Intro/Drugs & Behavior

What is a drug?

• Chemical Substance

• Taken into the Body (administered)

• Alters Physiological Function

• Excluding Necessary Nutrients (not a nutrient)

• Intended to be Taken

Instrumental vs. Recreational Use

• Instrumental Use

– The user has a specific behavior goal in mind (sleep, wake, lower blood pressure)

• Recreational Use

– The user wants to achieve a pleasurable or psychological state (Tobacco and Alcohol) or wants to achieve a different state of mind

Drugs & Behavior

Drugs

• Drug use in society today is a SERIOUS problem

  • Driven by money

• Why is drug use viewed as a serious problem?

– Toxicity of the drug (damage or adverse effect of the drug)

– Potential for behavioral dependence

– Connection between drug use and crime/violence

Drug Toxicity

• The physical and psychological harm that a drug might present to the user in the short period after ingestion (Acute Toxicity) - a few hours or a couple of days = a short period

• Dose-Response Curve: the more an individual takes the greater the response

  • It is common to see an overlap between the ED and LD curve

  • Y-axis - the percentage of people that will have the set response (at 6 dose/pills 100% response)

  • ED = effective dose

  • LD = lethal dose

Dose-Response Curve

• Effective Dose 50 (ED50)

– Drug dosage for effective response in 50% of the sample

• Effective Dose 99 (ED99)

– Drug dosage for effective response in 99% of the sample

• Lethal Dose 50 (LD50)

– Drug dosage for lethal response in 50% of the sample

• Lethal Dose 99 (LD99)

– Drug dosage for lethal response in 99% of the sample

  • Drug B is most common for OTC medications

  • Drug C is the most lethal because the curves overlap too much

Therapeutic Index

• Determine the ratio of lethal dose to effective dose. It suggests drug’s toxicity

• Therapeutic Index = LD50/ED50

  • The dose needed to reach ED50 should be lower than the dose for LD50

  • The numerator (LD) should be greater than the denominator

  • The lower the index or margin of safety the more toxic it is

  • A therapeutic index of 1.7 vs 102 vs 53 - 102 is the safest medication

• The amount found to incur a 50% chance of dying relative to the amount effective for half of the population.(assumes half of the population dies)

• THIS IS TOO HIGH OF A CHANCE FOR DEATH!!!

Margin of Safety

• Margin of Safety = LD1/ED99

• The amount that would be effective for 99% of the population to incur a 1% chance of dying.

  • Drug B would be 5 / 6 (LD1 = 5 & ED99 = 6)

• These ratios are easier to calculate for prescription drugs than street drugs.

  • Can be lower than 1 and still be safe

  • The ED99 is usually the dosage prescribed

Drug Tolerance

• Ability of the drug dose to gradually diminish its effect on the user as the drug is taken repeatedly (caffeine, nicotine, etc.).

• Problem? - Increased dose vs. Lethal dose

• Also - what one person takes compared to a nonuser can have very different effects.

• Therefore, the number of times a person regularly takes the drug impacts tolerance.

• Behavioral Tolerance: The environment the user is in can impact tolerance.

  • At a party vs. study environment

• Metabolic Tolerance: over time the liver can increase the breakdown of a drug if taken regularly.

  • The body adapts to caffeine or drug breakdown and does it quicker

• Cellular Tolerance: Receptors will up-regulate (increase receptor #) or down-regulate (decrease receptor #) if too little or too much drug is taken over time.

Drug Dependence

• Physical Dependence: Person develops physical symptoms during withdrawal from drug.

• Drug has become normal part of physiological environment.

• These withdrawal symptoms are typically opposite of drug’s effects.

  • Taking blood pressure medication that decreases BP, and when taken off, blood pressure may increase (rebound hypertension)

• Psychological Dependence - Person attempts to avoid the withdrawal difficulties and feed the craving, or desire, for the drug.

• Substance Dependence: Person with significant signs of a dependent relationship

upon a drug.

• Substance Abuse: Person who continues to take a drug even when the drug (or drug- taking behavior) is creating specific problems for the user. Creating a physical and/or psychological problem.