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Lidocaine
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Lidocaine (INN) or lignocaine (former BAN) 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, and in minor surgery.
caine, the first amino amide-type local anesthetic, was first synthesized under the name xylocaine by Swedish chemist Nils Löfgren in 1943.
His colleague Bengt Lundqvist made the first injection anesthesia experiments on himself.It was first marketed in 1948.
caine may be prepared in two steps by the reaction of 2,6-xylidine with chloroacetyl chloride, followed by the reaction with diethylamine:
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caine is approximately 90% metabolized (de-ethylated) in the liver by CYP1A2 (and to a minor extent CYP3A4) to the pharmacologically-active metabolites monoethylglycinexylidide and glycinexylidide.
The elimination half-life of lidocaine is approximately 1.5–2 hours in most patients.

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Encyclopedia
Lidocaine (INN) or lignocaine (former BAN) 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, and in minor surgery.
History
Lidocaine, the first amino amide-type local anesthetic, was first synthesized under the name xylocaine by Swedish chemist Nils Löfgren in 1943.
His colleague Bengt Lundqvist made the first injection anesthesia experiments on himself.It was first marketed in 1948.
Preparation
Lidocaine may be prepared in two steps by the reaction of 2,6-xylidine with chloroacetyl chloride, followed by the reaction with diethylamine:
-
Pharmacokinetics
Lidocaine is approximately 90% metabolized (de-ethylated) in the liver by CYP1A2 (and to a minor extent CYP3A4) to the pharmacologically-active metabolites monoethylglycinexylidide and glycinexylidide.
The elimination half-life of lidocaine is approximately 1.5–2 hours in most patients. This may be prolonged in patients with hepatic impairment (average 343 minutes) or congestive heart failure (average 136 minutes).
Pharmacodynamics
Anesthesia
Lidocaine alters depolarization in neurons, by blocking the fast voltage gated sodium (Na+) channels in the cell membrane. With sufficient blockade, the membrane of the presynaptic neuron will not depolarize and so fail to transmit an action potential, leading to its anaesthetic effects.
Careful titration allows for a high degree of selectivity in the blockage of sensory neurons, whereas higher concentrations will also affect other modalities of neuron signaling.
Clinical use
Indications
Topical lidocaine has been shown to relieve postherpetic neuralgia in some patients, though there is not enough study evidence to recommend it as a first-line treatment. It also has uses as a temporary fix for tinnitus. Although not completely curing the illness, it has been shown to reduce the effects by around two thirds.
Contraindications
Contraindications for the use of lidocaine include:
Adverse drug reactions
Adverse drug reactions (ADRs) are rare when lidocaine is used as a local anesthetic and is administered correctly. Most ADRs associated with lidocaine for anesthesia relate to administration technique (resulting in systemic exposure) or pharmacological effects of anesthesia, but allergic reactions can rarely occur..
Systemic exposure to excessive quantities of lidocaine mainly result in central nervous system (CNS) and cardiovascular effects – CNS effects usually occur at lower blood plasma concentrations and additional cardiovascular effects present at higher concentrations, though cardiovascular collapse may also occur with low concentrations. CNS effects may include CNS excitation (nervousness, tingling around the mouth, tinnitus, tremor, dizziness, blurred vision, seizures) followed by depression, and with increasingly heavier exposure: drowsiness, loss of consciousness, respiratory depression and apnoea). Cardiovascular effects include hypotension, bradycardia, arrhythmias, and/or cardiac arrest – some of which may be due to hypoxemia secondary to respiratory depression.
ADRs associated with the use of intravenous lidocaine are similar to toxic effects from systemic exposure above. These are dose-related and more frequent at high infusion rates (=3 mg/minute). Common ADRs include: headache, dizziness, drowsiness, confusion, visual disturbances, tinnitus, tremor, and/or paraesthesia. Infrequent ADRs associated with the use of lidocaine include: hypotension, bradycardia, arrhythmias, cardiac arrest, muscle twitching, seizures, coma, and/or respiratory depression.
Insensitivity to lidocaine
Relative insensitivity to lidocaine runs in families. In hypokalemic sensory overstimulation, relative insensitivity to lidocaine has been described in people who also have attention deficit hyperactivity disorder. In dental anesthesia, a relative insensitivity to lidocaine can occur for anatomical reasons due to unexpected positions of nerves.
Dosage forms
Lidocaine, usually in the form of lidocaine hydrochloride, is available in various forms including:
- Injected local anesthetic (sometimes combined with epinephrine)
- Dermal patch (sometimes combined with prilocaine)
- Intravenous injection (sometimes combined with epinephrine)
- Intravenous infusion
- Nasal instillation/spray (combined with phenylephrine)
- Oral gel (often referred to as "viscous lidocaine" or abbreviated "lidocaine visc" or "lidocaine hcl visc" in pharmacology; used as teething gel)
- Oral liquid
- Topical gel (as with Aloe Vera gels that include Lidocaine)
- Topical liquid
- Topical patch (Lidocaine 5% patch is marketed as "Lidoderm" in the US (since 1999) and "Versatis" in the UK (since 2007 by Grünenthal))
- Topical aerosol Spray
Additive in cocaine
Lidocaine is often added to cocaine as a diluent. Cocaine numbs the gums when applied, and since lidocaine causes stronger gingival numbness, users get the impression of high-quality cocaine when in actuality, the user is receiving a diluted product.
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