Lidocaine Hydrochloride

Local Anesthetic (Amide type) Sodium Channel Blocker / Class IB Antiarrhythmic

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog IV (bolus) 2-4 mg/kg (slow IV) Given slowly over 2-3 minutes, may repeat once after 5-10 minutes if needed Duration: For acute arrhythmia management
Notes: Follow with CRI if continuous effect needed.
Dog IV (CRI) 25-80 mcg/kg/min (0.025-0.08 mg/kg/min) Continuous infusion Duration: As needed for arrhythmia or pain management
Notes: Start at lower end and titrate to effect. Monitor for signs of toxicity.
Dog Local infiltration 1-2 mg/kg (maximum total dose) Single administration Duration: For local anesthesia
Notes: Use lower doses in small dogs. Can be combined with epinephrine (1:100,000) to prolong effect.
Cat IV (bolus) 0.25-0.75 mg/kg (slow IV) Given slowly, may repeat once after 5-10 minutes if needed Duration: For acute arrhythmia management
Notes: Cats are more sensitive to CNS effects; use lower doses.
Cat IV (CRI) 10-40 mcg/kg/min (0.01-0.04 mg/kg/min) Continuous infusion Duration: As needed for arrhythmia or pain management
Notes: Use lower doses than dogs; monitor closely.
Cat Local infiltration 1 mg/kg (maximum total dose) Single administration Duration: For local anesthesia
Notes: Use lower doses due to increased sensitivity.
Horse IV (bolus) 0.5-1.5 mg/kg (slow IV) Given slowly, may repeat once after 5-10 minutes if needed Duration: For acute arrhythmia management
Notes: Monitor ECG and blood pressure.
Horse IV (CRI) 30-50 mcg/kg/min (0.03-0.05 mg/kg/min) Continuous infusion Duration: As needed for arrhythmia or pain management
Notes: Titrate to effect; monitor for ataxia and muscle tremors.
Horse Local infiltration 2-4 mg/kg (maximum total dose) Single administration Duration: For local anesthesia
Notes: Commonly used for nerve blocks; avoid exceeding maximum dose.
Cattle Local infiltration 2-4 mg/kg (maximum total dose) Single administration Duration: For local anesthesia
Notes: Commonly used for dehorning, castration, and other procedures.
Cattle Epidural 0.2-0.4 mg/kg (as 2% solution) Single administration Duration: For obstetrical procedures
Notes: Volume depends on size; use aseptic technique.
Small Ruminants Local infiltration 2-4 mg/kg (maximum total dose) Single administration Duration: For local anesthesia
Notes: Use lower doses in smaller animals.
Rabbit Local infiltration 1-2 mg/kg (maximum total dose) Single administration Duration: For local anesthesia
Notes: Rabbits are sensitive; use lower doses.
Bird/Poultry Local infiltration 1-2 mg/kg (maximum total dose) Single administration Duration: For local anesthesia
Notes: Use with caution; birds are sensitive to lidocaine.
Exotic/Other Local infiltration 1-2 mg/kg (maximum total dose) Single administration Duration: For local anesthesia
Notes: Dose depends on species; consult specific references.

Clinical Indications & Species Uses

General Indications
  • Local and regional anesthesia
  • Treatment of ventricular arrhythmias
  • Topical anesthesia for mucous membranes
  • Adjunct in pain management (CRI)
Dog (Canine)
  • Local and regional anesthesia (infiltration, nerve blocks, epidural)
  • Treatment of ventricular arrhythmias (e.g., ventricular tachycardia, premature ventricular contractions)
  • Topical anesthesia for mucous membranes (e.g., oral, ophthalmic)
  • Adjunct in pain management (e.g., constant rate infusion for analgesia)
Cat (Feline)
  • Local and regional anesthesia (infiltration, nerve blocks, epidural)
  • Treatment of ventricular arrhythmias (less commonly used than in dogs)
  • Topical anesthesia for mucous membranes
  • Adjunct in pain management (CRI)
Horse (Equine)
  • Local and regional anesthesia (e.g., nerve blocks for lameness evaluation, epidural)
  • Treatment of ventricular arrhythmias (e.g., ventricular tachycardia)
  • Topical anesthesia for eye procedures (corneal anesthesia)
Cattle (Bovine)
  • Local anesthesia for surgical procedures (e.g., dehorning, castration, C-section)
  • Epidural anesthesia for obstetrical procedures
  • Treatment of ventricular arrhythmias (rarely used)
Small Ruminants (Sheep / Goat)
  • Local anesthesia for surgical procedures (e.g., dehorning, castration)
  • Epidural anesthesia for obstetrical procedures
Rabbit & Small Mammals
  • Local anesthesia for minor procedures (infiltration, nerve blocks)
  • Topical anesthesia for ophthalmic procedures
Avian & Poultry
  • Local anesthesia for minor surgical procedures (e.g., feather follicle removal, wound repair)
Exotic & Other Species
  • Local anesthesia in reptiles (e.g., for skin biopsies, minor surgery)
  • Local anesthesia in small mammals (e.g., guinea pigs, rats) for minor procedures

