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0. Foundations of Medicine > Metabolism and Pharmacokinetics > Flashcards

Metabolism and Pharmacokinetics Flashcards

1
Q

<p>What is drug metabolism?</p>

A

<p>Biochemical modification of pharmaceutical sibstances by living organisms usually through specialised enzymatic activity</p>

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2
Q

<p>What does metabolism limit?</p>

A

<p>The life of a substance in the body by rendering lipid soluble and non-polar compounds to water soluble and polar compounds than can be excreted</p>

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3
Q

<p>What substances are excreted?</p>

A

<p>Water soluble</p>

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4
Q

<p>What substances are reabsorbed back into the blood from renal sites?</p>

A

<p>Lipid soluble</p>

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5
Q

<p>What are some sites of drug metabolism?</p>

A

<p>Liver</p>

<p>Lining of gut</p>

<p>Kidneys</p>

<p>Lungs</p>

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6
Q

<p>What is the purpose of drug metabolism?</p>

A

<p>Increase water solubility and aid excretion</p>

<p>Deactivate compounds</p>

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7
Q

<p>What are prodrugs?</p>

A

<p>Drugs that may be activated following metabolism</p>

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8
Q

<p>What are examples of prodrugs?</p>

A

<p>Codeine</p>

<p>Enalpril</p>

<p>Simvastatin</p>

<p>Sacbitril</p>

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9
Q

<p>What are the effects of metabolism?</p>

A

<p>Loss of pharmacological activity</p>

<p>Decrease in activity, with metabolites that show some activity</p>

<p>Increase in activity, more active metabolites (activation of prodrug)</p>

<p>Production of toxic metabolites</p>

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10
Q

<p>What can different kinds of toxic metabolites do?</p>

A

<p>Direct toxicity</p>

<p>Carcinogenesis (formation of a cancer)</p>

<p>Teratogenesis (congenital malformations produced in an embryo)</p>

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11
Q

<p>What is carcinogenesis?</p>

A

<p>Formation of a cancer</p>

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12
Q

<p>What is teratogenesis?</p>

A

<p>Congenital malformations produced in an embryo</p>

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13
Q

<p>What happens to a prodrug during metabolism?</p>

A

<p>Inactive chemical compound is coverted into its active metabolite</p>

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14
Q

<p>What controls the metabolism of drugs?</p>

A

<p>Enzymes</p>

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15
Q

<p>What can you say about the specificity of enzymes that metabolise drugs?</p>

A

<p>They have a wide range of specificity so individual drugs are often metabolised by more than one</p>

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16
Q

<p>How can different enzymes be expressed?</p>

A

<p>Constitutively (constant amounts)</p>

<p>In the presence of particular substance</p>

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17
Q

<p>What are the 2 phases of metabolism?</p>

A

<p>Phase 1 (activation/inactivation)</p>

<p>Phase 2 (conjugation products)</p>

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18
Q

<p>What are different phase 1 reactions?</p>

A

<p>Oxidation</p>

<p>Reduction</p>

<p>Hydrolysis</p>

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19
Q

<p>What happens during phase 1?</p>

A

<p>Polar groups are introduced to the molecule</p>

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20
Q

<p>What does increasing the polarity of compounds during phase 1 do?</p>

A

<p>Provides an active site for phase 2 metabolism</p>

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21
Q

<p>What is the most important superfamily of metabolising enzymes?</p>

A

<p>Cytochrome P-450</p>

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22
Q

<p>What doesdrug specificity of an enzyme depend on?</p>

A

<p>Which isoform of cytochrome P-450 is being used</p>

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23
Q

<p>What are the 3 families of the cytochrome P-450 super family used in oxidative drug metabolism?</p>

A

<p>CYP1</p>

<p>CYP2</p>

<p>CYP3</p>

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24
Q

<p>What is CYP1A2 important in the metabolism of?</p>

A

<p>Theophylline</p>

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25
Q

<p>What is CYP1A2 induced by?</p>

A

<p>Smoking</p>

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26
Q

<p>What is CYP2D6 important for the metabolism of?</p>

A

<p>Some antidepressants, antipsychotics and conversion of codeine to morphine</p>

27
Q

<p>What is CYP2D6 induced by?</p>

A

<p>Smoking</p>

28
Q

<p>Where is CYP3A4 found?</p>

A

<p>In the liver and the gut</p>

29
Q

<p>What is CYP3A4 important for?</p>

A

<p>Pre-systematic (first pass) metbaolism of several drugs</p>

30
Q

<p>What are examples of drugs that CYP3A4 is important for the metabolism of?</p>

A

<p>Diazepam</p>

<p>Methadone</p>

<p>Simvastatin</p>

<p>CCBS</p>

31
Q

<p>What can you say about smokers and drugs that are metabolised by the cytochrome P-450 family?</p>

A

<p>They require a higher dose of drugs than non-smokers to achieve the same desired effect</p>

