Amide anesthetic group
Amide drugs are the most active modern agents for achieving effective pain relief. Compared to esters, they have several key advantages:
- faster onset of action;
- longer duration of effect;
- broader zone of anesthesia;
- better diffusion into tissues directly at the injection site.
The main representatives of this group include lidocaine, mepivacaine, and articaine. The group also includes trimecaine, prilocaine, etidocaine, bupivacaine, and ropivacaine, although not all of them find wide application specifically in dental practice.
Articaine: drug of choice in dentistry
Articaine (Articainum) stands out among other amides due to its unique chemical structure. To achieve reliable anesthesia in dentistry, its 4% solution is typically used, which has been made possible by the drug's low toxicity.
Pharmacokinetic features of articaine:
- Has the highest plasma clearance among amides (3.9 L/min).
- Features the shortest half-life (depends on the amount of vasoconstrictor).
- Practically does not accumulate in the body upon repeated administrations, which is extremely convenient for large-volume dental procedures.
- Has lower lipid solubility compared to lidocaine, reducing the risk of systemic absorption.
Due to a high therapeutic index (optimal balance of efficacy and toxicity), the drug is the priority choice for children, the elderly, nursing mothers, and patients with renal or hepatic pathology. High local anesthetic activity allows reducing the concentration of the added vasoconstrictor to 1:200,000.
Properties and pharmacodynamics of procaine
Procaine has moderate analgesic activity. In its pure form, the drug anesthetizes soft tissues for 15–30 minutes, and with a vasoconstrictor, the effect is extended up to 60 minutes. About 33% of its metabolite (diethylaminoethanol) is excreted unchanged, while the rest undergoes biotransformation.
An important feature of procaine is its most pronounced vasodilatory effect among analogues. Due to strong vasodilatation, it requires the addition of high concentrations of adrenaline. A vasoconstrictor is necessary to prolong anesthesia and reduce capillary bleeding.
The drug is capable of exerting a systemic resorptive effect. Upon entering the bloodstream, it:
- depresses the central nervous system and decreases the excitability of motor cortical areas;
- decreases myocardial excitability (antiarrhythmic effect);
- inhibits acetylcholine production (ganglion-blocking effect);
- depresses spinal reflexes.
Procaine is also actively used for therapeutic blocks. When infiltrating a pathological focus, it reduces the sensitivity of interoreceptors, interrupts pathological autonomic reflexes, improves microcirculation, and exerts a beneficial effect on the neurotrophic component of inflammation.
Limitations and symptoms of overdose
The use of procaine is contraindicated in hypersensitivity, sulfonamide therapy, myasthenia gravis, pseudocholinesterase deficiency, and hypotension. The drug is allergenic, and its use in risk-group patients is undesirable.
It is important to remember that at the same total dose, the toxicity of the drug increases proportionally with the increase in the concentration of its solution. The mechanism of overdose is associated with impaired neuromuscular transmission and reduced acetylcholine release. Symptoms progress as the concentration increases:
- Dizziness and paresthesia.
- Motor agitation.
- Convulsions (including epileptiform ones).
- Dyspnea and collapse.
Briefly: answers to topical questions
What are the pharmacological properties and duration of action of procaine?
Procaine has moderate local anesthetic activity, a wide therapeutic index, and a pronounced vasodilatory effect. Pharmacological properties include:
- Local action — moderate anesthesia, improvement of microcirculation.
- Systemic action — antiarrhythmic, antispasmodic, analgesic, antishock, antipruritic, and ganglion-blocking.
- CNS effects — depresses the nervous system and decreases the excitability of motor cortical areas.
- Interaction — weakens the antimicrobial action of sulfonamides and requires the addition of vasoconstrictors due to vasodilation.
The duration of soft tissue anesthesia in pure form ranges from 15 to 30 minutes. With the addition of a vasoconstrictor (adrenaline), the duration of action increases to 60 minutes.
What are the maximum doses of local anesthetics for dental use?
Maximum doses of local anesthetics depend on the specific drug, its concentration, and the patient's age.
| Drug | Maximum dose |
|---|---|
| Procaine | 500 mg (without vasoconstrictor) |
| Mepivacaine | 4.4 mg/kg, but not more than 300 mg |
| Articaine (Articainum) | Adults — 7 mg/kg, children — 5 mg/kg |
| Tetracaine | 0.09 g (for adults) |
For trimecaine, the dosage depends on the concentration: 2% solution — up to 20 ml, 1% — up to 100 ml, 0.5% — up to 400 ml, 0.25% — up to 800 ml. When using articaine, it is clinically recommended to administer no more than half of the maximum permissible dose.
Class and exam questions
Why is procaine not used for topical (surface) anesthesia?
It penetrates tissues very poorly and, at the high concentrations (10–20%) required for topical application, exhibits a pronounced irritant effect.
Why is adrenaline added to local anesthetics?
A vasoconstrictor (adrenaline) compensates for the vasodilatory action of anesthetics. It enhances and prolongs pain relief and also reduces capillary bleeding during surgery.
Which drug is the safest to use for a nursing mother?
The optimal choice is articaine. It is rapidly metabolized, does not accumulate, and is not detected in breast milk in clinically significant concentrations.
What else to study on this topic
- Mechanism of action of procaine in therapeutic blocks
- Systemic (resorptive) effects of local anesthetics on the central nervous and cardiovascular systems
- Comparative characteristics of plasma clearance of various amide anesthetics
- Features of articaine use in intraosseous and intraligamentary anesthesia
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