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M&R > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

0
Q

What is pharmacodynamics?

A

Is the drug producing the desired effects?

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1
Q

What is the pharmacokinetics process?

A

Is the drug getting to the site of action?

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2
Q

What is the oral bioavailability of a drug?

A

The proportion of a drug given orally that reaches the circulation unchanged.

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3
Q

What does the amount of drug that reaches the circulation unchanged depend on? (If taken orally)

A

First pass metabolism and gut absorption.

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4
Q

What factors affect the rate at which a drug is absorbed when taken orally?

A

Pharmaceutical factors and gut absorption

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5
Q

Define sublingual

A

Medication taken under the tongue

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6
Q

How is first pass metabolism avoided?

A

Administered by different routes:

  • parenteral
  • rectal
  • sublingual
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7
Q

What is the volume of distribution?

A

The theoretical volume into which the drug is distributed if this occurred instantaneously.

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8
Q

How is the drug distribution worked out?

A

Extrapolating plasma levels to zero time

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9
Q

When are protein binding interactions important?

A

When the object drug is highly bound to albumin
When it has a small volume of distribution
When it has a low therapeutic ratio (therapeutic window is narrow)

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10
Q

What is significant about drugs binding to proteins?

A

Only the free drugs can be metabolised get to the target receptor

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11
Q

Tell me how object drugs and precipitant drugs work

A

Object drug is given at a lower dose than there are albumin binding sites.
Precipitant drug is given at a greater dose than the number of binding sites, displacing object drug.
Increases toxicity of object drug due to higher free levels

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12
Q

Give an example of an object drug and a precipitant drug

A

Warfarin and aspirin

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13
Q

What are first order kinetics?

A

Rate of elimination is proportional to the drug level.
A constant fraction of drug is eliminated per unit of time.
A half life can be determined.

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14
Q

What does a first order drug look like on a graph?

A

Curves downwards

Take the log of y against time and the line becomes linear.

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15
Q

What does a drug with zero order of kinetics look like on a graph?

A

Straight line

16
Q

When do all drugs become zero order?

A

At high doses.

17
Q

How long does it take for a steady state of drug concentration to be achieved?

A

5 half lives

Irrespective of dose or frequency of administration

18
Q

How is the loading dose determined?

A

By the volume of distribution.

19
Q

Significance of first and zero order kinetics?

A

First order - therapeutic response is predictable if the dose increases
Zero order - therapeutic response can suddenly escalate as elimination mechanisms saturate.

20
Q

When do drug interactions in metabolism matter clinically?

A

When they have a low therapeutic ratio

When the drug is being used at the minimum effective concentration When the drug metabolism follows zero order kinetics.

21
Q

Conditions for a drug to be reabsorbed from the renal tubule lumen?

A

Must be at its pI so it has no overall charge. Only then is it lipid soluble.

22
Q

Enteral ways of administering a drug?

A

Sublingual
Oral
Rectal

23
Q

Parenteral ways of taking a drug?

A 
Subcutaneous
Intramuscular
Intravenous
Inhalation
Transdermal
24
Q

How is the amount of oral bioavailability measured from a graph?

A

The area under the curve of blood drug level vs time

25
Q

How can the rate of bioavailabilty be measured from a graph?

A

The peak height and rate of rise of drug level in blood

Gradient?

26
Q

What is LD50?

A

Lethal dose in half of the population

27
Q

What is the ED50?

A

The effective dose in 50% of population

28
Q

Two examples of an object drug and precipitant drug

A

Warfarin and aspirin

Tolbutamide and sulphonamides

29
Q

What happens during phase I and phase II of drug metabolism?

A

I: oxidation, reduction, hydrolysis
II: conjugation

30
Q

What carries out phase I metabolism?

A

Mixed function oxidases in the liver including:
NADPH cytochrome P450 reductase
Cytochrome P450

31
Q

Features of phase I enzymes?

A

Low substrate specificity
Affinity for lipid soluble drugs
Enzymes are inducible and inhibitable

32
Q

Which is saturable, zero or first order elimination of drugs?

A

Zero

33
Q

What is the pharmaceutical process?

A

Is the drug getting to the patient

M&R (10 decks)

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