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PHRM2500 > WEEK 1 > Flashcards

WEEK 1 Flashcards

1
Q

Pharmacokinetics and pharmacodynamics are two branches of a larger field of science called…

A

Clinical pharmacology.

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2
Q

T. or F.
Pharmacokinetics is the study of the effects of the drug on the body.

A

False. That’s Pharmacodynamics.

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3
Q

T. or F.
Pharmacokinetics is the study of the effect the body has on the drug.

A

True.

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4
Q

Pharmacokinetic processes can be broadly defined in terms of what acronym?

A

ADME. Absorption, distribution, metabolism, excretion.

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5
Q

The study of the time course of drug absorption, distribution, metabolism and excretion is called

A

Pharmacokinetics

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6
Q

Plasma drug concentrations (or sometimes blood or serum concentrations) are used as a
proxy measurement for the drug concentration at…

A

its site of action.

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7
Q

In a situation involving passive diffusion the driving force for drug movement is…

A

Drug concentration.

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8
Q

Most drug movement across biological membranes in the body is via…

A

passive diffusion.

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9
Q

T or F
The higher the drug concentration the faster the rate of drug movement.

A

T

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10
Q

T or F
Concentration-dependant movement is called a first-order processes.

A

T

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11
Q

T or F
If movement is inactive, it is concentration-independent

A

F

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12
Q

If drug movement involves an active process, then it is said to be a …-order process.

A

zero-order

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13
Q

T or F
During a first-order elimination process drug elimination is SLOWER at higher drug amounts
(or drug concentrations) and becomes FASTER as the drug amount (or concentration) drops.

A

False. Vice versa. RAPID, SLOWER

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14
Q

A first-order process can also be called a…

A

concentration-dependent process

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15
Q

A constant slope (a straight line) means that the rate of elimination is INDEPENDENT OR DEPENDENT of the amount of drug in the body.

A

INDEPENDENT

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16
Q

If a drug is being eliminated by zero-order elimination a INCONSISTENT OR CONSTANT amount of drug is
eliminated per unit time.

A

CONSTANT

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17
Q

T or F
Since we cannot practically measure drug concentrations in specific tissues, we measure it in the plasma and assume that this concentration is the SAME as that in tissue.

A

F
The plasma drug concentration is not the same as that in the tissue but rather it is RELATED to the tissue concentration. Plasma drug concentrations are commonly used because blood, being readily accessible via venepuncture is the body fluid most often collected for drug measurement.

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18
Q

T or F
When the drug has been metabolised, the parent drug has been cleared or eliminated, even though the metabolite may still be in the body.

A

T

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19
Q

T or F
The slope of the tangent to the curve is not equal to the rate of elimination of the drug.

A

False.
It is equal

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20
Q

T or F
The rate of elimination and the elimination rate constant are two different parameters.

A

T

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21
Q

What is the key difference between the elimination rate constant and the rate of elimination?

A

the elimination rate constant is a constant. Where as the rate of elimination is not a constant. The rate of elimination varies with
the amount of drug in the body.

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22
Q

T or F
The only time we know the amount of drug in the body is straight after an intravenous bolus dose.

A

T
at this time-point the amount of drug in the body is the dose we gave.

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23
Q

The rate at which a drug can be eliminated from the body in a first-order system depends
on…in the body and drug clearance in a given individual.

A

the concentration of drug

24
Q

What does MDR stand for in the context of drug clearance?

A

Maintenance Dose Rate

25
Q

For any drug dosed to steady-state the only pharmacokinetic parameter that describes
the relationship between drug dose rate and average plasma concentration is…

A

Clearance

26
Q

What is a Maintenance Dose Rate?

A

The Maintenance Dose Rate is the rate at which a drug needs to given in order to achieve a particular average steady-state concentration (combating clearance).

27
Q

You can calculate the maintenance
dose rate of a drug if you know what two things?

A

The drug clearance and the average
steady-state concentration you would like to achieve.

28
Q

T or F
It is possible to clear a portion of blood completely of drug.

A

False. It is impossible

29
Q

T or F
An extraction ratio can range from zero (no drug at all is extracted) to ten (all
the drug entering the liver is extracted in one pass of blood through that organ).

A

F
An extraction ratio can range from zero (no drug at all is extracted) to ONE (all
the drug entering the liver is extracted in one pass of blood through that organ).

30
Q

What is an extraction ratio?

A

The fraction of drug that is removed from a single pass of blood through an organ (e.g. liver).

31
Q

What does an extraction ratio tell us?

