Local anaesthetics are among the most frequently used medicines in dentistry. They are also capable of causing a rare but potentially life-threatening emergency: local anaesthetic systemic toxicity (LAST).
LAST occurs when the concentration of a local anaesthetic in the bloodstream becomes high enough to affect the central nervous and cardiovascular systems. Severe toxicity can lead to seizures, arrhythmias, cardiovascular collapse and death.
For dentists, preventing LAST is not simply a matter of staying below a maximum recommended dose. Safe practice also requires careful injection technique, consideration of patient-specific risk, awareness of cumulative dosing when more than one local anaesthetic is used, early recognition of toxicity and a rehearsed emergency response.
Recent pharmacovigilance evidence has made this subject particularly relevant. Fettiplace and colleagues analysed 55 years of US FDA adverse-event reports involving local anaesthetics and identified 22,050 reported adverse events and 1,473 deaths. Reported deaths involving bupivacaine and ropivacaine declined following modern practice advisories, while the same improvement was not seen with lidocaine.
For dental teams, the message is not to fear local anaesthesia. It is to use it with precision.
What Is Local Anaesthetic Systemic Toxicity?
Local anaesthetic systemic toxicity occurs when excessive concentrations of a local anaesthetic enter the systemic circulation.
This may occur because of:
- inadvertent intravascular injection;
- administration of an excessive total dose;
- rapid absorption from a highly vascular site;
- repeated doses during a prolonged procedure; or
- cumulative exposure when multiple local anaesthetic agents are used.
Once circulating concentrations become sufficiently high, local anaesthetics can interfere with ion channels in the brain and heart.
The result can be progressive neurological and cardiovascular toxicity.
Importantly, LAST is not restricted to hospitals or anaesthetic practice. It can occur following dental local anaesthetic administration, including during routine blocks and more complex oral surgery or implant procedures.
Can LAST Occur Below the Maximum Recommended Dose?
Yes.
This is one of the most important principles for dentists to understand.
A maximum recommended dose is designed to reduce the risk of systemic toxicity from the total administered dose. It does not guarantee that toxicity cannot occur below that amount.
For example, inadvertent intravascular injection can cause the blood concentration of a local anaesthetic to rise extremely rapidly.
The planned total dose may therefore be within recommended limits while the patient still develops systemic toxicity.
This is why LAST prevention requires more than calculating the number of cartridges.
Appropriate injection technique, aspiration where indicated, slow incremental administration, communication with the patient and observation for early symptoms remain important.
Maximum Local Anaesthetic Doses in Dentistry
Maximum recommended doses (MRDs) should be regarded as safety ceilings rather than treatment targets.
The lowest effective dose should always be used.
Clinicians should also consider factors that may alter an individual patient’s susceptibility, including age, body weight, pregnancy, frailty, significant cardiovascular or hepatic disease and relevant medicines.
Lignocaine: Why Dentists May See Different Maximum Doses
One important issue highlighted in the 2026 review is the discrepancy between commonly referenced maximum doses for lignocaine with adrenaline.
BNF 91 specifies 7 mg/kg up to a maximum of 500 mg for lignocaine with adrenaline.
However, UK product information may provide the more conservative figure of 4.4 mg/kg up to 300 mg.
That difference can be clinically relevant.
Rather than simply memorising one figure, dentists should know which current authoritative reference and product information apply to the local anaesthetic being administered.
The calculation should also take account of the vasoconstrictor dose.
Local Anaesthetic Dose Reference
| Local anaesthetic | Maximum dose discussed in the review | Important consideration |
|---|---|---|
| Lignocaine 2% with adrenaline | BNF/FDA: 7 mg/kg, maximum 500 mg | Some UK product information uses the more conservative 4.4 mg/kg / 300 mg ceiling |
| Articaine 4% with adrenaline | 7 mg/kg | Calculate according to body weight and the exact product used |
| Bupivacaine 0.5% | Review discusses a 2 mg/kg / 90 mg dental ceiling | Greater cardiovascular toxicity makes careful dosing particularly important |
These figures are a clinical reference rather than a substitute for checking the current BNF and Summary of Product Characteristics (SmPC) for the exact preparation being used.
