chairside. If these products are supplied in a standard 1.7 mL dental cartridges, and at a cost more comparable to current non-buffered drugs, they could represent the next generation and new standard for local anesthetics in dentistry. In addition, removal of sodium chloride from the formulation will significantly reduce the current hypertonicity of buffered mixtures (approximately 217 mOsm/L), which will further contribute
to patient comfort. Perhaps most importantly, the possibility of local toxicity or sterility breaches due to current “chairside compounding” techniques will be completely eliminated. This is significant, as 8.4% sodium bicarbonate has an osmolality of 2,000 mOsm/L, and chairside compounding adds additional failure points in the sterility chain (Senewiratne, Woodall & Can, 2021).
LOCAL ANESTHETIC TOXICITY
Local anesthetics are relatively safe. However, repeated injections or even a single inadvertent intravascular injection can result in high systemic absorption, which could lead to toxicity. This is the primary reason that clinicians should aspirate prior to every injection. The signs and symptoms of local anesthetic toxicity are mainly neurologic in nature. Initially the patient may appear sedated or lightheaded, with slurred speech. These symptoms are very similar to the symptoms seen in the patient who develops hypoglycemia while in the dental chair, and this
differential diagnosis must be immediately ruled out or treated based on the patient’s medical history. Some patients can go on to develop diplopia (double vision), muscle twitching, or other sensory disturbances such as disorientation. At higher blood levels, local anesthetic toxicity can result in tremors, respiratory depression, and even tonic-clonic seizures. In severe cases, the local anesthetic overdose can result in respiratory or cardiovascular collapse or even coma. The maximum recommended doses for local anesthetics are shown in Table 7.
Table 7: Maximum Recommended Dosages for Local Anesthetics
Number of Carpules: Adults
Number of Carpules: 50-lb Child
Local Anesthetic
Maximum Dose 3.3 mg/lb (500 mg)
Lidocaine with 1:100,000 epinephrine (2%-36 mg)
13.8
4.6
Lidocaine with 1:50,000 epinephrine
3.3 mg/lb (500 mg)
5.5
NR*
Lidocaine without epinephrine
2.0 mg/lb (300 mg)
8.3
2.8
Mepivacaine (3% – 54 mg)
2.6 mg/lb (400 mg)
7.4
2.5
Mepivacaine (2% with 1:20,000 levonordefrin)
2.6 mg/lb (400 mg)
11.1
3.7
Prilocaine plain (4% – 72 mg)
8.3
2.8
4.0 mg/lb (600 mg)
Prilocaine with 1:200,000 epinephrine
8.3
2.8
Bupivacaine (0.5%)
0.6 mg/lb (90 mg)
10.0
NR
Articaine (4% – 72 mg)
3.3 mg/lb (500 mg)
6.9
2.3
Lidocaine with 1:100,000 epinephrine (2% – 36 mg)
3.3 mg/lb (500 mg)
13.8
4.6
Lidocaine with 1:50,000 epinephrine
3.3 mg/lb (500 mg)
5.5
NR
Lidocaine without epinephrine
2.0 mg/lb (300 mg)
8.3
2.8
*NR: Not recorded. Note . Adapted from “The ADA/PDR Guide to Dental Therapeutics” (5th ed.), by the American Dental Association and the Physicians’ Desk Reference, 2009, PDR Network, pp. 11-13; “Local Anesthetics: Review of Pharmacological Considerations,” by D. E. Becker and K. L. Reed, 2012, Anesthesia Progress, 59(2), pp. 90-102; “An Update on Local Anesthetics in Dentistry,” by D. A. Haas, 2002, Journal of the Canadian Dental Association, 68(9), pp. 546-551; “Management of Pregnant Patient in Dentistry,” by S. Kurien, V. S. Kattimani, R. R. Sriram, S. K. Sriram, V. K. P. Rao, A. Bhupathi, … N. Patil, Journal of International Oral Health, 5(1), 88-97; “Preventing Local Anesthesia Toxicity,” by P. A. Moore, (1992), Journal of the American Dental Association, 123(9), 60-64; “Local Anesthetics: Pharmacology and Toxicity,” by P. A. Moore and E. V. Hersh, 2010, Dental Clinics of North America, 54(4), pp. 587-599; and “Legal Considerations,” by D. J. Orr, II, 2013, in S. F. Malamed (Ed.), Handbook of Local Anesthesia (6th ed.), Elsevier Mosby, p. 350.
On May 23, 2018, the U.S. Food and Drug Administration issued a safety announcement warning consumers not to use teething products containing benzocaine in infants and children younger than 2 years (U.S. Food and Drug Administration, 2018). While this is a completely separate topic from the injectable local anesthetic formulations being discussed in this module, the importance of this warning bears mention. The announcement updates previous reports of benzocaine’s association with Cardiac patients Although local anesthetics themselves are relatively safe, solutions containing a vasoconstrictor may be considered less safe in cardiac patients (Guimaraes, et al., 2021). The current recommendations in clinical practice when managing high risk patients with cardiovascular disease include aspiration prior to injection; appropriate monitoring; behavioral modification such as lowering and raising the dental chair more gradually;
methemoglobinemia, and warns that benzocaine-containing products should not be used to treat infants and children younger than 2 years because they carry serious risks and provide little to no benefit for treating sore gums in infants due to teething. There have been more than 400 cases of benzocaine-associated methemoglobinemia reported to FDA since 1971, with 119 cases being reported just in the last 10 years.
SPECIAL POPULATIONS
and appropriate prescribing for dental treatment, such as prophylactic and restorative approaches rather than surgical intervention, if possible (Becker & Reed, 2012). The use of reasonable amounts of local anesthetic with minimally effective concentrations of epinephrine (not levonordefrin) is also recommended, although the 1:50,000 concentration of epinephrine should typically be avoided and practitioners should
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