Pharmacology is defined as the scientific study of the actions of drugs and their effects on a living organism. It is the scientific study of drugs that includes their origin, actions, interactions and properties. There are two terms that we should know when we remember the term pharmacology which are; pharmacokinetics which is the effect of the body on the drug and pharmacodynamics which is the effect of the drug on the body. A substance abuse counselor should always have a great knowledge of pharmacology because without it a counselor may have difficulty understanding the very important factors that play a key role in understanding medications, such as side effects, potency, withdrawal and safety of the particular drug. Pharmacokinetics is an important term to know when dealing with drug administration and its effects. Pharmacokinetics is the branch of pharmacology that deals with what happens to drugs when they are ingested or administered. The effects of a substance are influenced by how the substance enters the body. There are many routes of administration, for example; a drug can be inhaled and absorbed into the lungs, taken orally, injected into a vein, into the muscles or under the skin, snorted through the nose or absorbed into the mucous membranes, drunk and absorbed from the small intestine or absorbed through the skin. Inhalation, drugs such as nicotine, solvents, marijuana and other drugs used for lung disorders are inhaled through the mouth. Some drugs such as cocaine are usually inhaled (snorted) through the nose where they are then absorbed through the mucous membranes of the nose. Injection is a way of introducing a drug (liquid) into the body using a needle and syringe, usually injecting... middle of paper... harmful consequences and neurochemical changes in the brain (roughly matches the definition of addiction of the DSM, but remember that the DSM uses the term addiction). Another definition of addiction is that it is the psychological and physical dependence on a substance. There are many different definitions of addition because the dependencies vary. For example, some treat addiction as a behavioral issue, so does that mean that addiction is only related to behavioral problems? It is logical to say that not all drugs are equally addictive, just like the effect of the drug itself. However, the potential for addiction has many interrelated factors, such as the ability of the substance to act in the pleasure center of the brain (site of addiction). Therefore the definition varies, as what defines a doctor, researcher etc. may vary in difference with the next scientist, etc..