Lidocaine (Lignocaine)
Lidocaine provides local anaesthesia and treats selected ventricular arrhythmias; IV infusions are also used for analgesia and equine postoperative ileus.
Group
Local anaesthetic and class Ib antiarrhythmic
Mechanism of Action
Blocks voltage-gated sodium channels, inhibiting nerve conduction and abnormal ventricular depolarization.
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 and epidural anaesthesia
- Ventricular arrhythmias
- Perioperative analgesia
- Equine postoperative ileus
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.