This tool is provided for education and reference only. It applies conventional maximum doses to the values you enter. It has no knowledge of your patient.
Published maximum doses are consensus ceilings, not validated safety thresholds. Systemic toxicity has occurred below them and has been avoided above them. The true risk depends on the injection site's vascularity, the rate and technique of injection, protein binding, hepatic and cardiac function, age, and pregnancy — none of which this tool knows.
When agents are combined, this tool assumes their toxicities are additive and sums each drug's percentage of its own ceiling. This is the conventional teaching. There is no validated model for mixtures of local anesthetics, and the assumption may be wrong in either direction.
Output from this tool is not a dosing recommendation and not medical advice. Verify every number independently against the package insert and your institution's guidance. Responsibility for patient care decisions rests entirely with the treating licensed clinician.
Cumulative dose across one or more local anesthetics. Each agent is expressed as a percentage of its own ceiling, and the percentages are summed.
Pick the agent you would actually draw up. Add a second or third to split the remaining budget between them — the share column decides how much of what is left goes to each.
Each agent's dose in milligrams is divided by that agent's own maximum, giving a percentage. The percentages are then added. Lidocaine at half its maximum plus bupivacaine at half of its own maximum totals 100% — at the ceiling, even though neither drug alone is near it.
This is the standard teaching, and it is what most institutional guidance assumes. It is also, strictly, an assumption: there is no validated pharmacokinetic model for mixtures of local anesthetics in humans. Treat the total as a prompt to think, not as a boundary that is safe right up until it is crossed.
Each agent's ceiling is the lower of its weight-based limit and its absolute cap. A 100 kg patient does not get 700 mg of lidocaine with epinephrine, because the absolute cap of 500 mg binds first.
Whatever percentage is left below 100% is the remaining budget. It has no milligram value on its own, because the same percentage is worth a different dose in every agent: 40% left is 70 mg of bupivacaine but 200 mg of lidocaine with epinephrine, in the same patient. The remainder is therefore only meaningful once you say which agent you intend to give, which is what the calculator asks for.
Combining agents divides that remaining budget between them. Giving half of it as bupivacaine and half as ropivacaine means half of bupivacaine's remaining allowance and half of ropivacaine's — not half the milligrams of each, since the two ceilings differ.
| Agent | Plain mg/kg |
With epi mg/kg |
Cap plain mg |
Cap epi mg |
|---|
Conventional values. Published maxima differ between textbooks, package inserts, and national guidance — in some cases substantially. Epinephrine does not meaningfully raise the ceiling for ropivacaine or levobupivacaine, both of which are intrinsically vasoconstrictive at clinical concentrations, so those rows are unchanged.