In practice, clinicians also need to remember that there is an absolute dose ceiling as well. Lidocaine, for example, has a maximum adult dose of about 500 mg per appointment. Even if a patient’s weight-based calculation suggests a higher amount could be given, the absolute maximum still applies. The rule is simple: always stay within whichever limit is lower. Local anesthetic systemic toxicity is rare, but it is one of the most serious complications associated with these drugs. Dr. Nkansah explains that anesthetics work by blocking electrical conduction. Their goal is to prevent action potentials in the target nerve, stopping pain transmission. Problems arise when significant concentrations reach other excitable tissues. “The first system that breaks down is the central nervous system,” he says. Early signs of toxicity may include perioral numbness, metallic taste or sensory changes. As blood concentrations rise, toxicity can extend into the cardiovascular system. Dr. Nkansah says that the brain and heart are the body’s major electrical organs, and high enough exposure can lead to seizures, cardiac depression and even cardiovascular collapse. Dr. Nkansah explains that treating the rare complication of local anesthetic systemic toxicity (LAST) can be difficult in a typical dental office because the antidote—IV lipid emulsion therapy, known as Intralipid®—is usually only available in hospital settings. That’s why, he says, “management is prevention.” Prevention starts with careful planning. Dentists need to review the patient’s medical history, calculate doses accurately, and recognize that people can respond differently to the same amount of anesthetic. Dr. Nkansah notes that some patients may become unusually drowsy or sensitive even at relatively low doses. Good injection technique is also essential. One important safety step is aspirating before injecting, since accidentally injecting into a blood vessel is a major cause of toxicity. As Dr. Nkansah puts it, “If you get a positive aspiration, don’t inject.” If toxicity does occur, the priority is to call emergency services immediately and transfer the patient to hospital care, where IV lipid emulsion therapy treatment may be available. Emerging Developments Dr. Nkansah concludes that buffering is one of the most promising advances in local anesthesia and something dentists can use right now. By adding a small amount of sodium bicarbonate, clinicians can raise the pH level of the anesthetic solution. This can make injections sting less and may help the anesthetic take effect more quickly. Looking to the future, Dr. Nkansah points to newer long‑acting anesthetics like ropivacaine and levobupivacaine. These drugs could offer the extended pain control of bupivacaine, but with less risk of cardiotoxicity. Although they are not yet available for dental use, they may represent the next generation of safer, longer-lasting anesthesia. Reference 1. Tan YZ, Shi RJ, Ke BW, Tang YL, Liang XH. Paresthesia in dentistry: The ignored neurotoxicity of local anesthetics. Heliyon. 2023 Jul 7;9(7):e18031 Dentists need to review the patient’s medical history, calculate doses accurately, and recognize that people can respond differently to the same amount of anesthetic. Learn more about the pharmacology of local anesthesia from Dr. Nkansah on CDA Oasis: bit.ly/4vjfWQ5 34 | 2026 | Issue 3 Supporting Your Practice
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