Pharmokinetics / pharmacodynamics Flashcards by Alex Loftus

Partition coefficient (lipid/water)

dissolve drug in water, add equal volume fat, see where drug separates

[oil] / [water] = coefficient

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Aspirin ionization

Gets deionized in the stomach (carboxyl group)

Reionized in intestine, then can’t leave

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How long for a drug to be available all over the body once in the blood?

~120 sec

Mana said ‘within a minute’

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Pharmacodynamics

Study of biochemical and physical effects of drugs

binding to effector proteins

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What is depot binding?

When drugs bind to other proteins / tissues (e.g. fat, bone marrow, etc)

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If a drug binds to bone marrow, what happens in terms of concentration, etc?

Drug stays in the body longer

Less drug at the intended site of action

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How / where are most drugs inactivated?

The liver

Broken down / altered by enzymes

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Is glucose a drug?

No.

Drug = non-nutritive chemical that alters physiology

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If you alter the sympathetic nervous system but not the CNS with a chemical, is that a psychoactive drug?

No. Chemicals must get through the BBB and get into the CNS to be considered a drug.

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What is pharmacokinetics?

How drugs move around.

How they’re administered, where they go once you administer them, how they’re metabolized, how they leave the body

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pharmacokinetic binding

The exact way in which a drug attaches to a receptor, pump, enzyme, etc.

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How are drugs inactivated in metabolism?

increase polarity of drug so that it can’t go through stuff

Lots of other stuff

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What is the most common route of drug administration?

What are the advantages / disadvantages?

Oral: safe, don’t need help

Problems: all kinds of things can change how fast you absorb it. Hard to predict

First-pass metabolism

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What is the vomiting area of the medulla called?

How does it determine vomiting?

area postrema
Area in the medulla with no BBB
Samples blood to determine if you should throw up

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What are some other ways to get drugs in your body?

ICV (intraventricularly): directly into brain
IV (intravenous): into blood
IM (instramuscularly): Localized at injection site.

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How fast are the effects of inhalation?

Almost immediate - heavily vascularized, thin membranes in the lungs

Every molecule has the chance to go to brain before liver

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What is first-pass metabolism?

Drug gets metabolized in the liver for excretion before it does other stuff

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What is the ‘vehicle’ for a drug?

The medium through which it’s delivered

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Why is rectal administration useful?

Lower third of digestive system doesn’t suffer from first-pass problems (doesn’t pass through liver)

Huge absorptive surface there

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What is the route for first-pass metabolism?

Anything that goes through liver (up to 20-30% of drug inactivated before it gets to brain)

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How much total drug movement is there for aspirin in stomach vs. small intestine?

More in small intestine, BECAUSE of absorptive surface!

With same amount of absorptive surface, stomach would be better

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What does a drug need to get into the CNS?

Small, lipid-soluble, or transported

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What are platelets? What do they relate to?

Proteins found in blood

Depot binding - psychoactive drugs can bind to them instead of go into CNS

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What do liver enzymes do?

Break the drug down (change it structurally so that it can’t bind)

Normally make more water soluble

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What are metabolites? Active metabolites?

Products of a liver enzyme. Has been chemically changed somehow Active: Exert psychoactive effects after becoming metabolites

What happens in phase II metabolism?

You add stuff - change structure so that it can't bind to stuff. New functional groups

What happens in Phase I metabolism?

Oxidation / reduction Structure isn't changed though (as in, new functional groups don't get added)

Where are polar drug species excreted?

Urine ('renal elimination')

Where are nonpolar drug species excreted?

Feces ('biliary elimination')

What is cross-tolerance?

e.g. history of cigarette smoking causes ethanol tolerance The same enzyme metabolizes two drugs, so taking one drug helps with metabolism of the other

What is zero-order kinetics?

Rate of metabolism is constant / linear

What is first-order kinetics?

