Bupivacaine
Bupivacaine is a potent, long-acting amide local anaesthetic used widely in veterinary medicine for regional, epidural, and perineural analgesia. It is characterized by a relatively slow onset of action compared to lidocaine but provides a significantly prolonged duration of effect (6-8 hours). > **WARNING:** Bupivacaine is highly cardiotoxic if administered intravenously. Extreme care must be taken to aspirate before injection to ensure the needle is not in a blood vessel. **Clinical Pearl:** Small volumes of bupivacaine can be diluted with normal saline to enable wider distribution of the drug for perineural blockade. It can also be combined with lidocaine to provide both a rapid onset (from lidocaine) and prolonged duration (from bupivacaine) of sensory block while limiting the duration of motor blockade.
Mechanism: Bupivacaine produces reversible blockade of **voltage-gated sodium channels** in nerve fibres → prevents the influx of sodium required for depolarization → inhibits the propagation of action potentials → results in local anaesthesia and analgesia.
Dosing by species
- Regional, epidural, perineural, or intrapleural analgesia · Up to 2 mg/kg · Perineural/Epidural/Intrapleural · q8h · As needed · Unlikely to be associated with systemic side effects at this dose. Onset is 20-30 minutes for epidural; duration is 6-8 hours.
- Regional, epidural, perineural, or intrapleural analgesia · Up to 2 mg/kg · Perineural/Epidural/Intrapleural · q8h · As needed · Unlikely to be associated with systemic side effects at this dose. Cats may be more sensitive to local anaesthetic toxicity; use conservative dosing.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Intravenous (IV) administration
- Intravenous regional anaesthesia (Bier block)
- Use of adrenaline-containing formulations at end-arterial sites (e.g., tail, digits, ears)
- Use of adrenaline-containing formulations when significant systemic absorption is likely
Adverse effects
- Severe cardiac arrhythmias (if injected intravascularly)
- Motor blockade (paresis/paralysis of affected limbs)
- CNS toxicity (seizures, tremors) at high systemic doses
- Hypotension (especially with epidural use)
Drug interactions
- Other local anaesthetics (e.g., lidocaine, mepivacaine) · Additive systemic toxicity; doses must be reduced when used concurrently. · major
Monitoring
- Aspiration for blood prior to injection (mandatory)
- Electrocardiogram (ECG) during and after block placement
- Blood pressure
- Respiratory rate and effort (especially with epidural or intrapleural use)
- Motor function recovery
Overdose
Overdose or inadvertent IV injection leads to profound **CNS toxicity** (muscle twitching, seizures, coma) and **cardiovascular toxicity** (profound hypotension, bradycardia, ventricular arrhythmias, asystole). > **Clinical Pearl:** Bupivacaine-induced cardiac arrest is notoriously resistant to standard CPR. **Intravenous Lipid Emulsion (ILE) therapy** (e.g., Intralipid 20%) is the specific antidote and should be administered immediately alongside standard resuscitation efforts.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.