Drug Clearance and Elimination Half-Life Flashcards

1
Q

What element in Pharmacokinetics is Elimination associated with?

A

-Excretion

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2
Q

What is drug Elimination/Excretion?

A

-Removal of the drug

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3
Q

What is drug Half Life?

A

-Is the time taken for half the quantity/concentration to reduce from its initial value

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4
Q

What is used to calculate a drug’s Steady State?

A

-Half-Life

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5
Q

What is Steady State?

A

where the rate of drug administration=elimination/output

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6
Q

What is the main organ that carries out drug elimination?

A
  • Kidney

- Via Renal Filtration

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7
Q

What is calculated to express drug clearance?

A

Clearance (CL) -volume of plasma cleared of a drug over a specified time period

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8
Q

Describe the effects of different drug concentrations

A

Low-Sub-Therapeutic Effects
Medium-Therapeutic Effect
High- More toxic-adverse drug reaction (too many toxic metabolites)

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9
Q

Does absorption and Elimination occur at the same time?

A
  • Yes

- Associated with Steady State (SS)

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10
Q

Why does a drug’s plasma concentration decrease after passing through the liver?

A

-Phase 1 and Phase 2 metabolism taken place

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11
Q

What is Total Clearance Tc?

A

-Describes Elimination route of a drug but by several routes NOT one

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12
Q

What is the Clearance Rate formula?

A

CL=Rate of Drug Elimination/ [Drug]plasma

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13
Q

What is First Order Kinetics?

A

-Reaction rate is directly proportionate to concentration of reactants (e.g drugs)

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14
Q

What is Zero Order Kinetics?

A

-Elimination rate has reached its Vmax-max reaction rate

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15
Q

How does the elimination rate reach its Vmax in Zero Order Kinetics

A
  • Elimination Mechanisms are now saturated (full)
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16
Q

What does the Michaelis-Menten Equation calculate?

A
  • Rate Equation (Re) in a reaction

- Shows Elimination rate

17
Q

Why is Clearance calculated in the Pharmaceutical Industries?

A
  • Helps calculate how to get Steady State

- Drug administration- elimination of drug

18
Q

What is Elimination Half-Life?

A
  • Amount of time it takes for the blood plasma concentration of the drug to decrease by half
  • Usually X5 Half-lives meet Steady State (SS)
19
Q

What x2 factors does Elimination Half Life rely on?

A

-CL and Vd

20
Q

How does CL effect Elimination Half Life?

A
  • CL Increases- Half life deceases because drug being eliminated faster
  • CL Decreases-Half-Life increases
21
Q

How does Vd effect Elimination half life?

A

Vd Increases- Half life increases as more spread out drug stays for longer
Vd Decreases-Half Life decreases

22
Q

What is the formula for calculating Half Life?

A

t1/2= 0.693 xVd

CL

23
Q

What factors can effect CL?

A
  • Types failure-cardiac, renal, hepatic-as metabolism here etc
  • P450 Enzyme System
24
Q

What is Hepatic Failure?

A
  • Liver failure

- Affects Phase 1 and 2 metabolism

25
Q

What can ageing affect?

A

-Volume Distribution