Remember the Adrenaline Dose
The maximum local anaesthetic dose is only one part of the calculation when a preparation contains adrenaline.
The vasoconstrictor dose must be considered separately.
The review discusses an adrenaline ceiling of approximately 200 micrograms for healthy adults, with substantially lower exposure appropriate for selected patients with cardiovascular risk.
The practical maximum number of cartridges may therefore be determined by the adrenaline dose before the local anaesthetic MRD is reached.
In other words, dentists should ask two separate questions:
- How much local anaesthetic can this patient safely receive?
- How much vasoconstrictor can this patient appropriately receive?
Whichever limit is reached first becomes the practical ceiling.
Using More Than One Local Anaesthetic: The Fractional Dose Rule
Using more than one local anaesthetic during the same procedure introduces another important safety consideration.
Lignocaine, articaine and bupivacaine should not be treated as though each provides a completely separate toxicity allowance.
Their systemic toxic effects are additive.
A useful approach discussed in the review is the fractional dose rule:
(Dose of Agent A ÷ MRD of Agent A) + (Dose of Agent B ÷ MRD of Agent B) ≤ 1
If a third local anaesthetic is administered, its fractional contribution is added to the calculation.
Example
Suppose a dentist administers:
- three 2.2 mL cartridges of lignocaine 2% = 132 mg; and
- two 2.2 mL cartridges of articaine 4% = 176 mg.
Using conservative ceilings of 300 mg for lignocaine and 490 mg for articaine:
132 ÷ 300 = 0.440
176 ÷ 490 = 0.359
Combined fractional dose:
0.440 + 0.359 = 0.799
The cumulative fractional dose is therefore approximately 80% of the combined ceiling.
This calculation provides a practical way to account for additive systemic toxicity.
However, being below 1.0 should not be interpreted as a guarantee that LAST cannot occur. Intravascular injection and individual patient susceptibility remain important.
Why Long Implant Procedures Need Particular Attention
Modern full-arch implant surgery presents a dosing challenge that differs from a routine extraction or short restorative appointment.
A full-arch procedure may last several hours. Bimaxillary surgery may take even longer.
During an extended procedure, local anaesthetic may be:
- administered at the beginning;
- topped up as anaesthesia diminishes;
- administered to different anatomical regions;
- supplemented with another agent; and
- used again around wound closure.
Each additional dose may appear small.
The problem is the cumulative dose.
When a case lasts several hours, relying on memory is an unnecessary risk.
Use a Pre-Operative Local Anaesthetic Dose Budget
For prolonged implant or oral surgery procedures, consider establishing a dose budget before treatment begins.
A practical system should:
- Calculate the patient-specific maximum dose for each proposed agent.
- Calculate the relevant vasoconstrictor limit.
- Allocate anticipated doses by anatomical region or surgical stage.
- Record every local anaesthetic administration.
- Record the time at which each dose is administered.
- Maintain a running cumulative total.
- Apply a fractional-dose calculation if multiple agents are used.
- Reassess the need for additional anaesthetic before every top-up.
A named member of the clinical team can help maintain the running record during lengthy procedures.
What Are the Early Signs of Local Anaesthetic Toxicity?
LAST does not always follow the classic sequence taught in textbooks.
Possible early neurological symptoms include:
- metallic taste;
- circumoral or tongue numbness;
- tinnitus;
- dizziness;
- visual disturbance;
- agitation or altered behaviour;
- muscle twitching; and
- confusion.
More severe neurological toxicity may progress to seizures and loss of consciousness.
Cardiovascular toxicity can include:
- changes in blood pressure;
- conduction abnormalities;
- bradycardia or tachyarrhythmias;
- ventricular arrhythmias;
- cardiovascular instability; and
- cardiac arrest.
Some patients may develop cardiovascular features without an obvious neurological warning phase.
A close temporal relationship between local anaesthetic administration and new neurological or cardiovascular symptoms should therefore raise suspicion.
LAST or a Vasovagal Episode?
This distinction can be difficult because vasovagal syncope is common in dentistry and some early symptoms can overlap.
