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Biomedical Pharmacology > Lecture 4 - Metabolism And excretion > Flashcards

Lecture 4 - Metabolism And excretion Flashcards

1
Q

What happens to most drugs in the body?

A

Bio transformation

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2
Q

What are the sites of metabolism in the body?

A

Liver (major site) Kidney Lungs Skin Intestine

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3
Q

What is the major site of metabolism in the body?

A

Liver

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4
Q

What is the effect of first pass metabolism on bioavailability?

A

Reduces?

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5
Q

What is the aim of the process of metabolism?

A

To change a drug into more water soluble molecules

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6
Q

What is the effect of metabolism of absorption?

A

Lowers

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7
Q

What is the effect of metabolism on excretion in urine?

A

Aids excretion

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8
Q

What is the effect of metabolism on polarity ?

A

Increases

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9
Q

What is the term given to drugs activated by metabolism?

A

Pro drugs

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10
Q

what are pro drugs?

A

Drugs activated by metabolism

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11
Q

In what form are pro drugs administered?

A

Inactive

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12
Q

Metabolism can produce more active metabolites which contribute to the action of drug. When can this occur?

A

when there is more than one step in breakdown e.g. benzo

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13
Q

What does metabolism often consist of?

A

Phase I and phase II

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14
Q

What is phase I metabolism?

A

A group of reactions which make an intermediate more active, increasing the ease of making something more water soluble for excretion

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15
Q

What is phase II metabolism?

A

Makes drug more water soluble

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16
Q

What Catalyses phase I reactions?

A

Enzymes

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17
Q

What is the most important enzyme that catalyses phase I reactions?

A

Microtonal mixed function oxidase

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18
Q

Where does microtonal mixed function oxidase reside?

A

Smooth endoplasmic reticulum of the liver

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19
Q

What does microtonal mixed function oxidase require to catalyse phase I reactions?

A

NADPH and molecular oxygen

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20
Q

What is the most important microtonal mixed function oxidase?

A

Cytochrome P450

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21
Q

What type of protein is cytochrome p450?

A

Haem

22
Q

What are human CYP isoforms?

A

Substrates for inhibition

23
Q

What is the most abundant human CYP isoforms?

A

3A4

24
Q

Where do phase II reaction mainly occur?

A

Liver

25
Q

What are phase II reactions?

A

Conjugation reactions which occur at polar groups

26
Q

Are conjugated products very water soluble?

A

Yes

27
Q

How are conjugated products excreted?

A

Water and bile

28
Q

what is the main phase II reaction?

A

Glucuronidation

29
Q

What is Glucuronidation?

A

Commonest conjugation reaction Endogenous reactant, UDP glucoronic six attaches to N, O or S atoms

30
Q

Effect of Paracetamol OD?

A

Liver damage Necrosis

31
Q

What are phase II reactions for paracetamol?

A

Sulphate conjugation, and glucuronide conjugation

32
Q

Phase I reactions for paracetamol

A

Cytochrome P450

33
Q

What percentage of paracetamol occurs by conjugation?

A

90%

34
Q

How Does the remainder of paracetamol metabolism occur?

A

Remainder metabolised by oxidation to produce toxic metabolite

35
Q

What isoform is crucial in paracetamol metabolism?

A

CYP2E1 isoform

36
Q

What happens to conjugation in response to overdosing?

A

Conjugation steps are saturated and cofactors are depleted Larger % of toxic metabolite produced Usually enough to deplete all available glutathione

37
Q

Where does excretion of drugs mainly occur?

A

Kidney

38
Q

What if clearance a measure of?

A

Elimination

39
Q

What is the rate of elimination dependent on?

A

Metabolism and Excretion

40
Q

How do you calculate clearance?

A

Rate of elimination/ plasma concentration

41
Q

How can renal clearance, as a measure of elongation be defined?

A

The volume of plasma cleared of drug by the kidney per unit time (ml/min)

42
Q

If a drug has a clearance of 10mp/non, how long will it take to clear 1 litre of plasma?

A

100 Mins

43
Q

What factors influence clearance ?

A

Filtration, reabsorption, active secretion and ion trapping

44
Q

What renal factors influence clearance?

A

Filtration, Reabsorption, active secretion

45
Q

Effect of reabsorption on clearance?

A

Reduces clearance

46
Q

Effect of active secretion on clearance?

A

Increases clearance

47
Q

How does ion trapping influence clearance?

A

Urinary PH fan influence clearance Alkalinity increases clearance

48
Q

What is clearance of warfarin?

A

3ml/min

49
Q

What is clearance of propranolol ?

A

840 ml/min

50
Q

What is clearance of diazepam?

A

27 ml/min

51
Q

What is clearance of Lidocaine?

A

640 ml/min

52
Q

What is an inhibitor of cytochrome p450?

A

Ketoconazole

Biomedical Pharmacology (19 decks)

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