Pharmacology & Mechanism of Action

Drug Class: Local Anesthetic (Amide type) | Pharmacological Group: Sodium Channel Blocker / Class IB Antiarrhythmic

Mechanism of Action: Lidocaine reversibly blocks voltage-gated sodium channels in nerve cell membranes, preventing the transient increase in permeability to sodium that is necessary for the initiation and conduction of action potentials. This action is use-dependent, meaning it preferentially binds to channels in the inactivated state, which is more frequent during rapid firing. In the heart, lidocaine primarily affects fast-response Purkinje fibers and ventricular muscle, decreasing automaticity and increasing the electrical stimulation threshold for ventricular fibrillation. It also shortens the action potential duration and effective refractory period, particularly in ischemic tissue, and suppresses re-entrant arrhythmias.

Pharmacodynamics: Lidocaine produces local anesthesia by blocking nerve impulse conduction. Its onset of action is rapid (within 1-2 minutes for infiltration) and duration is moderate (1-2 hours, depending on dose and use of vasoconstrictor). Systemically, it has antiarrhythmic effects, primarily on ventricular arrhythmias, with minimal effect on atrial tissue. It also has analgesic, anti-inflammatory, and antimicrobial properties when used topically or locally. At high doses, it can cause central nervous system (CNS) stimulation followed by depression, and cardiovascular depression.

⚑ Pharmacokinetics Summary

Absorption: Lidocaine is well absorbed from the gastrointestinal tract, but undergoes extensive first-pass hepatic metabolism, reducing oral bioavailability to about 30%. It is also well absorbed from mucous membranes and damaged skin. Absorption from subcutaneous or intramuscular injection is rapid, with peak plasma concentrations occurring within 5-15 minutes. The addition of epinephrine slows absorption and prolongs local effect.
Distribution: Lidocaine is widely distributed throughout the body, with a volume of distribution of about 1-2 L/kg in dogs and cats. It crosses the blood-brain barrier and placenta. It is approximately 60-80% protein-bound, mainly to alpha-1-acid glycoprotein. Distribution is rapid to highly perfused organs (brain, heart, liver, kidneys) and then to muscle and adipose tissue.
Metabolism: Lidocaine is extensively metabolized in the liver, primarily by oxidative N-deethylation to monoethylglycinexylidide (MEGX) and glycinexylidide (GX), which have antiarrhythmic and proconvulsant activity. The metabolism is rapid, with hepatic extraction ratio high. In animals with hepatic dysfunction, metabolism is reduced, increasing the risk of toxicity.
Excretion: Less than 10% of lidocaine is excreted unchanged in the urine. The metabolites are excreted renally, with about 70-80% of the dose appearing in urine as metabolites. Biliary excretion also occurs. The elimination half-life is short, approximately 1-2 hours in dogs and cats, but may be prolonged in neonates or animals with hepatic or cardiac disease.
Half-Life: Dogs: 1-2 hours; Cats: 1-1.5 hours; Horses: 1-2 hours; Cattle: 1-2 hours
Bioavailability: Oral: ~30% (due to first-pass effect); IV: 100%; Topical: variable, but can be significant if applied to inflamed mucosa
Protein Binding: 60-80% (primarily to alpha-1-acid glycoprotein)

Available Formulations & Strengths

Injectable Solution 0.5%, 1%, 2% (with or without epinephrine) (IV, SC, IM, epidural, local infiltration)
Topical Gel/Ointment 2%, 5% (Topical (mucous membranes, skin))
Ophthalmic Solution 0.5%, 1% (Ophthalmic)
Transdermal Patch 5% (e.g., Lidoderm) (Transdermal (not commonly used in veterinary medicine))

Contraindications & Clinical Warnings

Contraindications:
  • Known hypersensitivity to lidocaine or other amide local anesthetics
  • Severe heart block (second or third degree) without a pacemaker
  • Severe hypotension or cardiogenic shock
  • Myasthenia gravis (relative contraindication)
  • Use of Class I antiarrhythmic agents (e.g., procainamide, quinidine) concurrently (may have additive cardiotoxic effects)
  • Do not use solutions containing epinephrine for intravenous administration or for areas with end-arteries (e.g., ears, tail, digits) due to risk of ischemia
Warnings & Clinical Precautions:
  • Use with caution in animals with hepatic disease, severe renal impairment, or congestive heart failure.
  • Use with caution in neonates, geriatric animals, and debilitated patients.
  • Monitor for CNS toxicity (e.g., muscle twitching, seizures) and cardiovascular effects (e.g., hypotension, arrhythmias) during IV administration.
  • Do not exceed maximum recommended doses; calculate carefully for each patient.
  • When using epidural anesthesia, use preservative-free solutions and ensure proper technique to avoid spinal cord injury.
  • In food animals, observe withdrawal times; lidocaine is not approved for use in food animals in some countries, but extra-label use may be permitted with appropriate withdrawal periods.
  • Topical application to large areas of damaged skin can lead to systemic absorption and toxicity.
  • Use with caution in animals with malignant hyperthermia (though lidocaine is not a trigger, it may be used with caution).

