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Drug Development > Clinical studies to measure Pharmacokinetics > Flashcards

Clinical studies to measure Pharmacokinetics Flashcards

1
Q

What is pharmacokinetics?

A

Movement of drugs within the body.

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2
Q

What is the relationship between PK and PD?

A 
PK : 
- Drug
- Concentration in Blood 
This links to PD: 
- Drug Receptor Interaction 
- Effect 
- Clinical Outcome
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3
Q

Why is PK necessary to study?

A

Ensures the best conditions of efficacy and safety is used.

Allows dosage and dosing schedule to be administered.

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4
Q

What is the importance of plasma concentration?

A

Important predictor of drug effect.

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5
Q

What are the key determinants of plasma concentration?

A

Absorption
Distribution
Metabolism
Excretion

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6
Q

How is clearance brought about?

A

Metabolism and Excretion added together.

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7
Q

During clinical trials, where is the PK information summarised?

A

In the Investigator Brochure (known as IB)

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8
Q

What is the physiology affected by pharmacokinetics?

A 
GI tract ( A and M )
Liver ( M and E ) 
Kidneys ( M and E) 
Blood / Blood Flow ( D )
Skin
Blood - Brain Barrier
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9
Q

What is the effect of ageing on the pharmacokinetics?

A
  • Decreased first pass metabolism / protein binding / hepatic and renal excretion.
  • Increase in volume of distribution.
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10
Q

What is the effect of intestinal disease on pharmacokinetics?

A

Impaired absorbance.

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11
Q

What is the effect of kidney function on pharmacokinetics?

A

Decrease in elimination and protein binding.

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12
Q

What is the effect of liver disease on pharmacokinetics?

A

Decrease in 1st pass metabolism and elimination.

Fluid retention too.

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13
Q

What is the effect of congestive heart failure?

A

Decrease in GI absorption.

Altered volume of distribution.

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14
Q

What is the speed of fate affected by?

A

Determined by distribution.

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15
Q

What is the rate and extent of distribution dependent on?

A 
Blood Flow
Diffusion (Lipid Solubility and Size)  
Active Transport
Plasma Protein (Mostly Albumin)
Tissue Binding
Disease.
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16
Q

What is the distribution of the plasma?

A

5% proportion of total body fluid.

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17
Q

What is the distribution of the interstitial fluid?

A

15% proportion of total body fluid.

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18
Q

What is the distribution of the intracellular fluid?

A

35% proportion of total body fluid.

19
Q

What is the distribution of the intracellular fat?

A

20% proportion of total body fluid.

20
Q

What is the aim of drug metabolism?

A

Decrease drug activity

Convert lipid soluble drugs to more polar / water soluble metabolites in order to be excreted in bile or urine.

21
Q

Why are lipid soluble drugs not easily cleared by the kidney?

A

Largely reabsorbed in the proximal tubule.

22
Q

Where does drug metabolism usually take place?

A

In the liver as Phase I and II reactions.

23
Q

What is metabolism Phase 1?

A

Phase One: Cytochrome P450 Enzymes are involved (IN THE LIVER).

  • Oxidation
  • Reduction
  • Hydrolysis
24
Q

What other enzymes are used in metabolism phase I?

A

Monoamine Oxidase

Alcohol Dehydrogenase

25
Q

What is metabolism Phase 2?

A

Further increases water solubility.

26
Q

What are the processes which occur in metabolism Phase 2?

A

Glucuronidation
Sulphation
Acetylation
Methylation

27
Q

Do only some drugs undergo Phase II metabolism?

A

Yes.

28
Q

What are the 3 main routes of excretion?

A

Renal (Kidney)
Biliary (Liver)
Sweat / Breath / Breast Milk

29
Q

Explain Renal Excretion.

A

Glomerulus : Glomerular Filtration
Proximal Tubule
Proximal and Distal Tubules.

30
Q

Explain Liver Excretion.

A

Involves active transport and secretion.
Conjugated compounds which are water soluble are excreted in the bile.
Bacteria hydrolyses the conjugated drug by glucuronidase.
Enters the ENTEROHEPATIC CIRCULATION.

31
Q

What are the plasma concentration parameters?

A

Descriptive Parameters = Cmax / Tmax / AUC / t1/2.

Conceptual Parameters = Clearance (CL) / Bioavailability (F) / Volume of Distribution (Vd).

32
Q

What is the significance of the area under the curve?

A

Signifies the total amount of drug exposed for the entire time course.

33
Q

What is the conceptual PK parameter?

A

Clearance = Bioavailability = Volume of distribution

34
Q

What are the factors which affect bioavailability?

A

Pharmaceutical Preparation
Physiochemical Interaction
Patient Factors
1st Metabolism

35
Q

What does Clearanc (CL) mean?

A

Volume of blood cleared of drug per unit time. (L/hr).

36
Q

What is the maximum clearance?

A

Maximum blood flow to that organ.

37
Q

How do you work the elimination rate?

A

clearance X plasma drug concentration

38
Q

What does the elimination rate equal?

A

Maintenance dose rate. (MDR)

39
Q

How do you work out the maintenance dose rate?

A

clearance X steady state plasma drug concentration

40
Q

How do you work out the volume of distribution?

A

Total amount of drug in the body = plasma concentration.

41
Q

What does the volume of distribution rely on?

A

Size of molecule
Plasma protein binding
Lipophilic

42
Q

What is a high volume of distribution?

A

Very lipophilic and very small sized molecules.

Achieves a steady state plasma drug concentration much MORE quickly.

43
Q

What is a low volume of distribution?

A

Not very lipophilic

Plasma protein binding and large molecules.

44
Q

What does t1/2 determine?

A

Duration of action after a single dosage.

In multiple dosages = Time take to reach steady state of drug concentration

Drug Development (13 decks)

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