Precautions

Adverse Effects

Adverse reactions to Lidocaine are rare and usually the result of intravascular injection, excessive dosage or rapid absorption from highly vascular areas.

• Systemic Signs: Toxicity mainly involves the

• Central Nervous System: Drowsiness, ataxia, muscle tremors, depression,  and seizures have been reported.

• Cardiovascular: Decreased cardiac output, cardiovascular depression, and decreased oxygen delivery to tissues have been reported. PR and QRS interval prolongation and QT interval shortening have also been reported. Lidocaine can produce cardiac arrhythmias but has a more significant effect on abnormal than normal cardiac tissue (Papich, 2011; SPC Data).

• Haemolysis and Methemoglobinemia:  Methemoglobinemia and hemolysis have been reported in humans and cats (Katsuki et al., 2004; Khajavirad et al., 2023; Papich, 2011)

• Epidural Administration:  Use may result in hypotension, urinary retention, and/or ataxia (SPC Data).

• Epinephrine Formulations: Systemic absorption or IV injection may cause tachycardia and hypertension (Papich, 2011; SPC Data).

Contraindications

The following contraindications relate to using preparations containing adrenaline ( epinephrine). 

• Cardiovascular Disease: Avoid lidocaine/epinephrine formulations in patients with cardiovascular disease.

• Extremities: Lidocaine/epinephrine formulations should not be used in extremities (e.g. digits, ears, nose, or penis) as ischemic injury may result.

• Intravenous Use: Lidocaine/epinephrine formulations should not be used intravenously.

Reproductive Safety

• Pregnancy: Avoid Use; lidocaine should not be administered during early pregnancy unless the benefits are considered to outweigh the risks. Lidocaine crosses the placental barrier after epidural or intravenous administration but recommended dose levels are unlikely to have adverse effects (Demeulemeester et al., 2018; Hagai et al., 2015; Morishima et al., 1990; Ramanathan et al., 1986; Reynolds, 2011; Smith et al., 1986).

• Lactation: Small amounts of Lidocaine are secreted into breast milk, but recommended dose levels are not expected to cause any adverse effects in breastfed infants. No special precautions are required (LactMed, 2006; Reynolds, 2011; Zeisler et al., 1986).

• Male Fertility: No data available (SPC data).

• Female Fertility: No data available (SPC data).

• Neonates: No data available (SPC data).

Significant Interactions

General Information: Significant Interactions are unlikely when lidocaine is administered as recommended.

• Anaesthetic Agents (e.g., isoflurane, sevoflurane): Lidocaine infusions perioperatively reduce MAC requirements

• Antiarrhythmics (e.g., procainamide, propranolol, quinidine): If systemically absorbed, lidocaine may cause additive or antagonistic cardiac effects, and toxicity may be enhanced.

• β-Adrenergic Antagonists (e.g., atenolol, esmolol, propranolol, sotalol): Lidocaine levels or effects may be increased.

• Morphine: Coadministration of morphine and lidocaine has demonstrated a beneficial synergistic interaction during visceral nociception 

Overdose

• Maximum Dose:  We recommend a maximum therapeutic dose of 2 mg/kg per administration for rabbits regardless of route, with a maximum administration of 0.5 mg/kg at any site until clear information regarding toxic doses in rabbits is available.

• Toxic Doses: We regard doses above 4mg/kg as potentially toxic. However, the cumulative convulsive dose and cumulative lethal (cardiotoxic) dose are likely to be far higher (25 mg/kg) (Schnellbacher et al., 2013).

Management

• Oxygen: If signs of overdose are present, management must begin with the delivery of oxygen via a patent airway, as successful oxygen delivery may prevent convulsions caused by toxicity (Barletta and Reed, 2019).

• Vascular Decontamination: Intravenous lipids may be helpful where available. Lipid emulsion 20% 1.5 mL/kg IV over 30 minutes can benefit veterinary lidocaine toxicity (Markert et al., 2023).