Adverse Effects & Reactions

Common:

  • Local irritation at injection site
  • Transient hypotension
  • CNS depression (drowsiness, ataxia) at high doses
  • Nausea or vomiting (rare in animals)

Serious / Severe:

  • Seizures (CNS toxicity)
  • Cardiac arrhythmias (e.g., bradycardia, AV block, ventricular fibrillation)
  • Cardiovascular collapse
  • Respiratory depression or arrest
  • Methemoglobinemia (especially with topical use in cats and neonates)

Rare:

  • Allergic reactions (urticaria, anaphylaxis)
  • Peripheral neuropathy (with nerve blocks)
  • Epidural or spinal hematoma (with epidural use)
  • Local tissue necrosis (with epinephrine-containing solutions)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Class I antiarrhythmics (e.g., procainamide, quinidine) Additive cardiotoxic effects, increased risk of arrhythmias and hypotension. High
Beta-blockers (e.g., propranolol) Reduced hepatic blood flow, decreased lidocaine metabolism, increased risk of toxicity. Moderate
Cimetidine Inhibits hepatic metabolism of lidocaine, increasing plasma levels and risk of toxicity. Moderate
Phenytoin May have additive cardiac depressant effects; also phenytoin may increase lidocaine metabolism. Moderate
Succinylcholine Lidocaine may potentiate the neuromuscular blocking effects of succinylcholine. Mild
Epinephrine (when combined) Increased risk of hypertension and tachycardia if absorbed systemically; also risk of tissue ischemia if injected into end-artery areas. Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • CNS excitation (restlessness, muscle twitching, tremors, seizures)
  • CNS depression (drowsiness, coma)
  • Cardiovascular effects (bradycardia, hypotension, heart block, cardiac arrest)
  • Respiratory depression
  • Methemoglobinemia (with high doses of topical lidocaine)

Emergency Treatment Protocol: Discontinue administration immediately. Provide supportive care: maintain airway, administer oxygen, and assist ventilation if needed. Control seizures with diazepam or barbiturates (e.g., pentobarbital). Treat cardiovascular depression with IV fluids and vasopressors (e.g., epinephrine, dopamine) as needed. For severe bradycardia or heart block, atropine may be used. In cases of methemoglobinemia, administer methylene blue (1-2 mg/kg IV) if severe. Consider lipid emulsion therapy (e.g., Intralipid 20% at 1.5 mL/kg bolus followed by 0.25 mL/kg/min for 30-60 minutes) for severe cardiotoxicity. Monitor ECG and vital signs closely.

Food Animal Withdrawal Times

πŸ₯© Meat: 3 daysπŸ₯› Milk: 1 days

Withdrawal times are based on label recommendations for approved products. For extra-label use, consult FARAD (Food Animal Residue Avoidance Databank) for specific withdrawal times. In the US, lidocaine is not approved for use in food animals, but extra-label use is permitted under AMDUCA with a valid VCPR; withdrawal times may vary. For cattle, a meat withdrawal of 3 days and milk withdrawal of 1 day are commonly cited for local anesthesia, but confirm with FARAD.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature (20-25Β°C, excursions permitted to 15-30Β°C).

Handling & Special Conditions: Protect from freezing. Keep containers tightly closed. Do not use solutions that are discolored or contain precipitate.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Lidocaine is FDA-approved for use in humans and some veterinary products are approved for local anesthesia in animals (e.g., 2% injectable solution). However, many uses in veterinary medicine are extra-label.

Extra-Label (Off-Label) Use: Lidocaine is a prescription drug. Extra-label use in food animals is permitted under AMDUCA (Animal Medicinal Drug Use Clarification Act) in the US, but requires a valid veterinarian-client-patient relationship and must follow FDA regulations. Withdrawal times must be established by the veterinarian, often with guidance from FARAD. In the EU, similar regulations apply under Cascade.

Clinical Pearls & Practice Notes

πŸ’‘ Clinical Insights: Lidocaine is a versatile drug in veterinary practice, primarily used for local and regional anesthesia, and as a second-line antiarrhythmic for ventricular arrhythmias. It is also increasingly used as a constant rate infusion (CRI) for analgesia and as an adjunct to general anesthesia to reduce inhalant anesthetic requirements. When using lidocaine, always calculate the maximum safe dose for the species and patient size, and consider the addition of epinephrine to prolong local anesthesia, but avoid in areas with end-arterial supply. For systemic use, administer slowly IV and monitor for CNS and cardiovascular effects. In cats, use lower doses due to increased sensitivity. In food animals, adhere to withdrawal times. Always have emergency drugs (e.g., diazepam, atropine, epinephrine) and equipment available when administering lidocaine systemically.

References & Literature

  • πŸ“š Plumb's Veterinary Drug Handbook
  • πŸ“š Papich Veterinary Pharmacology and Therapeutics
  • πŸ“š Compendium of Veterinary Products (CVP)