Lidocaine (Lignocaine)

Lidocaine, also called lignocaine, is an amide local anesthetic with additional class Ib antiarrhythmic activity. It is used for local and regional nerve blockade and for selected ventricular arrhythmias. Intravenous infusions also have adjunctive analgesic applications, particularly in dogs and horses, and a specialist role in management of equine postoperative ileus.

Group

Local anaesthetic and class Ib antiarrhythmic

Mechanism of Action

Lidocaine blocks voltage-gated sodium channels, particularly when they are open or inactivated. In peripheral nerves, this interrupts action-potential propagation and produces local anesthesia. In ventricular tissue, it suppresses abnormal automaticity and excitability, supporting antiarrhythmic action. Systemic analgesic effects include modulation of nociceptive signaling; proposed effects in equine ileus also involve inflammatory and pain pathways, with the full mechanism unresolved.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Ventricular arrhythmia bolus	2–4 mg/kg	IV		Cumulative maximum 8 mg/kg over 10 minutes. Track the cumulative amount delivered within that 10-minute window.
Ventricular arrhythmia infusion — Loading	1 mg/kg	IV
Ventricular arrhythmia infusion — Maintenance	50–75 mcg/kg/min	IV	Continuous
Ventricular arrhythmia	6 mg/kg	IM	Every 1.5 h
Epidural anaesthesia	4.4 mg/kg	EPIDURAL	Once	Use an appropriate 2% preservative-free solution.
Perioperative analgesia — Loading	2 mg/kg	IV
Perioperative analgesia — Maintenance	0.05 mg/kg/min	IV	Continuous	Up to 1 days
Ventricular arrhythmia infusion — Maintenance	40–80 mcg/kg/min	IV	Continuous	Separate titration alternative, with ECG monitoring.
Ventricular arrhythmia infusion — Maintenance	25–80 mcg/kg/min	IV	Continuous	Separate titration alternative, with ECG monitoring.
Ventricular arrhythmia infusion — Maintenance	25–75 mcg/kg/min	IV	Continuous	Separate titration alternative, with ECG monitoring.
Ventricular arrhythmia	4 mg/kg	IM		Do not use the IM alternative in shock; onset approximately 10-15 minutes.
Analgesic infusion	2–4 mg/kg/hour	IV	Continuous
Analgesic infusion — Loading	1–4 mg/kg	IV
Analgesic infusion — Maintenance	1–5 mg/kg/hour	IV	Continuous
Alternative perioperative analgesia — Loading	2 mg/kg	IV		Give over 2-3 minutes.
Alternative perioperative analgesia — Maintenance	50–100 mcg/kg/min	IV	Continuous
Epidural anaesthesia	4–5 mg/kg	EPIDURAL	Once	Appropriate preservative-free formulation; effects start within about 10 minutes and last around 1.5 hours.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Epidural anaesthesia	4.4 mg/kg	EPIDURAL	Once	Use an appropriate 2% preservative-free solution.
Ventricular arrhythmia bolus — Initial	0.1–0.4 mg/kg	IV		Administer slowly and reassess cardiovascular response.
Ventricular arrhythmia bolus — Maintenance	0.25–0.75 mg/kg	IV		Subsequent escalation only if there has been no response to the initial dose.
Ventricular arrhythmia infusion — Loading	0.5–1 mg/kg	IV
Ventricular arrhythmia infusion — Maintenance	10–20 mcg/kg/min	IV	Continuous	Equivalent to 0.6-1.2 mg/kg/hour; cats have increased cardiotoxicity risk.
Epidural anaesthesia	4–5 mg/kg	EPIDURAL	Once	Appropriate preservative-free formulation; effects start within about 10 minutes and last around 1.5 hours.
Ventricular arrhythmia bolus — Initial	0.25–0.5 mg/kg	IV		Slow IV; subsequent 0.15-0.25 mg/kg in 5-20 minutes only according to response. Track cumulative exposure.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Ventricular tachycardia — Initial	0.25–0.5 mg/kg	IV		Administer over 5-10 minutes; refractory cases have received 1.3-1.5 mg/kg.
Ventricular tachycardia — Maintenance	30–50 mcg/kg/min	IV	Continuous
Postoperative ileus — Loading	1.3 mg/kg	IV		Administer over 15 minutes.
Postoperative ileus — Maintenance	50 mcg/kg/min	IV	Continuous
Analgesia — Loading	2 mg/kg	IV
Analgesia — Maintenance	50 mcg/kg/min	IV	Continuous
Ventricular tachycardia — Initial	1–1.5 mg/kg	IV		Monitor ECG and follow with an individualized infusion if effective.
Colic-associated ileus or pain — Loading	1.4 mg/kg	IV
Colic-associated ileus or pain — Maintenance	0.03–0.05 mg/kg/min	IV	Continuous

