Local Anesthetic Calculator
Calculate maximum subcutaneous doses for bupivacaine, lidocaine, mepivacaine, and ropivacaine by weight.
Maximum Local Anesthetic Doses
Amide-type local anesthetics without epinephrine have weight-based maximum subcutaneous doses to limit systemic toxicity. This calculator determines the maximum allowable dose in milligrams and the corresponding volume at a chosen concentration for bupivacaine, lidocaine, mepivacaine, and ropivacaine. Always verify dosing against current product labeling and institutional protocols before administration.
How Doses Are Calculated
Maximum dose in mg equals the lesser of (mg/kg × patient weight in kg) and the drug-specific absolute maximum. Maximum volume in mL equals mg/kg × (weight kg ÷ 10) × (1 ÷ concentration percent). For example, lidocaine allows 4.5 mg/kg up to 300 mg; a 60 kg patient receives 270 mg, which at 1% concentration corresponds to 27 mL.
Drug-Specific Limits
Bupivacaine: 2 mg/kg, not to exceed 175 mg. Lidocaine: 4.5 mg/kg, max 300 mg. Mepivacaine: 4.4 mg/kg, max 400 mg. Ropivacaine: 3 mg/kg, max 225 mg. Bupivacaine carries a prominent safety warning because its long duration and high potency increase the risk of cardiac toxicity when limits are exceeded.
Frequently Asked Questions
Why is there a separate bupivacaine warning at 175 mg?
Bupivacaine has high cardiotoxic potential. Even when the weight-based calculation exceeds 175 mg, a single subcutaneous dose without epinephrine should not exceed 175 mg. The calculator caps the dose and displays a warning when this limit applies.
Does this calculator include epinephrine-containing solutions?
No. These maximum doses apply to subcutaneous administration of amide local anesthetics without epinephrine. Epinephrine allows higher total doses by slowing systemic absorption; use epinephrine-specific limits when applicable.
How do I convert concentration percent to mg/mL?
A 1% solution contains 10 mg/mL (each 1% equals 10 mg per mL). A 0.5% solution contains 5 mg/mL, and a 2% solution contains 20 mg/mL. The volume formula accounts for concentration directly as a percentage.
Which anesthetic has the longest duration of action?
Bupivacaine and ropivacaine generally provide longer anesthesia than lidocaine and mepivacaine due to greater protein binding. Duration also depends on site, vascularity, and whether epinephrine is added.
Can I use this for nerve blocks or infiltration?
Maximum dose limits vary by route, site, and patient factors. This tool estimates subcutaneous maximums without epinephrine. Consult anesthesia references and verify institutional policies before regional or major nerve block procedures.
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