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The healing and toxic effects of chemical substances

Almost all chemicals can have a positive or negative (toxic) effect on the human body. The substance's action on the body is connected with its chemical structure and physicochemical properties as well as the amount administered into the body.

• Compounds easily soluble in water and easily dissociating are usually more active, because these are more quickly involved in metabolic processes in our body.

• The degree of substance fragmentation is also important, and this applies not only to dissolution processes, for example asbestos dust is harmful if its particles have a diameter less than 1 μm (1 µm = 10Indeks górny -6^-6 m) – inhaled causes pneumoconiosis, which leads to lung cancer.

• An important role is played by the shape of the molecule (mutual arrangement of the atoms that build it), because the course of many processes in organisms requires a very precise spatial matching of the reacting molecules of chemical compounds.

Not only are the properties important, but also the amount and concentration of the substance administered into the body – dosedosedose and the manner of its percolation into the body. For medicinesmedicinemedicines, the therapeutic dose is determined, i.e. the smallest amount of substance that produces the desired therapeutic effect, without causing serious disturbances in the metabolism of the body.

In toxicology, the dose amounts are determined in relation to the harmful effects of the substance (poison) on the body.

Toxic properties of substances (poisons) are determined on the basis of lethal dose LDIndeks dolny 50₅₀ (Latin dosis letalis), i.e. the amount that causes the death of half of test subjects in the group, and the toxic dose TD (Latin dosis toxica), i.e. the amount of substance that causes pronounced toxification of the body .

Chemical substances can get into our body in various ways, for example through the respiratory tract (aerosols), through the digestive system (powders, liquids) and through the skin and mucous membranes (ointments).

Painkillers

Acetylsalicylic acid (ASA) – one of the first painkillers in the world. Since ancient times people made medicines from plants. In antiquity, cold or rheumatism were treated with extracts from willow bark or raspberry juice. Both of these peculiarities contain salicylates – derivatives of salicylic acid.

Currently, acetylsalicylic acid and its compounds hit the market in the pharmacies under the name aspirin. Aspirin is one of the most popular drugs used in the pharmacology of 20th century.

The analgesic effect of aspirin consists in inhibiting the production of prostaglandins in damaged cells that send information to the brain through nerve fibres. In contrast, anticoagulant action is based on the dilution of blood, which is why people who take high doses of aspirin may have, for example, nosebleeds. Although it is a one‑component, simple drug, scientists are still finding new applications.

It is a reaction typical for a group of compounds containing in their structure a characteristic element - a phenolic group. In the case of poorly stored or expired medicines containing aspirin, this test allows to determine qualitatively the presence of undesired salicylic acid.

Antacids

Gastroenterologists (specialists in stomach and intestinal diseases) claim that about 5–7% of the population suffers from chronic stomach conditions, and at least 30–40% suffer from these symptoms once a month. People suffering from hyperacidity, associated with too aggressive action of hydrochloric acid on the stomach walls, use various types of neutralizing agents.

Neutralizing agents available in pharmacies contain salts or hydroxides of magnesium, calcium and aluminium. The basis of their action is the binding of hydrogen ions and increasing the pH in the stomach. This leads to partial neutralization of the acid gastric contents, as well as a partial reduction of pepsin (digestive enzyme) activity.

Task 1

Watch the movie explaining the effect of antacids.

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Animacja przedstawia neutralizowanie nadmiaru kwasu w żołądku. Głównym zadaniem żołądka jest trawienie. Proces ten odbywa się dzięki obecności w żołądku pepsyny oraz kwasu solnego. Gdy żołądek wydziela zbyt dużo kwasu solnego, to cierpimy na nadkwasotę. Objawom nadkwasoty działamy stosując leki neutralizujące nadmiar kwasu w żołądku. Działanie takich leków polega na zobojętnianiu kwasów zasadowymi składnikami leku.

