Update on Maximum Recommended Dosages for Local Anesthesia

The United States Food and Drug Administration(FDA) Center for Drug Evaluation and Research, Office of Pharmaceutical Science, Informatics and Computational Safety Analysis created and consistently updates maximum recommended dosages (MRDs) for local anesthetic drugs, although some clinicians may not know they exist.¹ Many oral health professionals use the MRDs published in the most popular textbooks on local anesthesia when calculating drug dosages for patients, which may differ significantly from the values used in the FDA-approved recommendations (Table 1).

Oral health professionals—particularly those in the Western US—have been guided for a number of years by lower MRD values than those approved by the FDA.^2–4 There are benefits to following lower MRDs, such as enhancing patient safety. As long as the values administered are within the FDA recommendations, there is no breach of these guidelines. However, maintaining two different sets of guidelines can be confusing for the dental team, as Stanley F. Malamed, DDS, a leading expert in local anesthesia, noted in the July issue of Dimensions of Dental Hygiene.⁵

Removing the possibility of this confusion provides a strong rationale for eliminating the non FDA established values.⁵ At this time, not everyone has adopted the higher values; for example, the American Academy of Pediatric Dentistry (AAPD) continues to list the lower values in its monograph (Table 2).^5,6 Like the AAPD, other organizations, individual clinicians, and clinics that use the lower MRDs provide an additional layer of safety to their protocols without compromising treatment or comfort.

IN PRACTICE

The impact of the differences in the recommendations can be illustrated using the following example with 2% lidocaine, 1:100,000 epinephrine. The lower values for lidocaine are 2 mg/lb maximum, with an absolute maximum of 300 mg per appointment. ³ When calculating the MRD using these lower values, a healthy 150-lb individual may receive eight cartridges of 2% lidocaine, 1:100,000 epinephrine, rounded down to the nearest half cartridge.^3,4 The established FDA recommendations are 3.2 mg/lb with an absolute maximum of 500 mg per appointment.² When using these values, the result is significantly different: a maximum of 13 cartridges may be administered, rounded down to the nearest half cartridge.² Note that the actual maximum number of cartridges that may be safely administered to patients in this example is not 13; the MRD is limited by the epinephrine content to 11 cartridges.⁴ When using the lower values, the drug that limits the maximum number of cartridges is the local anesthetic drug (first example of eight cartridges; 8<11). When using the FDA values, the limiting drug is epinephrine (second example of 11 cartridges; 11<13).

The use of articaine requires an important modification. The mg/lb MRD for articaine is the same in both sets of recommendations. Through at least 2010, product inserts for 4% articaine, 1:100,000 epinephrine list an absolute MRD of seven cartridges, which is approximately 500 mg.⁷ The current FDA recommendation lists a 3.2 mg/lb maximum, with no absolute maximum; however, there is a maximum limit of 4% articaine, 1:100,000 epinephrine, based on the epinephrine content of 11 cartridges.⁷ In addition to articaine insert changes, the current recommendation for 0.5% bupivacaine, 1:200,000 epinephrine, is an absolute maximum of 90 mg. MRD information for bupivacaine delineated by pound is no longer available in the US. In Canada, the recommendations for bupivacaine are 0.9 mg/lb and 2.0 mg/kg.²

Although the FDA has provided MRDs for local anesthetic drugs (Table 1), patient response to drug dosage cannot always be predicted. Two equal doses of the same anesthetic agent can produce markedly different responses in two different patients. Hyper-responders, for example, may respond to less than maximum doses with signs and symptoms of overdose. These individuals join a number of other patients who do not fit easily into dose recommendations, including those for whom typical doses result in finite, but relatively prolonged, periods of soft tissue anesthesia.

In addition to observing MRDs, the administration of local anesthetic drugs continues to be guided by several important factors, including the area to be anesthetized, vascularity of the tissues, technique, and individual tolerances. Perhaps the most important advice to follow comes from a similarly-worded statement that may be found in all local anesthetic product inserts:”The lowest dosage needed to provide effective anesthesia should be administered.”⁸

References

1. National Library of Medicine. Daily Med. Available at:http://dailymed.nlm.nih.gov/dailymed/drugList.cfm?startsWith=All. Accessed September 17, 2013.
2. Malamed S. Handbook of Local Anesthesia. 6th ed. St. Louis: Elsevier Mosby; 2013.
3. Malamed S. Handbook of Local Anesthesia. 5th ed. St. Louis: Elsevier Mosby; 2004.
4. Bassett K, DiMarco A, Naughton D. Local Anesthesia for Dental Professionals. Upper Saddle River, NJ: Pearson; 2009.
5. Malamed SF. What’s new in local anesthesia. Dimensions of Dental Hygiene. 2013:11(7):21–22.
6. American Academy of Pediatric Dentistry. Guideline on Use of Local Anesthesia for Pediatric Dental Patients. Available at: www.aapd.org/media/Policies_Guidelines/G_LocalAnesthesia.pdf. Accessed September 18, 2013.
7. Drug Information Online. Articaine and Epinephrine Injection. Available at: www.drugs.com/pro/articaine-and-epinephrineinjection. html. Accessed September 18, 2013.
8. National Library of Medicine. Daily Med: 4% articaine, 1:100,000 epinephrine product insert. Available at: dailymed.nlm.nih.gov/dailymed/archives/fdaDrugInfo.cfm?archiveid=28573. Accessed September 18, 2013.

From Dimensions of Dental Hygiene. October 2013;11(10):28–29,31.