available bupivacaine in dental cartridges. The most recent published systematic review and meta-analysis on this subject concurs that, “The overall evidence level was low [for the safety of local liposomal bupivacaine infiltration], which means that further research is likely to significantly alter confidence levels in the effect, as well as potentially changing the estimated value”
(Zhang, Yang, & Zhang, 2017). A Cochrane review published later that same year had very similar conclusions (Hamilton et al., 2017). The following year Goodchild and Donaldson answered the question, “Does liposomal bupivacaine fulfill an unmet need in dentistry?” with an emphatic “no” based on current evidence (Goodchild & Donaldson, 2018a).
VASOCONSTRICTORS
The addition of a vasoconstrictor to a local anesthetic delays the drug’s vascular absorption and increases the duration of drug contact with nerve tissues. The overall effect is prolongation of the blockade by as much as 50% and a decrease in the systemic absorption of local anesthetic, which improves the overall safety. Dental treatment with insufficient vasoconstriction within the local anesthetic formulation can result in less than adequate pain control and increased levels of endogenous catecholamines, which can add to the patient’s discomfort and anxiety. Ineffective pain control increases patient health outcomes risk because a Epinephrine Epinephrine is the most common vasoconstrictor and is combined with local anesthetics in formulations of 1:50,000, 1:100,000, and 1:200,000. Concentrations above 1:200,000 do not offer any additional advantage in prolonging the local anesthetic effect or in reducing blood concentrations of the local anesthetic. Higher concentrations also do not provide a faster onset or longer duration of action following inferior alveolar nerve block or in reducing blood concentrations of the local anesthetic (Dagher, Yared, & Machtou, 1997; Scott, Jebson, Braid, Ortengren, & Frisch, 1972; Tófoli, Ramacciato, de Oliveira, Volpato, & Ranali, 2003). However, greater concentrations (e.g., 1:100,000 and 1:50,000) may be used to levonordefrin Levonordefrin is the second most common vasoconstrictor used in dental cartridges. It is combined with local anesthetics as a 1:20,000 solution, which is equivalent to 1:100,000 epinephrine in terms of alpha receptor activity (vasoconstriction). It is the vasoconstrictor present in 2% mepivacaine. Following infiltration, levonordefrin and epinephrine have similar efficacy in constricting submucosal vessels, and their effects on local hemorrhage and anesthetic absorption are equivalent. Structurally, levonordefrin resembles norepinephrine and therefore lacks beta-2 receptor activity (resulting in less vasodilation of blood vessels in the skeletal muscle). Whereas Table 6: Maximum Recommended Dosages of Vasoconstrictors Concentration
rise in endogenous catecholamines increases blood pressure and can have other cardiotoxic effects. Vasoconstriction may be more important for infiltration injections in vascular sites compared to mandibular blocks, as the presence of a vasoconstrictor can also help to provide local hemostasis (decreased bleeding). For example, on a clinical note, if a patient presents with postoperative bleeding from an extraction site, administering local anesthetic with a vasoconstrictor often stops the bleeding without the need for any other intervention. provide better hemostasis at the surgical site, when this effect is desired. Epinephrine causes vasoconstriction by stimulating alpha-1 receptors in mucous membranes. It also stimulates beta-1 receptors in the heart (increasing heart rate, strength of contraction, and myocardial oxygen consumption) and the beta-2 receptors, resulting in vasodilation of blood vessels in the skeletal muscle. Drug interactions with epinephrine tend to be the result of use with drugs that affect these same receptors. These drugs include non-selective beta-blockers such as propranolol (Inderal) and metoprolol (Toprol), tricyclic antidepressants such as amitriptyline (Elavil) and desipramine (Norpramin), general anesthetics, and cocaine. epinephrine can increase heart rate and systolic pressure but lower diastolic pressure based on beta-2 stimulation, levonordefrin increases systolic, diastolic, and mean arterial pressures, which triggers a reflex slowing of heart rate (Westfall & Westfall, 2011). Because of this property, levonordefrin has been suggested as an alternative to epinephrine-containing local anesthetics when treating patients with cardiovascular heart disease. However, this drug does exert an undesirable influence on blood pressure. The maximum recommended doses for vasoconstrictors are shown in Table 6.
Maximum Recommended Dosage
Parts per Thousand 1:50,000*
Number of Carpules
mg/mL
mg 0.2
mL
0.02
10
5
Epinephrine
0.01
1:100,000
0.2
20
11
0.005
1:200,000
0.2
40
11 †
Levonordefrin
0.05
1:20,000
1.0
20
11
* 1:50,000 should be reserved for local hemostasis. † Maximum number of carpules is limited by the local anesthetic.
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; “Preventing Local Anesthesia Toxicity,” by P. A. Moore, 1992, Journal of the American Dental Association, 123(9), pp. 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; “Legal Considerations,” by D. J. Orr, II, 2013, in S. F. Malamed (Ed.), Handbook of Local Anesthesia (6th ed.), Elsevier Mosby, p. 350; and “Adrenergic Agonists and Antagonists,” by T. Westfall and D. P. Westfall, 2011, in L. L. Brunton, B. A. Chabner, & B. C. Knollmann (Eds.), Goodman and Gilman’s The Pharmacological Basis of Therapeutics (12th ed.), McGraw-Hill, pp. 277-334.
Page 158
EliteLearning.com/Dental
Powered by FlippingBook