2. Local anesthetic substances. Classification. Mechanism of action. Indications for use. Side effects. Contraindications Comparative evaluation of drugs.

Local anesthetics - drugs that reversibly inhibit the excitation of afferent nerve endings, as well as the generation and conduction of nerve impulses along the fibers with the loss of all types of sensitivity.

Mechanism of action: they block voltage-gated sodium channels, prevent both the emergence of an action potential and its conduction.

Classification of local anesthetics

Aromatic acid esters	Aromatic amine amides
[Cocaine]	Lidocaine
Procaine (novocaine)	Trimecaine
Tetracaine (dicain)	Articaine (ultracaine)
Benzocaine (anesthesin)	Bupivacaine (marcaine)
Oxybuprocaine (inocaine)	Ropivacaine (Naropine)

Indications for the use of local anesthetics:

1. Infiltration anesthesia. Apply 0.25-0.5% solutions of procaine, 0.125-0.5% solutions of lidocaine, 0.125-0.25% solutions of bupivacaine. The duration of procaine anesthesia usually does not exceed 20-30 minutes, lidocaine - up to 1 hour, bupivacaine - more than 2 hours.

2. Conductive anesthesia. Use 1-2% solutions of procaine, lidocaine, articaine and 0.25-0.5% solutions of bupivacaine and ropivacaine. When repositioning dislocations, reposition of bone fragments, blockade of the trigeminal nerve, brachial, sacral plexuses.

3. Spinal anesthesia (subdural). It is more often produced with a 2-5% solution of lidocaine, sometimes with a 0.25-0.5% solution of bupivacaine or ropivacaine. In the absence of these drugs, procaine (5% solution) can be used. When carrying out lower-thoracic, urological operations.

4. Terminal anesthesia of the mucous membranes is achieved by using solutions of tetracaine (rarely), lidocaine or trimecaine (with the addition of epinephrine, preferably just before anesthesia).

5. Epidural anesthesia for abdominal operations, in obstetric and gynecological practice, in the postoperative period.

6. Lidocaine, trimecaine with ventricular extrasystole and tachycardia, especially with MI, prevention of ventricular fibrillation.

Comparative evaluation: by duration: long-term - anesthesin, pyromecaine, lidocaine, bupivacaine;

short-acting - cocaine, novocaine, dicaine; toxicity: the most toxic dicain, less toxic - novocaine, mepivacaine, pyromecaine.

Contraindications: hypersensitivity to drugs, decompensated heart failure, severe organic lesions of the central nervous system, septicemia.

Side effects:

1. drowsiness, lethargy, dizziness, impaired consciousness, thermor, convulsions;

2. tachycardia, bradycardia, decreased A, arrhythmias, collapse;

3. blurred vision, diplopia;

4. allergic reactions;

5. respiratory depression.

3. Preparations of fat-soluble vitamins. Classification. Mechanism of action. Indications for use. Side effects. Contraindications Comparative evaluation of drugs.

Retinol, Betacarotene (Vitamin A)- found in fish oil, liver, cow oil. Enzymatic cleavage of one beta-carotene molecule leads to the formation of 2 molecules of Vitamin A. Mechanism: plays an important role in redox processes, participates in the synthesis of mucopolysaccharides, proteins, lipids. It is absorbed in the small intestine, enters the liver through the lymphatic pathways, retinol released into the blood in the plasma binds to proteins.

It is important for photoreception. In case of insufficiency, hemerolapia develops, damage to the mucous membranes and skin.