A typical vasovagal episode may involve pallor, sweating, nausea, bradycardia and rapid improvement after appropriate positioning.
LAST is more concerning when symptoms progressively worsen or neurological features such as tinnitus, metallic taste, circumoral numbness, agitation or seizure develop.
Other differential diagnoses include:
| Condition | Features that may help distinguish it |
| Vasovagal syncope | Pallor, sweating, bradycardia and usually rapid recovery with appropriate positioning |
| Adrenaline reaction | Palpitations, tachycardia, tremor and often transient hypertension without progressive neurological toxicity |
| Hypoglycaemia | Relevant medical history, sweating, confusion and improvement following glucose |
| Anaphylaxis | Urticaria, flushing, bronchospasm, wheeze or angioedema |
| Oversedation | Predominantly CNS and respiratory depression in a sedation context |
When the diagnosis is uncertain and symptoms are serious or progressive, patient safety should take priority over diagnostic certainty.
How Should Dentists Manage Suspected LAST?
The first minutes are critical.
1. Stop injecting immediately
Stop administration of the local anaesthetic.
Preventing any further systemic exposure is the immediate priority.
2. Call for help
Activate the practice emergency response.
For serious, progressive neurological or cardiovascular symptoms, call 999/112 and arrange urgent transfer.
3. Manage airway and breathing
Maintain a patent airway and administer high-concentration oxygen.
Support ventilation when required.
Avoiding hypoxia and acidosis is particularly important because both can worsen local anaesthetic toxicity.
4. Monitor the patient
Monitor oxygen saturation, blood pressure and pulse where equipment is available.
Establish intravenous access when this falls within the clinician’s training and the clinical setting.
5. Treat seizures appropriately
Benzodiazepines are generally used to control seizures associated with LAST.
Clinicians should follow current emergency guidance and administer medicines only within their training, competence and local protocol.
6. Treat cardiovascular collapse as a medical emergency
If cardiovascular instability or cardiac arrest develops, begin resuscitation immediately.
LAST requires specific considerations during advanced life support, including modification of some standard drug choices and doses.
A current LAST emergency algorithm should therefore be immediately accessible rather than relying on memory during a rare emergency.
7. Arrange hospital assessment
Significant neurological or cardiovascular LAST requires appropriate emergency assessment and observation.
What Is Intralipid and How Is It Used for LAST?
Intravenous lipid emulsion (ILE), commonly available as a 20% lipid emulsion, is an important rescue treatment for severe local anaesthetic systemic toxicity.
It is particularly relevant when LAST produces serious cardiovascular instability.
Lipid therapy is thought to reduce the amount of active lipophilic local anaesthetic available to affect cardiac and neural tissues, while additional metabolic and haemodynamic mechanisms may also contribute.
Importantly, lipid emulsion does not replace basic resuscitation.
Airway management, oxygenation, ventilation, seizure control, cardiovascular support and emergency transfer remain essential.
The Association of Anaesthetists regimen discussed in the review uses an initial 1.5 mL/kg bolus of 20% lipid emulsion, followed by an infusion, with additional dosing if cardiovascular stability is not restored.
Because emergency protocols can change, clinicians should use the current displayed LAST guideline rather than relying on a blog article as an emergency dosing card.
Whether intravenous lipid emulsion should be stocked in a particular dental setting should be determined by the procedures performed, doses administered, sedation arrangements, applicable professional standards and local risk assessment.
Five LAST Safety Changes Dental Practices Can Make
1. Create a local anaesthetic dose reference
Build a reference using the exact products and cartridge sizes stocked in the practice.
Include local anaesthetic concentration, milligrams per cartridge, vasoconstrictor content and applicable dose ceilings.
2. Calculate before complex procedures
Do not wait until several cartridges have already been administered.
Calculate the patient-specific dose budget before prolonged or multi-agent procedures.
3. Track every top-up
For long procedures, record the drug, concentration, volume and time of every administration.
4. Review the emergency kit and protocol
Check whether the practice’s emergency equipment and medicines are appropriate for the procedures being undertaken.
Ensure current LAST guidance is readily accessible.
