How is concentration and dilution measured in local anesthetic toxicity?

Updated: Jan 09, 2019
  • Author: Raffi Kapitanyan, MD; Chief Editor: David Vearrier, MD, MPH  more...
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Answer

Drug concentration is expressed as a percentage (eg, bupivacaine 0.25%, lidocaine 1%). Percentage is measured in grams per 100 mL (ie, 1% is 1 g/100 mL [1000 mg/100 mL], or 10 mg per mL).

Calculate the mg/mL concentration quickly from the percentage by moving the decimal point 1 place to the right, as in the following examples:

  • Bupivacaine 0.25% = 2.5 mg/mL

  • Lidocaine 1% = 10 mg/mL

When epinephrine is combined in an anesthetic solution, the result is expressed as a dilution (eg, 1:100,000), as follows:

  • 1:1000 means 1 mg per 1 mL (ie, 0.1%)

  • 1:10,000 means 1 mg per 10 mL (ie, 0.01%)

  • 1:2000 means 1 mg per 2 mL (ie, 0.05%)

  • 1:20,000 means 1 mg per 20 mL (ie, 0.005%)

  • 0.1 mL of 1:1000 epinephrine added to 9.9 mL of anesthetic solution = 1:100,000 dilution or 0.01 mg/mL

For higher dilutions, see Table 1, below.

Table 1. Epinephrine Content Examples (Open Table in a new window)

Solution Volume

1:100,000 (1 mg/100 mL)

1:200,000 (1 mg/200 mL)

1 mL

0.01 mg

0.005 mg

5 mL

0.05 mg

0.025 mg

10 mL

0.1 mg

0.05 mg

20 mL

0.2 mg

0.1 mg

Example: 50 mL of 1% lidocaine with epinephrine 1:100,000 contains lidocaine 500 mg and epinephrine 0.5 mg.


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