Drug Information Q&A Q7. How do drugs work?
Answer
There are several mechanisms by which drugs work. Most drugs are transported with blood to the affected area, where they act on cells and biological substances related to the disease to stop the progression of the disease or alleviate symptoms.
Explanation
In the case of oral medicines, they pass through the esophagus to the stomach and eventually reach the small intestine, where they are absorbed. Once absorbed, the drug enters the blood vessels surrounding the small intestine, passes through the liver, and circulates in the bloodstream throughout the body (systemic circulation), reaching the affected area in about 15 to 30 minutes.
Once the drug reaches the affected area, it binds to "receptors," which are proteins on the surface of cells, and triggers a cellular response, which then manifests itself as an effect.
A single cell has a very large number of receptors, and the drug selects and binds to the necessary receptor from among them. Substances that bind to receptors and produce effects similar to those of neurotransmitters and hormones (activating cells) are called agonists (agonists/stimulants). On the other hand, a substance that binds to a receptor but does not produce an effect (does not activate the receptor) and inhibits the function of the neurotransmitter or hormone to which it is supposed to bind is called an antagonist (antagonist/blocking agent). For example, beta agonists (stimulants), which suppress bronchial asthma attacks, bind to beta2 receptors on sympathetic nerves and act on nerve cells as agonists, causing bronchi to dilate, thereby allowing air to pass more easily.
On the other hand, when histamine, a physiologically active substance, binds to H1 receptors, blood vessels dilate, causing allergic symptoms such as nasal discharge and sneezing, but antihistamines, as antagonists, occupy H1 receptors and interfere with histamine binding without causing histamine-like signal transmission, Allergic symptoms can be suppressed.
However, not all diseases can be cured immediately by simply taking a drug. Drugs help to cure diseases. Humans have the natural healing power (see Q8), which is the ability to heal illness and injury on their own. For example, cold remedies suppress symptoms such as sore throat and fever, but this does not mean that the cold is cured. While suppressing the various symptoms of a cold with medicines, the natural healing power of the body will cure the cold. If you rely too much on medicines and do not follow the three principles of health (exercise, diet, and sleep), you will not get the full effect of the medicines.
Chart/Column
Mechanism of action of drugs
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Agonist (agonist)
Binds to a receptor and causes a reaction similar to that of a chemical substance
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Antagonist (antagonist)
Binds to the receptor and blocks the action of the chemical or hormone to which it is supposed to bind.
7｜The flow of drugs
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Absorption
Drugs that enter the body by mouth are broken down in the stomach, and most of them are absorbed in the small intestine, where they are taken into the bloodstream and enter the portal vein (a vein connected to the liver).
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Metabolism
Drugs entering the liver through the portal vein are broken down and their toxicity is reduced.
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Distribution
After passing through the liver, the drug is transported by the blood throughout the body, arriving at the affected site and acting.
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Excretion
After acting as a drug, it passes through the kidneys and is excreted out of the body as urine, or is excreted from the liver in bile, in stools, sweat, or saliva.
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