Indications

Local infiltration, topical mucosal anesthesia and regional nerve blockade for veterinary procedures.
Epidural or other regional anesthesia with an appropriate formulation and technique.
Treatment of selected ventricular tachyarrhythmias, particularly ventricular tachycardia or clinically significant ventricular premature complexes.
Adjunctive perioperative or trauma-associated analgesia using a systemic infusion in selected patients.
Specialist management of postoperative ileus in horses.

Contraindications

Cats are especially susceptible to systemic cardiotoxicity.
Reduced hepatic blood flow can decrease clearance.
Avoid epinephrine-containing formulations for antiarrhythmic use.
Major SA/AV/intraventricular block without pacing, or amide-local-anaesthetic hypersensitivity.

Interactions

Alkaline storage mixtures can precipitate lidocaine hydrochloride; administer promptly if buffering is used.

Adverse effects

Tremors, seizures, fasciculations, ataxia and vomiting
Cardiovascular depression and arrhythmias
Feline methaemoglobinaemia and haemolysis

Toxicity

Stop administration and support airway, ventilation and circulation; manage seizures and consider lipid-emulsion treatment for severe systemic local-anaesthetic toxicity.

Preparations

Preparation	Form	Strength	Route
Lidocaine (Lignocaine) 5 mg/mL injection Plain lidocaine, without epinephrine; strength stated for the hydrochloride preparation.	Injection	5 mg / mL	IV, IM
Lidocaine (Lignocaine) 10 mg/mL injection Plain lidocaine, without epinephrine; strength stated for the hydrochloride preparation.	Injection	10 mg / mL	IV, IM
Lidocaine (Lignocaine) 15 mg/mL injection Plain lidocaine, without epinephrine; strength stated for the hydrochloride preparation.	Injection	15 mg / mL	IV, IM
Lidocaine (Lignocaine) 20 mg/mL injection Plain lidocaine, without epinephrine; strength stated for the hydrochloride preparation.	Injection	20 mg / mL	IV, IM
Lidocaine 20 mg/mL preservative-free epidural solution Preservative-free formulation only; no epinephrine.	Injection	20 mg / mL	EPIDURAL

Monitoring and Administration

Use continuous ECG for antiarrhythmic treatment and observe for neurologic toxicity, especially in cats.

For the described buffering method, 1 mEq sodium bicarbonate is added to 10 mL lidocaine and used immediately. Avoid prolonged storage of buffered mixtures.

Epidural use requires an appropriate preservative-free formulation.

Published guidance describes equine lidocaine 10 g added to 3 L LRS as approximately 0.33%; actual final volume must be established before a mixing calculation.

For refractory equine ventricular arrhythmias, magnesium sulfate may be added as a separate assessed treatment: published guidance describes 2.7 g in 1 L saline over 10 minutes, corresponding to approximately 2-6 mg/kg in its patient context. Do not mix magnesium into calcium-containing fluid.

The morphine-lidocaine-ketamine combination targets morphine 0.24, lidocaine 3 and ketamine 0.6 mg/kg/hour. The recipe amounts do not produce all target rates at a single common fluid rate; a validated combination recipe is required.

Topical lidocaine/EMLA may be applied as a thin layer every 3-4 hours as needed. Avoid eyes and unlabelled ear use, large areas and prolonged exposure; prilocaine increases methaemoglobinaemia risk. Wash hands or wear gloves. Topical concentration ranges alone do not establish an exact mass per mL or gram for every product.