5. Run a LAST simulation
Because LAST is rare, many clinicians will never have managed a real case.
Simulation allows the team to rehearse stopping the injection, summoning help, managing the airway, providing oxygen, controlling seizures, supporting circulation and handing the patient over to emergency services.
Frequently Asked Questions About LAST in Dentistry
Can LAST occur even if I stay below the maximum dose?
Yes. Inadvertent intravascular injection can cause a rapid increase in circulating local anaesthetic concentration even when the total administered dose remains below the MRD.
What is the maximum dose of lignocaine in dentistry?
The answer depends on the preparation and reference being followed. The 2026 review notes that BNF 91 specifies 7 mg/kg up to 500 mg for lignocaine with adrenaline, while relevant product information may use the more conservative 4.4 mg/kg up to 300 mg. Always check the current BNF and SmPC for the product being administered.
Can I use lignocaine and articaine in the same dental procedure?
Multiple amide local anaesthetics may be used sequentially in clinical practice, but their systemic toxicity should be regarded as additive. The combined exposure should therefore be considered rather than treating each MRD independently.
Does aspiration prevent LAST?
Aspiration can help reduce the risk of intravascular administration but does not eliminate it. Appropriate injection technique, slow incremental administration, dose calculation and patient monitoring remain important.
What are the first signs of LAST?
Possible early symptoms include metallic taste, circumoral or tongue numbness, tinnitus, dizziness, visual disturbance, agitation and other neurological changes. However, presentation can be atypical and cardiovascular signs may occasionally occur first.
Is Intralipid an antidote for local anaesthetic toxicity?
Intravenous lipid emulsion is an established rescue treatment for severe LAST, particularly cardiovascular toxicity. It should be used as part of a complete emergency response and does not replace airway management, oxygenation, resuscitation or emergency transfer.
Should every dental practice stock intravenous lipid emulsion?
This depends on the procedures undertaken, local anaesthetic exposure, sedation arrangements, professional standards and local risk assessment. Practices administering potentially cardiotoxic doses should review current Association of Anaesthetists, Resuscitation Council UK, SAAD and local governance guidance.
The Bottom Line
Local anaesthetic systemic toxicity is rare, but its consequences can be severe.
Preventing LAST in dentistry requires more than staying below a number printed in a dosing table. Dentists should calculate patient-specific doses, consider vasoconstrictor exposure, recognise the additive toxicity of multiple local anaesthetics, track cumulative doses during prolonged procedures and use careful injection technique.
Teams should also be able to recognise the early neurological and cardiovascular signs of LAST and respond according to a rehearsed emergency protocol.
Recent pharmacovigilance evidence concerning lidocaine-associated mortality reinforces a simple principle: familiarity with a medicine should never lead to complacency.
The maximum recommended dose is a safety ceiling, not a target. The lowest effective dose should always be used.
Before administering a local anaesthetic, clinicians should be able to answer two questions:
What is the appropriate maximum dose for this patient and this product?
How much local anaesthetic has this patient already received?
References and Further Reading
- Ucer C, Wright S, Khan R, Kumar S. Local Anaesthetic Systemic Toxicity in Dental and Oral and Maxillofacial Surgery: Safe Dosing, Combination Agents, and Emergency Management—A Narrative Review. Dentistry Journal. 2026;14(7):457.
- Fettiplace MR et al. Contemporary local anaesthetic-associated adverse events and mortality: a pharmacovigilance analysis of a US reporting system. British Journal of Anaesthesia. 2025;135:1015–1025.
- Neal JM et al. The Third ASRA Practice Advisory on Local Anesthetic Systemic Toxicity. Regional Anesthesia and Pain Medicine. 2018;43:113–123.
- Association of Anaesthetists. Management of Severe Local Anaesthetic Toxicity.
- British National Formulary. BNF 91. BMJ Group and Pharmaceutical Press, 2026.
- SAAD. Guidance on Conscious Sedation for Dentistry. 2026.
Clinical disclaimer: This article is intended for professional education and does not replace the current BNF, product SmPCs, Resuscitation Council UK or Association of Anaesthetists guidance, local clinical protocols, or individual patient assessment.
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