Why is adrenaline added to the local anesthetic


Symptoms of poisoning occur when the blood level exceeds a certain level.


Overdose: There is no precisely defined limit dose for the individual local anesthetics because it is not the locally administered dose but the blood concentration that is decisive.

As a rule of thumb, adults (body weight 70 kg) can tolerate 400 mg of 2% lidocaine (20 ml) or 400 to 600 mg of 4% articaine (10 to 15 ml) with subcutaneous injection, provided that adrenaline is used as a vasoconstrictor in a concentration of 1: 100,000 or 1: 200,000 or another vasoconstrictor is added in an appropriate concentration.

The limit dose for adrenaline is 0.2 mg. At a concentration of 1: 100,000, adrenaline is the limiting factor, at 1: 200,000 the local anesthetic.

The limit dose for the local anesthetic applies to subcutaneous injections outside the oral cavity.

For children, the maximum dose must be calculated individually based on body weight.

If a surface anesthetic is also used, the injection dose must be reduced accordingly.

Accelerated absorption:

In the more vascularized oral cavity area, the rate of resorption is higher than in other parts of the body. The doses specified for subcutaneous application must therefore not be fully used in the dental field.

Particularly rapid absorption must be expected when injecting into acutely inflamed hyperemic tissue.

The addition of adrenaline reduces the rate of absorption.

A higher concentration of the local anesthetic accelerates the absorption.

If the injection is slow, the added vasoconstrictor has more time to seal off the injection site by constricting the blood vessels.

A surface anesthetic is absorbed very quickly. More than two sprays should therefore not be applied.

Intravascular injection:

An accidental intravascular injection is of particular importance as a triggering factor for intoxication, because even small doses can cause a rapid rise in blood levels.

It is therefore necessary, after placing the cannula, to make sure by repeated aspiration that no vessel has been pierced. This occurs most frequently during conduction anesthesia of the mandibular foramen.


Symptoms of the central nervous system (CNS), vegetative and cardiovascular system (CVS) occur:

Arousal phase:

  • CNS: restlessness, ringing in the ears, dizziness, delirium, convulsions that turn into massive stretching convulsions with cyanosis.
  • Vegetative: sweat, nausea, vomiting.
  • CVS: tachycardia, increase in blood pressure, reddening of the skin.

Paralysis phase:

  • CNS: loss of consciousness, coma, motor and sensory paralysis, respiratory paralysis.
  • Vegetative: profuse sweat, patient leaves.
  • Pallor, cardiac arrest.
  • In the case of severe intoxication, the excitation phase can go through so quickly that it does not appear clinically. The patient becomes pale and in a short time falls into a coma.


  • Call an emergency doctor if cramps occur!
  • At the same time, action must be taken immediately:

In the arousal phase:

  • Intravenous injection of 5 to 10 mg midazolam (Dormicum), then 1 to 2 mg every two minutes until the cramps are released.
  • Alternatively: Initial injection of 10 to 15 mg intralingually.
  • In children, 0.15 to 0.2 mg / kg body weight intralingually.
  • Oxygen ventilation with a breathing bag to compensate for the increased need for oxygen due to the cramps.

In the paralysis phase:

  • Depression of the head.
  • Intravenous injection of 1 ml of Akrinor.
  • Creating an infusion.
  • Resuscitation measures in the event of cardiac arrest.


Strict observance of the limit dose.

Insertion of a venous cannula after exceeding 25% * of the limit dose.

Have midazolam and infusion solution ready.

Have a ventilator ready and the possibility of oxygen ventilation.

Injections into hyperemic, inflamed tissue should only be administered in small amounts.

Local anesthetics also have a sedative effect. Injecting larger doses may impair your ability to drive.

It is therefore recommended that patients after local anesthesia are not allowed to drive home in their own motor vehicle if a third of the limit dose has been exceeded.

Before a patient leaves the practice, they should wait until the analgesia has subsided.


* Recommendation of the Drugs Commission of the German Medical Association.