whether procaine is safe when taken by mouth. It can cause some side effects including heartburn, migraines, and a serious condition called systemic lupus erythematosus (SLE). SLE causes a variety of symptoms including joint pain, rashes, lung problems, and many other symptoms.
Synthesis
Experimental steps for synthesis of Procaine: In there-necked flask, add p-nitrobenzoic acid 60g, dimethylbenzene 360g, Diethylaminoethanol 44g, reflux divides water, temperature of reaction 141 ~ 143 ℃, reacts 12 hours; React complete, be cooled to less than 20 ℃, reclaim under reduced pressure dimethylbenzene; Reclaim complete, be cooled to less than 40 DEG C, slowly drip 570g6% dilute hydrochloric acid, after adding, stir 30 minutes, be cooled to 20 ~ 25 ℃, filter, obtain filtrate;Upper step filtrate is added in hydrogenation reaction cauldron, add catalyst Ni powder 15g, with nitrogen replacement 2 times, pass into hydrogen, pressure is 10 standard atmospheric pressures, control temperature of reaction 50 ~ 60 ℃ and carry out hydrogenation, react complete, filter, refined salt 16g is added in filtrate, stirring and dissolving, is cooled to 10 ℃, obtains procaine hydrochloride.
Purification Methods
Procain crystallises as the dihydrate from aqueous EtOH and as the anhydrous material from pet ether or diethyl ether. The latter is hygroscopic. [Beilstein 14 IV 1138.]
