Toxic effects of medicinal products

Types of overdose

The toxic effect is directly related to the concept of overdose, when an excessive concentration of the drug builds up in the tissues. There are two main mechanisms for the development of this condition:

• Absolute overdose. Occurs due to a direct violation of the dosing regimen. The patient is administered a dose that exceeds the established maximum single, daily, or course values. As a result, the concentration of the substance predictably reaches a dangerous level.
• Relative overdose. Develops against the background of taking standard therapeutic doses. The problem lies in the pathology of elimination organs. A decrease in the detoxifying function of the liver or the excretory function of the kidneys leads to the drug not being excreted in time. Long-term treatment with drugs prone to accumulation (cumulation) significantly increases the risk of relative overdose.

Organotoxicity (target organ damage)

An excess of a medicinal substance attacks specific systems, causing severe disruptions in their function. The most characteristic clinical examples:

1. Central nervous system (CNS). The main danger lies in the depression of vital centers of the medulla oblongata. A classic example is complete respiratory arrest during an opioid overdose.
2. Cardiovascular system. An excess of certain drugs disrupts the conduction of electrical excitation in the myocardium. A similar effect is typical for toxic doses of cardiac glycosides.
3. Liver (hepatotoxicity). The organ takes the main hit during drug metabolism. The toxic effect of, for example, Paracetamolum, can lead to impaired liver function up to massive necrosis.
4. Hematopoiesis (hematotoxicity). Drugs are capable of suppressing hematopoietic lineages. The use of an analgesic such as Metamizolum natrium is associated with the risk of developing leukopenia and agranulocytosis.

Specific types of toxicity

A special group consists of effects affecting the genetic apparatus and fetal development. The prescription of any medications to pregnant women requires strict medical supervision due to the risk of developmental anomalies or fetal death.

• Fetotoxic effect. The negative impact of the drug on the fetus in the later stages of pregnancy. During this period, organ formation (organogenesis) is already complete, so the substance directly attacks the functioning systems of the fetus. For example, anticoagulants reduce clotting and create a risk of bleeding in the newborn. Sulfonylurea derivatives provoke severe hypoglycemia, and neurotropic agents (alcohol, drugs, sleeping pills) sharply depress the child's CNS activity.
• Mutagenic effect. The ability of a substance to cause permanent mutations. The drug attacks germ cells at the stage of gametogenesis, as well as somatic cells of the developing embryo, altering their genetic code.
• Carcinogenic effect. The property of a drug to provoke the development of malignant neoplasms (cancer).

Safety requirements for new drugs

Pharmacology imposes strict safety requirements on new molecules. At the stages of preclinical studies and before introduction into practice, the presence of embryotoxic, teratogenic, fetotoxic, mutagenic, and carcinogenic properties in the developed agent is mandatory excluded. If a drug demonstrates such effects, its use in broad practice is unacceptable.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Mechanisms of paracetamol hepatotoxicity
• Pathogenesis of agranulocytosis upon administration of metamizole sodium
• The process of drug cumulation and its types
• Toxic effect of opiates on the respiratory center of the medulla oblongata
• Myocardial conduction disturbances against the background of excess cardiac glycosides

Other topics in "General Pharmacology"

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