Chemical structure and pharmacodynamics
The pharmacological profile of trimecaine (Trimecainum) is largely determined by its belonging to the class of amide local anesthetics. In its chemical structure, this substituted amide demonstrates a high degree of similarity to lidocaine. In medical practice, it is traditionally used in the form of hydrochloride.
For an objective assessment of the pharmacodynamic properties of the drug, it is customary to consider it in comparison with the reference ester-type anesthetic, procaine. As a result of this comparison, the following key features are revealed:
- Anesthetic activity: the drug demonstrates high potency, which exceeds the activity of procaine by 2–3 times.
- Duration of effect: characterized by a more prolonged clinical action. Anesthesia persists for 2 to 4 hours, making it convenient for prolonged procedures.
- Safety profile: the flip side of high activity is increased toxicity. It is reliably higher than that of procaine, which dictates the need for careful control of the administered dose.
Concentrations and types of anesthesia
The success of local anesthesia and patient safety directly depend on the correct choice of solution concentration. Trimecaine demonstrates varying efficacy depending on the route of administration, which is reflected in strict dosage regimens.
| Type of anesthesia | Recommended solution concentration |
|---|---|
| Infiltration | 0,125% – 0,5% |
| Conduction | 1% – 2% |
| Spinal | 5% |
Separately, surface (terminal) anesthesia should be considered. For this type of anesthesia, the drug is recognized as having low efficacy. To achieve even a minimal therapeutic effect on mucous membranes, very high concentrations of the solution are required — from 2% to 5%. However, even with such figures, it is significantly inferior to other, more specialized local anesthetics.
Resorptive effects and precautions
In addition to local action, upon absorption into the systemic circulation, the drug exerts a noticeable resorptive effect, primarily targeted at the central nervous system (CNS). The nature of this effect is strictly dose-dependent:
- At therapeutic doses, an inhibitory effect on the CNS predominates. Clinically, this is expressed as noticeable sedative and hypnotic effects.
- Upon intoxication (due to dose excess or accidental intravascular administration), the impact profile changes dramatically. There is a critical risk of developing severe neurological reactions, in particular — clonic seizures.
To minimize systemic absorption and prevent intoxication, special pharmacological precautions are applied. Standard practice is to add epinephrine to the anesthetic solution. This solves two tasks simultaneously: significantly reducing the overall toxicity of the drug and additionally prolonging its local anesthetic effect.
Briefly: answers to topical questions
What are the contraindications to the use of trimecaine?
Contraindications to the use of trimecaine are:
- hypersensitivity to trimecaine;
- sick sinus syndrome;
- atrioventricular (AV) block;
- pronounced bradycardia;
- cardiogenic shock;
- liver and kidney pathology.
Where and by what enzymes is trimecaine metabolized?
Trimecaine belongs to the amide group. Its biotransformation occurs in the liver with the participation of microsomal enzymes. It is not degraded by blood cholinesterase; inactivation occurs more slowly than that of ester-type local anesthetics.
What effect does trimecaine have on the cardiovascular system during resorptive action?
Upon resorptive action, trimecaine dilates blood vessels. In dental practice, it is used together with vasoconstrictors to slow down absorption. In cardiology, trimecaine is used for ventricular extrasystoles and tachyarrhythmia, similarly to lidocaine.
What is the maximum single dose of trimecaine for local anesthesia?
The maximum total dose of trimecaine for injection is 300 mg.
To memorize the resorptive effect on the CNS: TRImecaine — THREE phases: Inhibits (sedative effect), Relaxes (hypnotic effect), but during Intoxication — seizures.
Class and exam questions
Why is it necessary to add epinephrine to trimecaine?
The addition of epinephrine pursues two main goals: reducing the systemic toxicity of the drug by decreasing its absorption into the bloodstream and significantly prolonging the local anesthetic effect.
How much stronger is trimecaine than procaine in pharmacodynamic properties?
In terms of local anesthetic activity, it surpasses procaine by 2–3 times, providing reliable anesthesia lasting from 2 to 4 hours.
Is it advisable to use the drug for terminal anesthesia?
No, it is of low efficacy for surface (terminal) anesthesia. Even when using high concentrations (2–5%), it is inferior to other anesthetics, so it is generally not chosen for this purpose.
What else to study on this topic
- Features of the chemical structure of substituted amides and their difference from esters
- Comparative pharmacological profile of trimecaine and lidocaine
- Pathogenesis of clonic seizures in amide local anesthetic intoxication
- Pharmacodynamic interaction of local anesthetics and epinephrine
- Specifics of using 5% solutions in spinal anesthesia
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