Generic Name

Bupivacaine

Mechanism

• Nav channel blockade: Bupivacaine preferentially binds to the closed‑state of voltage‑gated sodium channels (Nav1.7–1.9) in neuronal membranes, stabilizing the inactivated state and preventing depolarization.
• High affinity for nerve fibres: Subcutaneous or end‑pial injection yields intense, long‑lasting sensory and motor block.
• Protein binding & lipid solubility: 95 % bound to plasma proteins and readily diffuses through lipid‑rich nerve membranes, resulting in rapid onset (~1–5 min) and duration of 2–8 h (peripheral), up to 12–16 h (epidural).

Pharmacokinetics

Indications

• Peripheral nerve blocks for infra‑umbilical surgery or postoperative analgesia.
• Epidural or spinal anaesthesia for cesarean section, abdominal, or lower‑limb procedures.
• Intra‑articular infiltrations (knee arthroscopy, hip arthroscopy).
• Topical or local infiltration in dental or minor skin procedures (stable‑dose preservatives used).

Contraindications

• Absolute contraindications:
• Known hypersensitivity to amide local anaesthetics.
• Severe cardiac conduction disease (e.g., second‑degree AV block).
• Pre‑existing hepatic failure (CYP3A4 deficiency).
• Relative contraindications:
• Pregnancy (placental transfer).
• Neurological disorders (seizure, neuro‑toxicity risk).
• Warnings:
• Systemic toxicity (CNS: tinnitus, metallic taste, seizures; cardiac: arrhythmias, hypotension).
• Accidental intravascular injection—requires immediate CPR and lipid emulsion therapy.

Dosing

• Peripheral nerve block: 0.25 % to 0.5 % solution, 0.4–0.5 mL/kg (max 5–6 mL for single block).
• Epidural: 0.25 % to 0.5 % solution, 10–15 mL for dense block, titrate with epidural catheter.
• Spinal: 0.5 % solution, 2.5–3.0 mg for cauda equina block; lower dose (1–2 mg) for low‑dose epidural anesthesia.
• Topical: 0.25–0.5 % solution for ketamine‑free anesthesia, 50–100 µg/kg IV for multimodal analgesia.
• Maximum daily dose: 4 mg/kg; lower dose (<2 mg/kg) for children or elderly.

Adverse Effects

Common
• Somnolence, dizziness, tinnitus
• Positive sensory block without motor impairment (rare)

Serious
• CNS toxicity: agitation, seizures, respiratory arrest
• Cardiac toxicity: bradycardia, ventricular fibrillation, hypotension
• Allergic reactions: urticaria, angioedema, anaphylaxis
• Musculoskeletal: local nerve injury, prolonged muscle weakness (rare)

Monitoring

• Vitals: continuous BP, HR, SpO₂, ECG (especially if high dose or neuraxial).
• Neurologic: onset of analgesia, signs of early toxicity (tinnitus, metallic taste).
• Pain score: assess block adequacy.
• RER: monitor for respiratory depression if combined systemic sedation.
• Laboratory: electrolytes, plasma bupivacaine level in suspected toxicity (limit not widely available).

Clinical Pearls

• “Hypo‑osmia” as a toxicity cue: loss of smell is one of the earliest subtle signs of systemic bupivacaine toxicity. Use it as a bedside sentinel.
• Epidural “maximal safe dose”: Keep single‑bolus dose ≤5 mg for patients >60 y or with liver dysfunction; lower for pregnant patients.
• Additive CNS depression: Avoid mixing bupivacaine with ketamine or benzodiazepines; monitor closely.
• Lipid emulsion first‑line: At the first sign of systemic toxicity, administer 20 % lipid emulsion 1.5 mL/kg IV over 1 min, then repeat if no response.
• Topical safety: When using topical 0.25 % bupivacaine, never exceed 200 µg/kg total dose; adjust for obese or pediatric patients.
• Pregnancy: It crosses the placenta; use the lowest effective dose and monitor fetal heart tones.
• Non‑neuraxial use in obese patients: Higher weight may necessitate dose adjustment; however, plasma protein binding remains consistent, making safety hinge on total systemic exposure.

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• References: UpToDate, Lexicomp, WHO Model List of Essential Medicines.