What Is a Drug?

20.02.2021 |

Episode #1 of the course Introduction to drugs and behavior by Dr. Daniel McGrath


Welcome to the course! My name is Dr. Daniel McGrath, I am an Associate Professor of Psychology and I live in Canada. I have been teaching university psychology courses for the past ten years and I am excited to offer this course on Highbrow! I have also had the pleasure of teaching university courses on Drugs and Behavior. In this course, the primary goal is to provide you with an overview of how psychoactive drugs work and how they influence our behavior.

When you think about it, drugs play an important role in our lives. If we have a headache, most of us do not think twice about swallowing two acetaminophen tablets and maybe taking a nap. We rely on drugs as medication for almost any ailment you can think of. However, many drugs are also recreational. In this case, the psychoactive effects of a drug can be pleasurable instead of healing. This broad category of drugs will be the focus of this course.

We will start by discussing how drugs enter the body and then the brain. From there, we will cover what happens after repeated use of a drug, namely tolerance, withdrawal, and for some people, addiction. Lastly, the course will present some of the most commonly used psychoactive drugs in their own lectures.

So, what is a drug? The answer may seem obvious, but is it? A drug is an exogenous substance, meaning that it originates from outside the body. However, does that mean that all exogenous substances are drugs? Most people would likely say no, probably not. For example, a multi-vitamin is an exogenous substance, but it doesn’t quite qualify as a drug in the traditional sense. The definition of a drug also takes the intention of the user into account. For instance, if a person takes a substance with the intent of “getting high”, it is safer to say that the substance could be considered a drug.

For the purposes of this course, we will focus on psychoactive drugs. A psychoactive drug is a substance that directly leads to alterations in mood, perception, and other cognitive processes. There are numerous classes of psychoactive drugs ranging from stimulants such as cocaine to depressants like alcohol. Furthermore, many psychoactive drugs are illicit, in other words, illegal. For example, heroin, cocaine, and cannabis (in some countries/states) are illicit drugs. Yet, many psychoactive drugs are licit (legal) for adults in most countries, such as caffeine, alcohol, and tobacco. Additionally, as you will soon learn, there is a wide range of psychoactive effects, side effects, harms, and addiction potential across these drugs.

A major factor in how psychoactive drugs affect the user is how they took the drug in the first place. The route of administration is often key in how quickly a drug will impact behavior. Some drugs, such as cannabis, for example, have numerous routes of administration. Whereas others, like alcohol, have one primary route of administration. Some of the most common routes of administration include:

Inhalation: inhaling either gas or smoke directly into the lungs. Drug particles (e.g., nicotine) are diffused through lung tissue and into the blood

Intravenous: injecting a drug directly into a vein using a hypodermic needle and syringe

Intramuscular: injecting a drug into a large muscle with a hypodermic needle

Subcutaneous: injecting a drug just beneath the skin

Oral: a drug is swallowed, passes through the stomach, and is absorbed into the bloodstream while in the intestinal tract

Sublingual: a drug is placed under the tongue and absorbed into the blood through the mucous membrane

Buccal: a drug is placed between the gums and cheek and then absorbed into the blood

Intranasal: snorting a drug into the nostrils, which is then absorbed through the nasal mucosa

Transdermal and topical: absorption into the bloodstream through the skin using patches and creams

In terms of how quickly drugs can enter the bloodstream and then be carried on to the brain, some routes of administration are faster than others. In particular, intravenous administration (IV) is very fast. IV heroin use provides an intense high for the user as large amounts of the drug will quickly enter the brain. In comparison, drugs that are consumed orally take much more time to reach the brain. There are many factors involved in this process; we will discuss how drugs make their way to the brain in more detail in the next lecture.

See you tomorrow!


Recommended book

Never Enough: The Neuroscience and Experience of Addiction by Judith Grisel


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