Refresher: Why use local anesthetics?

This summary is based on the Clinical Info provided by the Canadian Pharmacists Association: Drugs in Dentistry (December 2012)

By Dr. Dan Haas, DDS, PhD, FRCDC

Potential Interactions with Epinephrine or Levonordefrin: Adding epinephrine or levonordefrin to the local anesthetic formulation improves the depth and duration of the local anesthetic block. However, exercise caution if a patient has a history of significant cardiovascular disease or is concomitantly taking any of the following drugs:

• Nonselective beta-blockers such as nadolol, pindolol, propranolol, sotalol or timolol (may result in increased blood pressure).
• Tricyclic antidepressants (may result in increased blood pressure and cardiac dysrhythmias).

In these cases, use the lowest effective dose of epinephrine and consider a maximum of <40 µg. The administration of levonordefrin is contraindicated in individuals taking tricyclic antidepressants. For those with cardiovascular disease or taking nonselective beta-blockers, use the lowest effective dose of levonordefrin and consider a maximum of<200 µg.

• Avoid epinephrine altogether in patients who have ingested cocaine within the previous 24 hours, as there is increased risk of cardiac dysrhythmias and increased blood pressure. 
• The dose of vasoconstrictor delivered per 1.8 mL dental cartridge is as follows: 

• 1 cartridge of 1:200 000 epinephrine = 9 µg 
• 1 cartridge of 1:100 000 epinephrine = 18 µg 
• 1 cartridge of 1:50 000 epinephrine = 36 µg 
• 1 cartridge of 1:20 000 levonordefrin = 90 µg. 

Maximum Recommended Doses of Local Anesthetics

Expected Duration of Action (minutes) of Local Anesthetics

References

1. Haas DA. Adverse drug interactions in dental practice: interactions associated with analgesics, Part III in a series. J Am Dent Assoc 1999;130(3):397-407.
2. Haas DA. An update on analgesics for the management of acute postoperative dental pain. J Can Dent Assoc 2002;68(8):476-82. 

3. Yagiela JA. Adverse drug interactions in dental practice: interactions associated with vasoconstrictors. Part V of a series. J Am Dent Assoc 1999;130(5):701-9.

4.  Malamed SF. Handbook of local anesthesia. 6th ed. St. Louis (MO): Mosby; 2013.

5.  Jastak JT, Yagiela JA, Donaldson D, editors. Local anesthesia of the oral cavity. Philadelphia (PA): Saunders; 1995.

6.  Yagiela JA, Dowd FJ, Johnson BS, editors. Pharmacology and therapeutics for dentistry. 6th ed. St. Louis (MO): Mosby/Elsevier; 2011.

7. Haas DA. An update on local anesthetics in dentistry. J Can Dent Assoc 2002;68(9):546-51.

8.  Yagiela J. Local anesthetics. In: Dionne RA, Phero JC, Becker DE, editors. Management of pain & anxiety in the dental office. Philadelphia (PA): Saunders; 2002. p. 78-96.

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