Local Anesthetic Maximum Safe Dose Calculator (Lidocaine & Bupivacaine)
Calculate the maximum safe total dose and volume of lidocaine or bupivacaine before performing a dental nerve block or other regional block in dogs and cats.
Drug
Species
Patient weight (kg)
Solution concentration
2% = 20 mg/mL
Conservative ceiling used: 4 mg/kg for lidocaine in dogs (up to 6 mg/kg is cited in some references, but this calculator flags against the lower, more conservative figure).
Total dose, not per-site dose.
These are literature-cited conservative ceilings for TOTAL dose across all injection sites in one anesthetic event - not a per-site dose. Always use the lowest effective volume for the specific block being performed, account for any local anesthetic already given elsewhere in the same patient, and consult your anesthesia reference for the specific technique. Signs of local anesthetic systemic toxicity include tremors, seizures, and cardiac arrhythmia/arrest - bupivacaine cardiotoxicity in particular can be resistant to standard resuscitation.
How to use this tool
Conservative ceilings used
Lidocaine: 4 mg/kg in dogs (up to 6 mg/kg cited in some references), 2 mg/kg in cats (up to 4 mg/kg cited). Bupivacaine: 1 mg/kg in dogs (up to 2 mg/kg cited), 1 mg/kg in cats. Cats are more sensitive to local anesthetic systemic toxicity, particularly bupivacaine cardiotoxicity, so the calculator leans conservative for cats.
The math
Max total dose (mg) = conservative mg/kg ceiling × body weight (kg). Max volume (mL) = max total dose (mg) ÷ concentration in mg/mL, where concentration % × 10 = mg/mL (e.g. 2% = 20 mg/mL).
Total dose, not per site
This is the ceiling across ALL injection sites in one anesthetic event. If you need more volume than the ceiling allows to cover the area, dilute the solution with sterile saline rather than exceeding the total mg limit. Track cumulative dose across every block performed in the same patient.
Frequently asked questions
Why is the max dose ceiling lower for cats than dogs?
Cats are generally more sensitive to local anesthetic systemic toxicity, particularly the cardiotoxic effects of bupivacaine, so conservative references use lower mg/kg ceilings for cats than dogs.
What do you do if the calculated max volume isn't enough to cover the area you need to block?
Dilute the local anesthetic solution with sterile saline - this increases the volume you can use to cover a larger area while keeping the total mg dose under the same safety ceiling, rather than exceeding the max total dose.
What are the signs of local anesthetic toxicity?
Early signs can include muscle tremors and behavioral changes, progressing to seizures; bupivacaine in particular carries a risk of severe, resuscitation-resistant cardiac arrhythmia and arrest if the toxic threshold is exceeded - it should never be given intravenously.
Does this calculator account for multiple blocks in the same patient?
No - this calculates the total safe ceiling for ONE anesthetic event. If you're performing multiple blocks (e.g. several dental nerve blocks), you must track the CUMULATIVE volume/dose given across all sites against this same total ceiling, not treat each site as a fresh allowance.