Rate of metabolism greater with more plasma levels - exponential decrease

What is the half-life?

Time it takes for drug to eliminate to 1/2 of its peak plasma level

What does the half-life look like with zero-order kinetics?

Half-life decreases with decreasing concentration

What does the half-life look like with first order kinetics?

Length of half-life is constant

Specific vs. nonspecific drug effects

Specific: effects based on interactions of a drug with target tissue Nonspecific: based on characteristics of the individual taking the drug, not on the drug's interactions with target tissue (e.g. mood at the time, diet, etc)

Example of nonspecific drug effect?

e.g. placebo

What are enteral methods of drug administration?

Use the gastrointestinal tract to get agents in the body

What kinds of enteral administration are there?

oral, through rectal cavities

What is the opposite of enteral administration?

parenteral e.g. injection, pulmonary, topical administration

topical administration

administration to body surface

What are four effects of depot binding?

- Drugs stay in tissue longer - Drugs that compete for depots could be displaced - onset of action could be delayed - Depots could be responsible for termination e.g they go to CNS first, but then depots change blood/brain concentration difference and cause them to leave cns faster

What are microsomal enzymes and where are they found?

Liver enzymes that metabolize psychoactive drugs Found in smooth ER of liver cells

What class of microsomal enzyme is responsible for metabolizing most psychoactive drugs?

Cytochrome P450 (CYP450)

What is Kd in relation to pharmacodynamics?

Affinity of drug for receptor. Kd = [drug][receptors] / [drug + receptors] Drug + target --> Drug-target complex

If you have a higher Kd, what happens to the drug's affinity for a receptor?

Drug has less affinity for receptor (higher concentration of drug/receptor individually)

What is the term for how well a ligand activates a receptor / produces a functional response?

intrinsic activity

What is the magnitude of a drug's effects called?

Potency

What makes a drug more potent?

affinity and intrinsic activity

What is an inverse agonist? How is it different than an antagonist?

An inverse agonist actively creates a negative response (has effects by itself) An antagonist simply prevents a positive response (can't have an effect by itself)

What is the drug dose generally described in terms of?

Weight of drug / weight of recipient | in a given volume of vehicle

What is the ED50 of a dose response curve?

The dose at which 50% of people taking the drug have the response that specific curve is measuring

What two things do you need on a good dose response curve?

One dose at 0, so you know where there's no effect A second dose past the asymptote, so that you know there is an asymptote

What is the therapeutic window for a drug defined as?

You're past the ED10 of the therapeutic effect You're before the ED10 of the toxic effect

What drugs make up the stimulants?

Amphetamine Cocaine Nicotine

What drugs make up the depressants?

Barbituates | Alcohol

What drugs make up the analgeisics?

Morphine | Codeins

What drugs make up the hallucinogens?

Mescaline LSD Psilocybin

What drugs make up the psychotherapeutics?

Prozac | Thorazine

Synergistic drug effects

Both drugs together cause a greater overall effect Additive effects or potentiation

Antagonistic drug effects

Both drugs together cause decreased effect

Drug code names

e.g. Ro 5-2807 ``` 5 = general structure Ro = company 2807 = iteration of it ```

decongestant

Shrink swollen blood vessels

What is a pharmacological activity classification?

Classify drugs according to primary pharmacological activity But there can be multiple effects

What effect of a compound is used mainly to classify them?

The compound's therapeutic use

Do you want a high or low TI?

High More TI = you can take more of the drug without worrying about a bad side effect Safer drug

What is TI?

Therapeutic index Ratio of LD50 to ED50 (lethal dose to effective dose)

What is oral administration?

Take by mouth

What is intravenous administration?

Put in veins (depleted O2)

What is intraperitoneal administration?

Put drugs into the body cavity

What is subcutaneous administration?

Put drugs directly under skin

What is intramuscular injection?

Into the muscles

Pharmokinetics / pharmacodynamics Flashcards

(72 cards)