Animacja przedstawia neutralizowanie nadmiaru kwasu w żołądku. Głównym zadaniem żołądka jest trawienie. Proces ten odbywa się dzięki obecności w żołądku pepsyny oraz kwasu solnego. Gdy żołądek wydziela zbyt dużo kwasu solnego, to cierpimy na nadkwasotę. Objawom nadkwasoty działamy stosując leki neutralizujące nadmiar kwasu w żołądku. Działanie takich leków polega na zobojętnianiu kwasów zasadowymi składnikami leku.

Film dostępny na portalu epodreczniki.pl

Animacja przedstawia neutralizowanie nadmiaru kwasu w żołądku. Głównym zadaniem żołądka jest trawienie. Proces ten odbywa się dzięki obecności w żołądku pepsyny oraz kwasu solnego. Gdy żołądek wydziela zbyt dużo kwasu solnego, to cierpimy na nadkwasotę. Objawom nadkwasoty działamy stosując leki neutralizujące nadmiar kwasu w żołądku. Działanie takich leków polega na zobojętnianiu kwasów zasadowymi składnikami leku.

The process that takes place in the stomach after taking neutralizing agents can be presented as the equation of neutralization reaction of base with an acid:

${\mathrm{H}}_3{\mathrm{O}}^{\mathrm{+}}+{\mathrm{OH}}^{-}\to 2{\mathrm{H}}_{\mathrm{2}}\mathrm{O}$

Gastric juice is secreted by the glands and epithelial cells of the gastric mucosa. During the day, the stomach secretes 2500–3000 cmIndeks górny 3³ of gastric juice with a pH of 1.0 to 1.5. Under physiological conditions, hydrochloric acid has a constant concentration, only its volume in the gastric juice changes. The main role of hydrochloric acid is acidification of gastric juice and facilitating the digestion of proteins and the elimination of bacteria that get into the stomach with food. Heartburn arise as a result of throwing acidic stomach contents into the oesophagus.

Another drug commonly used in the case of stomach conditions is active carbon, also known as therapeutic or activated carbon. The healing effect of this substance is related to its sorption properties. After administration, it has a strong anti‑diarrheal effect. It is used in cases of food poisoning and poisoning with certain drugs and chemical compounds. It is characterized by a large absorbing surface and binds substances that cause poisoning, e.g.: paracetamol, ibuprofen, barbiturates, alkaloids, heavy metal salts. After administration, it is not absorbed from the gastrointestinal tract and is excreted.

Antibiotics – fighting the cause, not only the effects of the disease

To inhibit the growth of microorganisms, especially pathogenic bacteria, medicine uses antibiotics. These are organic compounds with a complex chemical structure, produced from metabolites of mould and fungi. In this way, so‑called natural antibiotics are produced. The medical industry is focused on the production of semi‑synthetic antibiotics:

• more effective – stronger with wider range of activity,

• chemically more durable,

• more resistant to bacterial enzymes,

• often cheaper to produce than natural medicines.

Biotechnological methods are used in the production of many antibiotics. The first natural antibiotic was penicillin. It was obtained from mould (a kind of fungi – Penicillium, which appears, for example, in rotten bread, fruits.

Currently, the pharmaceutical industry produces hundreds of antibiotics. Some attack many types of bacteria, others act only against one or two types of bacteria (these are selective).

Antibiotics, as all medicines, should always be taken in the right amount and as directed by your doctor. This is especially important because, apart from killing or neutralizing pathogenic bacteria, these also destroy the bacteria of gastrointestinal tract necessary for human. Very often it causes inflammation of the mouth and mycosis and leads to the multiplication of antibiotic‑resistant strains, which can be a serious health risk. Frequent bacterial resistance to the drug is associated with irrational antibiotic therapy.

Summary

• Chemical substances may affect the human body and cause the desired effect as expected (drugs) or act adversely - toxic (poisons).

• This is primarily determined by the dose of the substance and the way it penetrates the body (through the skin, respiratory system or digestive system). When using medication, it is very important to follow the doctor's instructions – take the right doses of the medicine and administer it during a sufficiently long period.

Keywords

Dose, medicine

Glossary