A

Extraction tells us about the intrinsic ability of the organ to eliminate the drug.

32
Q

The 3 major factors influencing hepatic clearance are…

A
  1. Liver perfusion (reflects drug delivery to the liver)
  2. The fraction of drug in the blood that is free or not bound to plasma proteins or blood cells
    and capable of interacting with hepatic enzymes.
  3. The intrinsic ability of the hepatic enzymes to metabolise the drug, (aka intrinsic clearance)
33
Q

We call the fraction of drug in blood that is not bound to plasma proteins or blood cells the…

A

free fraction.

34
Q

What is meant by the phrase “the intrinsic clearance of the liver”?

A

The intrinsic clearance is the intrinsic ability of the liver to remove (metabolise) drug in the
absence of restrictions imposed on drug delivery to the liver cells by blood flow and or binding
of the drug.

35
Q

What is Vmax?

A

Vmax is the maximum velocity at which a enzymatic reaction can occur at saturating substrate
concentrations (the maximum rate at which the enzyme can convert the drug to a metabolite).

36
Q

What is Km?

A

Km is the Michaelis constant, it is the substrate concentration at which the reaction rate is half of Vmax. It expresses how tightly the enzyme binds the drug substrate.

37
Q

T or F
hepatic clearance cannot be higher than hepatic blood flow.

A

T

38
Q

For drugs with low hepatic clearance, what are two key determinates of their clearance?

A
  1. The fraction of unbound drug, or how tightly the drug is bound to plasma proteins.
  2. How good the organ is at eliminating that drug.
39
Q

T or F
For drugs with low hepatic clearance alterations in liver blood flow make very little difference to the drug’s clearance.

A

T

40
Q

T or F
For drugs with a very high hepatic clearance the liver enzymes have very low activity towards the drug.

A

F
Liver enzymes have very HIGH activity towards the drug.

41
Q

T or F
For a low clearance drug, the least important parameter is
how good the organ is at removing the drug (blood flow to the liver is less important).

A

F
It is the MOST important parameter

42
Q

T or F
For high-clearance drugs, the most important parameter is liver blood flow.

A

T
Because the faster you deliver
the drug to the liver the faster it will be eliminated.

43
Q

T or F
Any pathology that reduces organ perfusion (eg. heart failure) will reduce clearance.

A

T

44
Q

T or F
Any pathology that reduces organ function (eg. due to acute tubular necrosis) will increase clearance.

A

F
It will REDUCE clearance.

45
Q

T or F
Most organ systems in the body run in parallel.

A

T

46
Q

T or F
Creatinine clearance
provides useful information about the renal clearance of many drugs.

A

T

47
Q

For high hepatic clearance and high hepatic extraction ratio drugs, the primary determinant of variability in hepatic drug clearance is?

A

Hepatic blood flow.

48
Q

T or F
Total systemic clearance is the multiplication of the different clearance processes occurring for a given drug.

A

F
Total systemic clearance is the SUM of the different clearance processes occurring for a given drug.

49
Q

What does the AUC (Area under the concentration-time curve) tell us?

A

The AUC tells us about the exposure of the body to the drug. It s a measure of drug concentration over a time interval. It is really how much drug the body sees.

50
Q

T or F
The elimination rate constant (k) is the most important pharmacokinetic parameter.

A

F
Clearance (CL) rate is

51
Q

What are some factors that may affect clearance of a drug from the body?

A

Liver function, kidney function, body weight, cardiac output, drug-drug interactions, extraction ratio, genetics, plasma protein binding

52
Q

In patients with impaired liver function their drug dose should be increased/decreased to achieve the same level of drug exposure as people with normal renal function.

A

Decreased

53
Q

In patients with reduced renal function their drug dose should be increased/decreased to achieve the same level of drug exposure as people with normal renal function.

A

Decreased

54
Q

Pharmacodynamics describes the relationship between…

A

The unbound drug concentration at the receptor and the drug response (ultimately the therapeutic effect). aka concentration-effect relationship

55
Q

Pharmacokinetics describes the relationship between…

A

The dose and the unbound drug concentration at the site of action (a drug receptor), and the time course of drug concentration in the body. aka Time course of drug concentration in the body.

56
Q

T or F
When a drug has been metabolised, the parent drug has been cleared/eliminated

A

T
even though the metabolite may still be in the body.

57
Q

Uptake of a drug into tissues is not clearance if…

A

the unchanged drug eventually comes back out of the tissue, however this slowly occurs.

PHRM2500 (5 decks)

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