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Drugs: An Overview

What is a drug?
A drug is any substance that changes a person’s mental state or how their body functions; a toxin is a poisonous substance capable of causing death. The difference between the two can be small, and may depend on how much is taken. Drugs that affect how the brain works are called psychoactive; these include many legal and illegal substances.

What affects a drug experience?
Many of these factors need to be considered before taking any drug:

  • Purity (grade);
  • Dose (how much you take);
  • Setting (your environment and who you’re with);
  • Mental (state of mind);
  • Tolerance (the need to take increasing amounts to achieve the same effect);
  • Individual factors (including medications, immune system differences, sleep, gender); and
  • Entry (how the drug gets into your body).

If you’re taking multiple drugs (legal or illegal) at the same time, one drug can increase or decrease the impact of the other. This is especially important to know if you’re taking medications, since dosages are given for particular reasons. Your doctor considers all factors above when prescribing; with illegal drugs, or prescription drugs that aren’t yours, it’s impossible to predict which drugs will play off each other, or even possibly cancel each other out.

How drugs get into the body
A drug’s effect largely depends on how it’s administered. Intravenous injection and inhalation are the fastest ways to get a drug into the body; ingestion is the slowest. Injected drugs enter the bloodstream directly, hitting the brain within seconds; inhaled drugs get to the bloodstream through the lungs. A drug that’s ingested must travel from the stomach to the small intestines before reaching the bloodstream. Drugs may enter the body through mucous membranes in places like the nose, mouth or rectum; blood vessels here allow certain drugs to enter the bloodstream. Some drugs, like those in nicotine or birth control patches, are absorbed through the skin.

How drugs get out of the body
Some drugs, like inhalants, can leave the body through the lungs; others leave through the intestines. Most drugs are broken down by the liver and kidneys, and are excreted in urine. The effects of the drug depend on how fast the liver can break it down. Your liver can only process one drug at a time, so as one is being metabolized, the other is circulating in your body.

What the words mean
Some words come up often when talking about drugs. Short-term effects are what can happen when a person is on a drug. Long-term effects are those that can happen when a drug has been used for a prolonged period of time. A person is dependent on a drug if he or she has trouble controlling its use and needs to take it to feel ‘normal.’ A dependent person will experience withdrawal when drug use is stopped; withdrawal is the body’s inability to function normally unless the drug is present.

Learn more...

For More Information

The Center for Health Promotion at UHS offers information, interventions and referrals; call (413) 577-5181.

The Massachusetts Department of Public Health maintains a Substance Abuse Information and Education Helpline.
Call 1-800-327-5050, or go to