Does the medicine you take "know" how to cure you?

Eating a tablet of ibuprofen when you have a headache may reduce the pain quickly; eating a tablet of ibuprofen when you have a fever may decrease your body temperature quickly. Have you ever thought about how ibuprofen knows that you have headaches, fevers, not other ailments?

It seems that drugs can precisely judge our pain and quickly and effectively slow or cure it. In fact, this is not the case, and drugs do not "know" where they should go at all.

How does the drug work in the body?

Drugs in the form of capsules, tablets or liquids enter from the mouth, pass through the throat, along the esophagus, stomach, and reach the small intestine and large intestine. Drug will be absorbed by all parts it get through to varying degrees. Generally speaking, the small intestine is longer and has small intestinal villi on it, which has a strong absorption function. Therefore, the small intestine is the main place for drug absorption.

Drugs used to treat diarrhea or constipation look for a target receptor in the small intestine, and other drugs cross the intestine into the blood before they look for a target. Some drugs, such as blood thinners, target receptors in the blood, and most other drugs reach other parts of the body (such as the liver) with the blood.

The hepatic portal vein is a special "highway" that delivers drugs absorbed by the small intestine through the blood to the liver. The drug is further broken down in the liver into various drug components and released back into the blood. All organs and tissues are inseparable from the nutrients transported by the blood, and drugs reach anywhere in the human body, but this does not mean that they work.

The chemicals of most drugs can only attach to specific protein molecules in the body, which are called receptors. On the cell surface and inside, there are many different types of receptors, each of which has a different shape and functions like a lock that can be opened with a matching key.

During the systemic circulation of drugs, they bind to appropriate receptors and perform specific functions. Painkillers perform the function of cutting off pain signals from the nerves; drugs prevent gastric acid secretion; antidepressants adjust chemicals in the brain; and antibiotics kill bacteria. In conclusion, there are many ways for drugs to produce effects, and the first thing to do is to grasp the target receptor.

How do side effects occur?

Ibuprofen can reduce pain and also reduce fever. Ibuprofen inhibits the synthesis of prostaglandins and prostacyclin, chemicals that cause inflammation and pain, when they bind to their receptors. When ibuprofen acts locally on inflammatory tissues, it reduces the synthesis of prostaglandins or other transmitters through the inhibition of enzyme activity, thereby reducing nerve conduction locally in the tissue and relieving local pain.

Prostaglandins themselves cause redness, swelling, pain, and fever, and when prostaglandins are reduced, they also play a role in cooling and reducing fever. Only when ibuprofen binds to the corresponding enzymes in the affected area can the drug work and eventually achieve the desired effect. If the drug does not bind to the target receptor, it will not produce the desired effect.

The mechanism by which drugs act is not foolproof, and drugs may also bind to receptors other than the target receptor, especially when the shape of the receptor is similar. When the drug binds to the wrong target, it triggers a series of chain reactions, which are the side effects of the drug. Therefore, we must take the medication at the prescribed dose.

If the dose is lower than the prescribed dose, the drug may not be able to bind to the target receptor and exert its effect. In contrast, when the prescribed dose is exceeded, the drug not only binds to the target receptor, but also causes unexpected reactions, that is, increases the probability of side effects. Each drug has a relatively certain list of side effects, such as causing stomach discomfort, drowsiness, dry mouth, etc., which will be indicated in the instructions.

For chemotherapeutic agents, side effects are inevitable. Chemotherapeutic agents are specifically designed for rapidly growing cancer cells. They may also attack other rapidly dividing cells (such as hair cells) while eliminating cancer cells, which is why chemotherapy always leads to hair loss.

R & D of smart drugs

To make drugs safer and more effective, researchers are working on the development of "smart drugs" that can precisely deliver drugs to target locations or activate the release of drugs through external stimuli. Ideally, drugs remain inactive near the target until they are activated.

Since the drug is excreted after it is removed from the target receptor, the patient needs to take the drug regularly. By controlling the activation of the drug, researchers can continuously maintain the drug at the dose level required in the body, thereby avoiding frequent medication.

In a recent study, researchers detected chemical signals that initiate drug release in vivo, forming a fully automated drug delivery system that efficiently and specifically delivers the correct dose at the right time, anywhere in the body.

In another study, researchers looked at microchips placed in the skin, spinal cord, or brain to deliver the drug precisely. This microchip has some holes that are loaded with drugs (such as chemotherapy or analgesic drugs) and covers the holes with gold foil. Applying a certain voltage to dissolve the gold foil cover, the drug is released.

Perhaps in the future, the smart drugs we take will not hover in the blood aimlessly, but the more realistic question is whether scientists can make "smart drugs" as cheap as traditional drugs.

Collected by Creative Biostructure Drug Discovery, whose mission is to accelerate the preclinical development of innovative drugs through structural insight.

Randi Warren from Creative Biostructure.