Drug Interactions With Other Drugs & Activity Within the Body

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  • 0:03 Drug Effects Upon the Body
  • 0:32 Tolerance and Cross-Tolerance
  • 2:06 Increases and…
  • 4:16 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Drugs can affect your body in quite a few ways. You'll learn about how they affect you and how they interact with one another to affect you by learning about tolerance, cross-tolerance, the additive effect, synergism, potentiation, and antagonism.

Drug Effects Upon the Body

You know how sugar and coffee make you all hyper and energetic? That alcohol and flu medicine can make you drowsy? And how you shouldn't drink alcohol with some drugs because it may be dangerous?

Well, all of that happens because the chemicals in these things - be they natural or synthetic - interact with your body in a certain way or with other drugs that you're taking. There are many different specific terms for how drugs associate with our physiological mechanisms and what this ends up causing. So, let's go ahead and take a look at them.

Tolerance and Cross-Tolerance

If you once lived out in a peaceful and quiet countryside, only to have to move to a big city, a huge change would've been the noise pollution all around you: people screaming, cars honking, jets buzzing overhead. Those making such a switch would likely be tearing their hair out from the lack of sleep. But over time, they'll begin to tolerate the newfound noise, as their bodies get used to all of it.

We can also gain tolerance to a drug. Tolerance is the reduced sensitivity to a drug with a subsequent need for more of the drug in order to achieve a desired effect. Basically, after a long period of time of using or abusing a drug, your body simply learns to deal with it, and you'll need to take more of it to produce the effects you felt when you first used it.

Or, to put it another way, once you get used to the mundane city noise after moving from the countryside, you'll only be woken up by really loud noises since you've grown accustomed to all the other small stuff.

A similar term to tolerance is cross-tolerance, the reduced sensitivity to a substance's effects because of a developed tolerance to another similar drug.

It's kind of like saying that you no longer wake up to a truck's horn anymore because you've gotten used to not waking up to a car horn. They're kind of the same things, despite being just a bit different. But because you're tolerant to car horns you won't wake up to truck horns anymore, either.

Increases and Decreases in Drug Effects

Like cross-tolerance, there are more effects that can occur between drugs.

One of them is called the additive effect. In the additive effect, the combined effect produced by two or more drugs is equal to the sum of the effect of each drug given alone - meaning 1 + 1 = 2. Each drug's effect is simply added to the other to come up with a combined total effect.

In the additive effect, a combination of drugs does not produce an exaggerated combined effect, as it does in synergism. Synergism refers to an exaggerated effect caused by the use of two or more drugs that are similar in their action.

Another way of phrasing this is, the combined effect of two or more drugs is greater than the sum of the effects of each drug when they're given alone. Meaning, 1+1 doesn't equal 2 in this case. Instead, when synergistic drugs are given, 1 + 1 = 5.

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