Cocaine

Origin and chemical properties

The source of this alkaloid is a South American plant — the coca shrub (Erythroxylon coca). Chemically, the substance is an ester of benzoic acid and methylecgonine.

In pharmacological practice, the drug is obtained either by direct extraction from plant materials or semi-synthetically, using ecgonine as a base. For medical purposes, the soluble form, cocaine hydrochloride, is traditionally used.

Pharmacokinetics and local effects in ophthalmology

The substance is distinguished by high anesthetic activity. Its main pharmacokinetic feature is the ability to cross mucous membranes into the systemic circulation extremely rapidly. This very property determines its pronounced resorptive effect, which is often accompanied by severe toxic and side effects, making the drug hazardous for widespread use.

In ophthalmology, the drug is used extremely rarely. It is instilled directly into the conjunctival sac, where it provides local anesthesia lasting about one hour.

Local effects on the organ of vision:

• Pronounced constriction of the scleral blood vessels.
• Pupil dilation (mydriasis).
• Change in intraocular pressure (IOP): in most cases it decreases, but in predisposed patients, a sharp and dangerous spike in IOP may occur.
• Specific complication: with prolonged use of the drug, severe ulceration of the corneal epithelium develops.

Systemic effects on the body and toxicity

After absorption into the systemic circulation, the drug exerts a powerful stimulating effect on the central nervous system.

Psychotropic effects include the development of euphoria, pronounced psychomotor agitation, as well as a marked decrease in the sense of hunger, anxiety, and physical fatigue.

The substance actively affects the structures of the medulla oblongata, stimulating a number of vital centers:

1. Respiratory center.
2. Vasomotor center.
3. Vomiting center.

Cardiovascular effects manifest as tachycardia, systemic vasoconstriction (blood vessel narrowing), and elevated blood pressure. This symptom complex is realized through two main mechanisms: direct stimulation of the vasomotor center and potentiation of sympathetic influences (enhancement of excitatory effects of adrenergic innervation).

Toxic effect: in high doses, the drug causes seizure syndrome. As intoxication increases, the excitation phase is replaced by CNS depression. There is a critical risk of a fatal outcome due to respiratory arrest, which is associated with direct paralyzing depression of the respiratory center.

Emergency care for poisoning

Treatment of acute poisoning requires immediate action aimed at removing the toxin, preventing its further absorption, and stabilizing the patient's condition.

Decontamination (removal of the poison):

• If it comes into contact with mucous membranes, they must be washed abundantly with isotonic sodium chloride solution.
• If ingested, gastric lavage is performed using a weak potassium permanganate solution (0.05–0.1%), after which enterosorbents and saline laxatives are administered.

Limitation of systemic absorption:

• If the drug was administered by injection, a tourniquet must be applied immediately proximal to the injection site.

Symptomatic treatment:

• Diazepam is administered intravenously to stop psychomotor agitation and seizures.
• If signs of respiratory depression develop, the patient is transferred to mechanical ventilation.

Drug dependence (Cocaine addiction)

Chronic substance abuse (cocaine addiction) develops due to its specific psychotropic properties. The substance's appeal to addicts is due to the development of euphoria (elimination of negative emotions, a sharp lift in mood), as well as its ability to mask fatigue and temporarily increase working capacity.

Routes of administration: chronic use can be intranasal (inhalation of the powder), by chewing coca leaves, or via intravenous injection.

Withdrawal syndrome (abstinence): abrupt cessation of substance intake causes a severe condition in the patient. It is characterized by deep depression, severe physical and mental fatigue, and a distressing psychological background. As a result, highly pronounced psychological dependence is formed, overcoming which requires prolonged specialized care.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Mechanisms of potentiation of adrenergic innervation during systemic action
• Pathogenesis of corneal ulceration: trophic disorders during local anesthesia
• Features of differential diagnosis of seizure syndrome in poisonings
• Pharmacological rationale for the concentration of potassium permanganate during gastric lavage

Other topics in the "Analgesics" section

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