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Pharmacokinetics > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

Why is it important to state “normal renal function” in a monograph?

A
  • Do not want to overdose the patient with decreased renal function
  • Kidney acts as a part of excretion; therefore, need to decrease dose if renal impaired
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2
Q

Most drugs act……

A

Systemically

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3
Q

For a systemic drug to have a therapeutic effect, it must reach _________ and be delivered to _________ which is known as __________.

A
  • Most drugs act systemically, which means the drug must gain access to systemic circulation (bloodstream) and be delivered by the blood to the site of action (biophase)
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4
Q

What are some forms of drug delivery for as an example osteoarthritis?

A

Oral, Intravenous, Intra-articular (delivers drug right to site of action)

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5
Q

Briefly describe the process of oral drug delivery

A
  • Drug needs to be liberatedby the GI tract
  • Drug must get absorped into the bloodstream
  • Drug delivered to site of action
  • Blood perfuses sites of metabolism and excretion (therefore drug is getting excreted as it reaches site of action)
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6
Q

Briefly describe how drugs work to produce a therapeutic effect?

A

Drugs work because sufficient drug concentrations exist at the pharmacological receptor (site of action) after dosing

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7
Q

What affects the drug concentration reaching the site of action?

A

1) Size of Dose
2) Frequency of Dosing
3) Pharmacokinetics (Absorption, Distribution, Elimination [Metabolism, Excretion])
4) Site of Action (where is the receptor site located and its principles) - Can the drug get there

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8
Q

Briefly describe how the factors influencing drug plasma concentration influence each other. (Hint: What are the factors that influence drug concentration)

A

Size and Frequency of Dosing —> PK –> Concentration at Site of Action –> Clinical Response

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9
Q

Pharmacokinetic information is….. data. Importance?

A

Population Based Data

  • A patient will never show PK characteristics to that of the monograph
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10
Q

Define a clinical relevant dose. Are all doses considered “clinically relevant”?

A

A clinically relevant dose is a dose of a drug that will result in plasma concentrations (exposures) that are within the therapeutic window

  • Not all doses produce clinically relevant exposures
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11
Q

Define PK (simple)

A
  • What the body does to the drug
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12
Q

Define therapeutic window

A
  • The range of concentrations that result in appropriate clinical outcomes
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13
Q

What is the goal of an empirical dosage regimen (DR)?

A
  • ATTAIN (first goal in some period of time) and MAINTAIN therapeutic drug concentrations (Cp, ther) to treat a condition effectively
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14
Q

What does Cp, ther mean?

A

The drug plasma concentration that results in a therapeutic effect

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15
Q

What assumption in regards to plasma concent and therapeutic effect is made in PK?

A
  • Plasma concentrations need to have a relationship with therapeutic effect (whether proprotional or not)
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16
Q

Describe the relationship between Cp, DR, and PK.

A

A drugs effect depends on Cp.
Cp is determined by DR and PK

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17
Q

On a plasma drug concentration vs time profile, what is the x-axis and y-axis?

A

x-axis - Time (hours)
y-axis - Plasma Drug concentrations (Cp)

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18
Q

On a plasma drug concentration vs time profile, describe the dosing regimen of a drug that requires numerous doses?

A
  • After each dose, the body is accumulating drug so plasma concentrations will slowly rise (potential for a dose to go into the therapeutic window; however, the plasma concentration will fall below the therapeutic window until the next dose)
  • May also require multiple doses until a therapeutic level is achieved
  • Dose until the pharmacological effect is continuous
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19
Q

What is the goal of DR?

A

ATTAIN and MAINTAIN therapeutic drug plasma concentrations (Cp, ther) to treat a condition effectively

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20
Q

What is Css, ave?

A

Css, ave –> Average steady state plasma concentration

21
Q

Define Steady State

A
  • a dynamic equilibrium in which drug plasma concentrations stay within the therapeutic window
22
Q

The clinical benefit of a drug is usually seen when plasma drug concentrations are within the…..

A

Therapeutic Window

23
Q

Define therapeutic window

A
  • the range of plasma concentrations (Cp) which produces desired clinical response in a patient (between MEC and MTC)
24
Q

Define MEC

A
  • the minimum plasma concentration of a drug needed to achieve sufficient drug concentration at the receptors to produce the desired pharmacologic response,
25
Q

Define MTC

A
  • the concentration at which a drug produces unwanted side effects
26
Q

Define Clinical Response

A
  • refers to the onset, intensity, and duration of effect
27
Q

Is the therapeutic window the same for all people?

A

No –> PK parameters are population based
Therefore, application to an individual is unknown

28
Q

What kind of therapeutic windows do most drugs have?

A
  • Wide therapeutic windows
29
Q

Define Onset

A
  • When Cp reaches TW (MEC)
30
Q

Define Duration

A
  • Length of time Cp stays within the TW
31
Q

Define intensity

A
  • the height of Cp within TW or toxic range
32
Q

Draw a plasma concnetration vs time graph. Label No effect, onset, duration, intensity, TW, MEC, MTC, Toxic, Sub-therapeutic.

A
  • See Slide 19
33
Q

Why can we get away with Empiric DR if everyone has a different TW?

A
  • Wide therapeutic windows allow us to dose a drug to attain and maintain a TW (that will work for most of the population)
34
Q

The clinical response (i.e. onset, duration, intensity of effect) relate to…..

A

PK descriptive parameters

35
Q

Tmax informs us about…..

A

Onset

36
Q

Cmax informs us about…..

A

Intensity

37
Q

Half-life informs us about……

A

Duration

38
Q

What happens if Tmax is small?

A

If Tmax is small, the onset of a drugs effect is faster

39
Q

What happens if Tmax is large?

A

If Tmax is large the onset of a drugs effect is slower

40
Q

What happens if Cmax is large?

A

If Cmax is large, the intensity of the drug is increased

41
Q

What happens if Cmax is small?

A

If Cmax is small, the intensity of a drug is decreased

42
Q

Is a large Cmax always desirable?

A

No - a large Cmax for an individual may result in drug plasma concentrations above the MTC which may lead to adverse effects occuring

43
Q

If a drugs half-life is large, what happens?

A
  • A large half-life would result in a longer duration of action
44
Q

If a drugs half-life was small, what happens?

A
  • A smaller half-life would result in a short duration of action
45
Q

Plasma Drug Concentration best relates to……

A
  • Clinical Response
46
Q

Describe the LADMER System

A
  • Dosage Regimen –> Liberation –> Stomach, small intestine –> Absorption into the Blood Stream
  • Css,ave <—> Distribution throughout the Body
  • Css, ave —> Includes Metabolism by Liver and Elimination from the body (Kidney)
  • Css, ave = Drug Concentration at site of action —> Leads to clinical response
47
Q

Define Kinetic Homogeneity

A
  • describes the predictable relationship between plasma drug concentration and concentration at the receptor site where a given drug produces its therapeutic effect
  • how the drug concentration changes in the blood is the same at the site of action
48
Q

Describe the general relationship between plasma concentration and tissue concentration?

A
  • Proportional
49
Q

What is the goal of dosing for therapeutic purposes?

A
  • Produce drug exposures that result in a clinically relevant drug response

Pharmacokinetics (2 decks)

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