How Does the Medicine You Take Find Its Way to the Painful Spot?

"How does a medicine taken by mouth know where it hurts and go there?"

This is one of the most frequent, and one of the best, questions I get in the consultation room. Medicine enters the stomach and circulates through the whole body on the blood. It goes to the tips of the toes and to the top of the head. So why does it act precisely at the painful spot?

I answer like this. It is not that the medicine finds the painful spot; it is that the painful spot catches hold of the medicine.

The painful spot is chemically different from its surroundings

Inflamed tissue is a completely different environment from the healthy tissue next to it. On the outside it is just a "painful spot," but inside, three things have changed.

First, it has tilted toward acidity. When inflammation arises, the cells in that area come to make energy in a state of oxygen shortage, and in that process acidic substances accumulate. The pH drops below that of the surroundings.

Second, the pressure has risen. It swells, fluid pools, and the tissue becomes taut. This pressure works the opposite way from what is commonly assumed — high pressure does not draw compounds in; it makes them harder to get in. What does get in, on the other hand, has trouble getting back out. It is a place where both the coming and the going grow slower.

Third, the blood vessels have loosened. In an inflamed area the vessel walls become slack, so substances leak out more easily. This is a device of the body for summoning immune cells to that spot.

So what happens?

The drug components circulating in the blood usually don't travel alone. They move bound to other substances, and the binding comes undone where the conditions are right.

Those conditions are exactly the ones above. They leak out where the vessels are loose, and the binding comes undone where things have tilted acidic. And at a spot where the pressure is high and drainage is slow, what got in stays a long time.

A drug component circulates through the whole body
        ↓
When it meets a spot with different pH · high pressure · loose vessels
        ↓
The binding comes undone and it leaks into the tissue and lingers
        ↓
Its action grows stronger at that spot

The components go everywhere in the body. It's just that a spot where the action stands out comes to exist separately.

This changes my practice

Once you accept this view, the goal of treatment changes.

The common approach asks "which component is good for pain." I ask one step earlier. "What kind of environment is this person's painful tissue in right now?"

• Is it a place where high pressure has blocked circulation?
• Is it a place where fluid has pooled and won't drain?
• Is it a place long hardened, where substances can't come and go?
• Is it a place where a low-grade inflammation has lingered without cooling?

Even the same lower-back pain, if this answer differs, the prescription differs. For some the direction is to drain what has pooled; for some, to soften what has hardened; for some, to cool an overheated nerve.

Before choosing the medicine, I first look at the conditions of the place the medicine will arrive at.

A story Korean medicine has told for a long time

Korean medicine has long used the words "a blocked spot," "a pooled spot," "a spot where heat has knotted." I do not read these words merely as metaphor.

• A blocked spot — tissue where circulation and material exchange are not occurring
• A pooled spot — tissue where fluid has stagnated and pressure has risen
• A spot where heat has knotted — tissue where inflammation persists and the chemical environment has changed

What people of old read with their fingertips and eyes, we can now say again in the language of pressure, acid-base balance, and vascular permeability. I believe this is not a way of belittling Korean medicine, but of clarifying what that observation was actually seeing.

Why I palpate the painful spot

This is also why, when I examine, I feel broadly around the painful spot as well.

Whether it is hard or soft, where the pressure pushes when I press, whether there is heat or, on the contrary, coldness. These are signals that tell me the environment the tissue is in. If imaging shows bone and structure, the hand reads the environment. So when a test is normal and yet there is pain, something remains that must be read by hand.

I did not want to answer "that is just how it works"

I did not want to answer the question "how does the medicine find its way to the painful spot" with "that's just how it works." What happens in the body has reasons, and knowing those reasons helps a great deal in carrying the treatment forward together.

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Written by Dr. Heo Ji-young (PhD in Korean Medicine Pathology, Kyung Hee University · former Research Professor of Herbology, Kyung Hee University)