Lidocaine

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Lidocaine
Clinical data
Pregnancy
category
  • AU: A
Routes of
administration		IV, subcutaneous, topical
ATC code
Legal status
Legal status
  • AU: S4 (Prescription only)
  • US: unregulated
Pharmacokinetic data
Bioavailability35% (oral)
3% (topical)
MetabolismHepatic, 90% CYP1A2-mediated
Elimination half-life1.5–2 hours
Excretionrenal
Identifiers
  • 2-(diethylamino)-
    N-(2,6-dimethylphenyl)acetamide
CAS Number
PubChem CID
DrugBank
CompTox Dashboard (EPA)
ECHA InfoCard100.004.821 Edit this at Wikidata
Chemical and physical data
FormulaC14H22N2O
Molar mass234.34 g/mol g·mol−1
3D model (JSmol)
Melting point68 °C (154 °F)
  • CCN(CC)CC(=O)Nc1c(C)cccc1C

Lidocaine (INN) (Template:PronEng) or lignocaine (former BAN) (/ˈlɪgnoʊkeɪn/) 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 Nils Löfgren in 1943.[1] His colleague Bengt Lundqvist made the first injection anesthesia experiments on himself.[1]It was first marketed in 1948.

Pharmacokinetics

Lidocaine is approximately 90% metabolized 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). (Thomson et al., 1973)

Pharmacodynamics

Anesthesia

Lidocaine alters depolarization in neurons, by blocking the fast voltage gated sodium (Na+) channels in the cell membrane[2]. With sufficient blockade, the membrane of the presynaptic neuron will not depolarize and so fail to transmit an action potential, leading to its anesthetic 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, although there is not enough study evidence to recommend it as a first-line treatment. (Khaliq et al., 2007)

Intravenous or intraosseous lidocaine is used to blunt the effects of laryngoscopy during rapid sequence intubation procedures, especially in cases of head injury.[citation needed]

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.[citation needed].

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. (Rossi, 2006)

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. (Rossi, 2006)

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))
  • Topica. aerosol Spray

Notes

  1. ^ a b Nils Löfgren (1948). Xylocaine: a new synthetic drug. {{cite book}}: Unknown parameter |address= ignored (|location= suggested) (help); Unknown parameter |note= ignored (help)
  2. ^ Cattterall WA (2002). "Molecular mechanisms of gating and drug block of sodium channels". Novartis Found Symp. 241: 206–32. doi:10.1002/0470846682.ch14. PMID 11771647.

References

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