Pharmacology/Overview of Pharmacology
Basics of Pharmacology
Understanding how the science of pharmacology works will help us understand questions like, "How come a person's stomach burns after taking an aspirin tablet?" Or even perhaps why some grapefruit juice can increase the blood levels of some medicines in people. Pharmacology deals with how medicine and their chemicals affect the body's reactions to them. Pharmacology is immensely important for treating diseases and how medicine affects the organs of the body. Pharmacology can allow one to examine how drugs in the organs of the human body affect them and how they stay in it. In addition, pharmacology deals with how medicines interact with cells and genes, which affects the function of the cells and the body.
Drugs in Pharmacology
When medicines reach the reacting spots in the body, many events and things occurs along the way when it reaches that spot. There are four basic stages of the life of medicine in the body. It is known as absorption, distribution, metabolism, and excretion. This entire process is known as ADME.
Absorption describes how when medicines enter the body they are are absorbed into the bloodstream from their administration point. There are a few ways to enter medicine in the body. One way is orally like swallowing a pill and another is intramuscular, meaning having a needle injected into your body. Another example is entering subcutaneously like injecting insulin right below the skin. One more example is transdermal like wearing a skin patch. A main obstacle a drug faces when entering the body is the absorption stage. Medicines that are ingested by the mouth are taken through a special blood vessel coming from the digestive tract to the liver, where significant amounts can be killed by metabolic enzymes known as the "first pass effect" Alternatives paths of entering drugs to the body go through he liver, which will go into the bloodstream directly or through the skin or lungs.
After the drug is absorbed the next step is known as distribution. This is when the bloodstream transports the medicine throughout the body. When this occurs, potential adverse reactions or side effects can happen when the drug interacts and affects another organ besides the organ that is originally targeted at. For example, a pain reliever used for the purpose of calming down a sore leg may result in irritating the stomach. This is a potential side effect. There are different factors that can affect the stage of distribution like if protein or fat molecules are in the blood. This is important because the protein and fat molecules can latch onto the drug molecules and essentially stop the progress of the drug. Drugs that are aimed at affecting the central nervous system like the brain and spinal cord have a huge obstacle. The immense obstacle for the medicine molecules is almost impossible to penetrate and the drug enters a barricade known as the blood-brain barrier. This barrier is designed from an extremely compact and tight woven mesh of capillaries packed together as a defence wall against harmful and deadly substances like poisons or viruses. However, pharmacology has developed ways to bypass this barrier.
The next step after distribution is metabolization. This is when the drug is broken down and it takes two steps most of the time. These steps occur mainly in the body's chemical processing plant known as the liver. The liver has many chaotic events and activity going on but it is very controlled activity. The things that are taken into the bloodstream regardless of how it was taken in in the first place, is transported to the this large internal organ. This is where the chemicals are rearranged to form new structures used for the body. This is known as biotransformations.
These biotransformations occur in the liver are done by the enzymes. For each of our cells, we have various enzymes, taken from hundreds of thousands. Each enzyme is designed specifically for a certain function. Some of these enzymes break down molecules. Others can connect smaller molecules to form longer chains. Drugs most of the time make it easier to get rid of the substance in urine. A majority of the products of the enzymes that break down are called metabolites, which are not as chemically active as the original molecule. This is how scientists refer to the liver as a detoxifying organ. Once in a while drug metabolites can have chemical activities of their own, which can be as potent as the original drug. When doctors prescribe these drugs, it is important to factor in these effects. After the liver enzymes are completed on the medicine, the now inactive drug goes trough the final stage of the body known as excretion. 
- Alison Davis(2011).. "NIGMS", p. 3-6.