Pharmacodynamics

Question 1

What do we refer to when we talk about a drug’s half life?

Answer 1

We are talking about the time it takes from the peak concentration of a drug to reduce to half the concentration of the peak

Question 2

What is the corresponding metabolic rate when a half life is large? What about when it is small?

Answer 2

A long half life means that the drug is slowly metabolized, and the inverse is true if the half life is short

Question 3

What is the solution to get around metabolic breakdown when we want a drug to be in our system for a long period of time (for example, to treat depression)?

Answer 3

The solution is to attain a steady state plasma level

- take doses at shorter intervals to ensure that the drug never reaches the floor

Question 4

What is a steady state plasma level?

Answer 4

The calculation of how much and how frequently you have to take a drug to reach a steady state

Question 5

What is the goal of a drug regimen?

Answer 5

To achieve a steady state long enough for the drug to have its desired effect

Question 6

What are the 2 mechanisms for drug tolerance?

Answer 6

1. pharmacokinetic tolerance

2. pharmacodynamic tolerance

Question 7

Describe pharmacokinetic tolerance

Answer 7

In this process, there is a change in the number of enzymes to metabolize the drug (the body becomes more efficient at flushing out the drug)

Question 8

What is tolerance?

Answer 8

With prolonged exposure, the drug has a lesser effect

Question 9

What is induction?

Answer 9

An increase in the number of enzymes because of repeated exposure to the drug (happens over days)

Question 10

What is cross-induction?

Answer 10

Certain drugs can interact (thus, their enzymes are shared)

Question 11

What is an example of cross-induction?

Answer 11

You shouldn’t consume grapefruits when taking certain blood pressure medication, because the P450 enzymes are busy breaking down the grapefruit, and thus cannot effectively break down the drug

Question 12

What does pharmacokinetics help us determine?

Answer 12

A drug’s availability

Question 13

What does pharmacodynamics help us to understand?

Answer 13

Affinity and efficacy (which is the science of drug actions)

Question 14

What are the two components of a drug’s affinity?

Answer 14

1. dose-response relationships

2. receptor-ligand interactions

Question 15

What is a ligand?

Answer 15

Any substance that bonds to a receptor (either a drug or a neurotransmitter)

Question 16

What are some weak bonds?

Answer 16

1. ionic bonds
2. hydrogen bonds
3. vanderwaals

Question 17

What are some strong bonds?

Answer 17

bonds like covalent bonds (the old antipsychotic Haloperidol forms a covalent bond with a D2 receptor)
- once a covalent bond is made, it is very difficult to break, so the receptor might not be able to be used anymore = damages the brain

Question 18

What kind of bond do ligands generally have?

Answer 18

weak bonds

Question 19

If a drug’s affinity is high, and the drug is highly selective, what kind of dose would the person need?

Answer 19

A low dose

Question 20

If a drug’s affinity is high, and the drug is not highly selective, what kind of dose would the person need?

Answer 20

A higher dose

Question 21

What is one way we can think of drug affinity?

Answer 21

It is the probability that a ligand will bond to receptor (how much bonded/how much unbonded)

Question 22

What happens if we increase the amount of drug molecules in the brain?

Answer 22

It increases the probability of a drug bonding, so does increasing a drug’s affinity

Question 23

What is the law of mass action?

Answer 23

A formula that states:

drug dose + concentration of receptors = the amount of drug that is bound to a receptor

Question 24

What is kD?

Answer 24

The dissociation constant; represents how quickly a drug dissociates
- a low kD = a high affinity

Question 25

How can we measure drug affinity (exam question)?

Answer 25

We subtract nonspecific binding from total amount of binding

Question 26

What is Bmax?

Answer 26

The maximum amount of binding a drug can have

Question 27

What is affinity?

Answer 27

The bond between a drug and its receptor

Question 28

What is selectivity?

Answer 28

Choosing which receptors the drug should bind to