Local anesthetics (lidocaine / bupivacaine ± mepivacaine)

What is this medication for?

• Local/regional anesthesia: infiltration, line/incisional blocks, nerve blocks (dental), epidurals; topical (EMLA for venipuncture/catheter placement); into a vein lidocaine CRI for perioperative/hyperalgesic analgesia; lidocaine systemic = ventricular antiarrhythmic (see pearls)

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Methemoglobinemia (prilocaine/EMLA large-surface use) (Class effect)
• Cat CNS/cardiodepressant sensitivity (into a vein lidocaine) (Species caution — controversial as antiarrhythmic)

Worth a phone call to your veterinarian

• Any new symptom that worries you.

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Systemic toxicity (intravascular injection/overdose): CNS excitation → seizures (lidocaine-type) vs CARDIAC collapse/arrest (bupivacaine-type) (The feared complication — calculate max dose BEFORE drawing up)
• Epidural: respiratory paralysis with high doses (Technique-dependent)

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Amide hypersensitivity; severe SA/AV/intraventricular block (unpaced), Adams-Stokes (systemic use)
• has or has had: Hepatic disease/CHF/shock/hypovolemia (systemic absorption + clearance); bupivacaine never into a vein for regional purpose; malignant-overheating-susceptible monitoring

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Other antiarrhythmics, beta-blockers, CCBs
  • Cimetidine/beta-blockers (human)
  • Opioids/α2 (deliberate)
  • into a vein lipid emulsion

Storage and handling

Preservative-free for epidural/spinal; multidose with preservative for infiltration only; EMLA topical.

Good to know

• Draw the dose map first: know the animal's max mg (e.g., cat bupivacaine <2 mg/kg, toxic at 5) before the syringe is filled — "a little more for good effect" is how LA deaths happen.
• Lidocaine = fast/short/safe-ish (CNS warns first); bupivacaine = slow/long/cardiotoxic (no warning, arrest) — which drug for a dental nerve block vs a line block follows directly.
• Lipid rescue (IVFE): intralipid is the antidote for systemic local-anesthetic toxicity — bupivacaine's lipophilicity is literally its Achilles heel.
• into a vein lidocaine's triple life: local anesthetic → ventricular antiarrhythmic → perioperative analgesic/anti-hyperalgesic CRI (cats: caution at every turn).