Prilocaine

Chemical properties

White or almost white, crystalline powder.

The Uses of Prilocaine

Prilocaine, known by the synonyms Citanest and Xylonest, is a pharmaceutical agent that has pharmacological parameters comparable to those of lidocaine. Despite this similarity, prilocaine is rarely used in medical practice due to its potential toxic manifestations.

Background

A local anesthetic that is similar pharmacologically to lidocaine. Currently, it is used most often for infiltration anesthesia in dentistry. (From AMA Drug Evaluations Annual, 1992, p165)

Indications

Used as a local anaesthetic and is often used in dentistry.

Definition

ChEBI: An amino acid amide in which N-propyl-DL-alanine and 2-methylaniline have combined to form the amide bond; used as a local anaesthetic.

brand name

lidocaine/prilocaine topical
Brand names: Emla, LiproZonePak, Dolotranz, Livixil Pak, and Anodyne LPT.

General Description

Prilocaine hydrochloride is a water-soluble salt that is available as a solution for various medical applications, including nerve block or infiltration in dental procedures. It is also utilized for intravenous regional anesthesia, where its low risk of central nervous system (CNS) toxicity is attributed to its rapid metabolism. In its crystalline form, Prilocaine is a key component of the EMLA cream, which is used topically to reduce the pain associated with needle sticks, particularly in children.

Prilocaine solutions are available in various concentrations, up to 4%, and can be found with or without epinephrine and with or without preservatives. It is important to note that a 4% Prilocaine solution should be protected from light to maintain its quality. The manufacturer advises discarding the solution if it changes color, turning pinkish or darker than a light yellow, indicating potential degradation.

Pharmacokinetics

Prilocaine functions by binding to the intracellular surface of sodium channels, thereby blocking the influx of sodium into the cell. This action prevents the propagation of action potentials and nerve function. Importantly, this block is reversible; once the drug diffuses away from the cell, the function of the sodium channels is restored, allowing nerve propagation to return to normal.

Pharmacology

Prilocaine is less toxic than lidocaine, with a high clearance, attributable to metabolism in the lungs, kidneys and liver. It is associated with methaemoglobinaemia at doses >600mg. It is sometimes used at a concentration of 0.5% for the provision of intravenous regional anaesthesia, and a combination of prilocaine 3% with felypressin is available for low-volume local infiltration anaesthesia in dental surgery. A 2% formulation is also available for spinal anaesthesia. Prilocaine is also formulated in a eutectic mixture with lidocaine (EMLA) for topical anaesthesia.

Clinical Use

Prilocaine metabolism has beenstudied extensively in animal models, less is known aboutthe human metabolites or the human CYP enzymes involvedin their formation . The metabolism of prilocainein the liver yields o-toluidine, which is a possiblecarcinogen. Many aromatic amines, including o-toluidinehave been shown to be mutagenic, and metabolites of otoluidinehave been shown to form DNA adducts.Metabolites of o-toluidine are also believed to be responsiblefor the methemoglobinemia observed with prilocaineuse. To decrease the potential for methemoglobinemia, strictadherence to the maximum recommended dose should befollowed. Metabolism of prilocaine is extensive with lessthan 5% of a dose excreted unchanged in the urine.

Synthesis

Prilocaine, 2-(propylamino)-o-propiontoluidine (2.2.14), is structurally related to the exact same group as ethidocaine, yet it differs structurally in that during synthesis, o-toluidine is used instead of 2,6-dimethylaniline, and instead of a butyric acid, a fragment of propionic acid, and a terminal propylethylamine group is replaced with a propylamine group. In order to synthesize prilocaine, o-toluidine is reacted with bromopropionyl bromide, and the resulting bromopropionyltoluidide (2.2.13) is then reacted with propylamine, which gives prilocaine [22,23].

Metabolism

Not Available