User:Marsar39

=Drug Excretion=

Drug Excretion is the process in which the human body rids itself of foreign substances. The two main organs that excrete drugs are the kidneys and the liver.

Drug Intake
Drugs are foreign invaders to the human body. In order to excrete drugs the drugs need to be able to get through the body’s defense mechanisms. Before being excreted a drug needs to be able to get past the selectively permeable membrane of the skin, penetrate the skin, or survive the low pH levels (high acidity) of the stomach.

Skin
The human skin is a selectively permeable membrane, which can act as a passage for certain drugs into the body. This type of absorption is called dermal absorption (through the skin) and is made possible by diffusion and can be explained through Fick’s Law. Only certain chemicals have the ability to penetrate the skin; therefore, only certain drugs are capable of being delivered via a patch.

Injections
Injections deliver medicine directly into the bloodstream when taken in fatty tissue or muscle tissue.

Pills
Taking medicine in pill form, via the oral cavity, relies on the drugs ability to penetrate the tough and highly acidic lining of the stomach and/or the small intestine to get into the bloodstream.

The Liver
The liver, or the hepatobiliary system is one of the main ways in which drugs exit the body. Excreted into bile in the liver are compounds with high molecular weights that usually bind to plasma proteins. The reason to believe that the liver is a major source for the body’s excretion process is that the bile contains large amounts of xenobiotics. Xenobiotics are chemicals that do not naturally occur in the body. They include almost every type of drug, many physiological compounds as well as chemicals and toxins found naturally in the environment; this suggests that the liver is a main path of excretion since the body’s tendency is to rid itself of xenobiotics.

The Kidneys
The kidneys are the other main way in which drugs exit the body. The kidneys are the main excreting organs, excreting water-soluble matter. Compounds with predominantly low molecular weights, compounds that are hydrophilic, having the tendency to bind to water, are less likely to bind to proteins and are excreted into the urine by the kidneys. Most drug metabolites are polar compounds and cannot get back into the circulation of the body without specific reabsorption transporting mechanics, and are therefore excreted into the urine by the kidneys after the filtration process is complete.

As a person ages the ability to excrete drugs through the renal filtration process decreases.

Other Methods of Excretion
The kidneys, liver, and exhalation of volatile anesthetics are the main contributors to drug excretion but the body can rid itself of toxins and drugs in other ways as well. Excretion occurs through the intestines, the saliva, the sweat, the breast milk, and the lungs.

Open Scientific Research
In today’s society the use of medicinal drugs is highly accepted. There is virtually a drug for everything; however, the way these various drugs work is uncertain. Even more uncertain is the way in which the human body excretes these drugs. . Not enough scientific research has been completed yet, but studies continue to be done on rodents, especially rats since their genetic makeup is very similar to that of humans. This research indicates that the kidneys and liver are the two main organs that excrete drugs in humans.