What lidocaine intravenous drip loading dose and maintenance infusion rate should be used in a 70‑kg adult for ventricular arrhythmia suppression or systemic analgesia?

Lidocaine Intravenous Drip Dosing for a 70-kg Adult

For ventricular arrhythmias in a 70-kg adult, administer an initial bolus of 70-100 mg (1-1.5 mg/kg) IV over 2-3 minutes, followed by a maintenance infusion of 1.4-3.5 mg/min (20-50 mcg/kg/min); for systemic analgesia, use a loading dose of 1-3 mg/kg over 20-30 minutes followed by continuous infusion of 0.5-2 mg/kg/hr (maximum 100 mg/hour). 1

Ventricular Arrhythmia Suppression

Loading Dose Protocol

• Initial bolus: 1 mg/kg (70 mg for a 70-kg patient), not to exceed 100 mg, given as IV bolus 1
• Additional boluses: 0.5 mg/kg (35 mg) can be repeated every 8-10 minutes if needed, up to a total cumulative dose of 4 mg/kg (280 mg) 1
• Patients requiring multiple boluses to suppress arrhythmias will likely need higher maintenance infusion rates (up to 40-50 mcg/kg/min) 1

Maintenance Infusion

• Standard rate: 20-50 mcg/kg/min, which equals 1.4-3.5 mg/min in a 70-kg patient 1
• This produces therapeutic blood levels up to 5 mcg/mL 1
• Critical adjustment: A second bolus of 0.5 mg/kg may be needed at 30-120 minutes after initiation to maintain therapeutic levels, as transient subtherapeutic concentrations commonly occur during this window 1

Duration and Dose Reduction

• Reduce infusion rate by 1 mg/min at 12 hours (preferably) or by 24 hours at the latest, as lidocaine half-life increases from 1-2 hours initially to >4 hours after 24-48 hours of infusion 1
• In patients with heart failure, the half-life extends to >20 hours; in cardiogenic shock, even longer—requiring substantial dose reductions 1

Special Cardiac Arrest Situations

• In cardiac arrest with ventricular fibrillation: use 100 mg bolus initially, repeated every 2-3 minutes as needed 1
• Only bolus therapy should be used during active cardiac arrest (no infusions) 1
• Lidocaine remains the first-line antiarrhythmic for persistent VT/VF despite defibrillation and epinephrine 1

Important caveat: While lidocaine reduces ventricular arrhythmia incidence, it does not reduce overall mortality in acute MI and may increase risk of asystole 1. Modern evidence shows amiodarone is more effective than lidocaine for shock-resistant VT (78% vs 27% immediate termination rate, p<0.05) 2.

Systemic Analgesia (Cancer Pain/Refractory Pain)

Loading Dose

• 1-3 mg/kg over 20-30 minutes (70-210 mg for a 70-kg patient) 1
• If this bolus is tolerated and effective at reducing pain, proceed to continuous infusion 1

Maintenance Infusion

• 0.5-2 mg/kg/hr using the lowest dose that controls pain 1
• Maximum rate: 100 mg/hour regardless of weight 1, 3
• For a 70-kg patient, this translates to approximately 35-140 mg/hour, but never exceed 100 mg/hour 1, 3

Duration Limits for Analgesia

• Maximum initial duration: 24 hours for most postoperative pain patients 4
• If extending beyond 24 hours: Reduce infusion rate to 50% of original rate due to time-dependent pharmacokinetics (half-life increases from 100 minutes to 3.22 hours after 24 hours) 3, 4
• Extension beyond 24 hours requires consultant anesthesiologist or intensivist approval 4

Evidence for Analgesic Use

• Lidocaine may be particularly effective for opioid-refractory cancer pain and neuropathic pain 1
• One randomized trial showed 38% of patients achieved ≥20% pain reduction with continuous infusion 5
• Side effects (tinnitus, perioral numbness, sedation, lightheadedness) are typically self-limiting 1

Critical Safety Considerations

Dosing Calculations

• Use ideal body weight, not actual body weight, especially in obese patients (BMI >30 kg/m²) 3
• Do not use IV lidocaine in patients <40 kg 3

Monitoring Requirements

• Continuous ECG monitoring, pulse oximetry, and regular blood pressure measurements 3
• Monitor every 15 minutes for first hour, then hourly minimum 4
• 20% lipid emulsion must be immediately available wherever IV lidocaine is used 3, 4

Toxicity Recognition

• Early signs (5-10 mcg/mL): Circumoral numbness, facial tingling, tinnitus, lightheadedness, slurred speech 1, 3
• Severe toxicity (>10 mcg/mL): Muscle twitching, seizures, loss of consciousness, respiratory arrest, cardiac arrhythmias 1, 3
• Discontinue immediately if any toxicity signs appear 1

Drug Interactions and Contraindications

• Do not administer within 4 hours of other local anesthetic interventions to prevent cumulative toxicity 3
• Beta-blockers and amiodarone reduce lidocaine metabolism, increasing toxicity risk 3
• Contraindicated in advanced liver failure due to decreased clearance 3

High-Risk Populations Requiring Dose Reduction

• Age >70 years 1
• Heart failure (half-life >20 hours) 1
• Cardiogenic shock (half-life even more prolonged) 1
• Hepatic dysfunction 3
• Hypoalbuminemia (increases free drug concentration) 3

Common pitfall: Failing to give the second bolus at 30-120 minutes after initial loading leads to subtherapeutic levels and arrhythmia recurrence 1. Similarly, failing to reduce the infusion rate after 12-24 hours risks accumulation and toxicity 1, 3.