32
Q

<p>What does phase 2 metabolism involve?</p>

A

<p>Conjugation</p>

33
Q

<p>What does conjugation during phase 2 do?</p>

A

<p>Increases water solubility and enhances excretion of the metabolised compound</p>

<p>Usually resulting in inactivation however a small number of drug metabolites may be active</p>

34
Q

<p>What does conjugation involve?</p>

A

<p>Attachment of glucuronic acid, glutathione, sulphate or acetate to the metabolite generated by phase 1 metabolism</p>

35
Q

<p>What does a endogenous molecule do during phase 2 metabolism?</p>

A

<p>A molecule endogenous (inside) the body donates a portion of itself to the foreign molecule (the drug)</p>

<p></p>

<p>D+ENDOX→DX+ENDO</p>

36
Q

<p>What does endogenous mean?</p>

A

<p>Inside</p>

37
Q

<p>What are some factors that affect metabolism?</p>

A

<p>Other drugs</p>

<p>Genetics</p>

<p>Hepatic blood flow</p>

<p>Liver disease</p>

<p>Age</p>

<p>Sex</p>

<p>Ethnicity</p>

<p>Pregnancy</p>

38
Q

<p>What is enzyme induction?</p>

A

<p>Process where a molecule (such as a drug) induces (enhances)the expression of an enzyme</p>

39
Q

<p>What does enzyme induction result in?</p>

A

<p>Increased metabolism of the drugs metabolised by that enzyme, decreasing the drug effect</p>

40
Q

<p>What are common enzyme inducers?</p>

A

<p>Alcohol</p>

<p>Cigarettes</p>

41
Q

<p>What is enzyme inhibition?</p>

A

<p>Substances which inhibit the expression or function of metabolising enzymes</p>

42
Q

<p>How may enzyme inhibitors bind to enzymes?</p>

A

<p>Reversibly or irreversibly</p>

43
Q

<p>What are some common enzyme inhibitors?</p>

A

<p>Cimetidine</p>

<p>Erythromycin</p>

<p>Clarithromycin</p>

<p>Ketoconazole</p>

<p>CCBS</p>

<p>Grapefruit</p>

44
Q

<p>What are possible consequences of there being a wide variation in the response to drugs between individuals?</p>

A

<p>Therapeutic failure</p>

<p>Adverse drug reactions</p>

45
Q

<p>What is pharmacogenetics?</p>

A

<p>The study of inherited genetic differences in drug metabolic pathways which affects an individual's response to a drug</p>

46
Q

<p>What can gene mutations result in?</p>

A

<p>Deficiencies or absence of a particular metabolising enzyme</p>

47
Q

<p>What does decreased activity in enzymes result in?</p>

A

<p>Increased drug toxicity</p>

48
Q

<p>What does multiple expressions of a particular enzyme result in?</p>

A

<p>Reduced drug effect or drug resistance due to increased metabolism</p>

49
Q

<p>What is polymorphism?</p>

A

<p>Discontinuous genetic variation resulting in the occurrence of several different forms or types of individuals amount the members of a single species</p>

50
Q

<p>What are the 4 phenotype subpopulations of metabolisers?</p>

A

<p>Poor metabolisers (PM)</p>

<p>Intermediate metabolisers (IM)</p>

<p>Extensive metabolisers (EM)</p>

<p>Ultrarapid metabolisers (UM)</p>

51
Q

<p>What is CYP2C9?</p>

A

<p>The gene that codes for cytochrome P450 2C9</p>

52
Q

<p>What does cytochrome P450 2C9 do?</p>

A

<p>Metabolises 16 commonly used drugs such as warfarin and phenytoin</p>

53
Q

<p>What is CYP2C19?</p>

A

<p>Gene that codes for cytochrome P450 oxidase 2C</p>

54
Q

<p>How many allelic varients are there for cytochrome P450 oxidase 2C?</p>

A

<p>8</p>

55
Q

<p>What can you say about all the allelic variants of cytochrome P450 oxidase 2C and what does this mean for dosage of drugs?</p>

A

<p>They are all non-functional and so dose adjustments must be made for poor metabolisers of drugs that these enzymes act on such as S-mephenytoin</p>

56
Q

<p>What are some enzymes that exhibit genetic variation?</p>

A

<p>Pseudocholinesterase</p>

<p>N-Acetyltransferase</p>

<p>Cytochrome P450 2D6</p>

<p>Cytochome P450 2C19</p>

<p>TMPT</p>

<p>Dihydropyrimidine dehydrogenase</p>

57
Q

<p>How do infants metabolise drugs compared to adults?</p>

A

<p>Slower</p>

58
Q

<p>Why do infants metabolise drugs slower than adults?</p>

A

<p>Deficient enzymes</p>

<p>Worse renal function</p>

59
Q

<p>When can children metabolise drugs faster than adults?</p>

A

<p>At 2 and at puberty</p>

60
Q

<p>Why do the elderly metabolise drugs differently to adults?</p>

A

<p>Plasma protein</p>

<p>Lean body mass</p>

<p>Liver weight</p>

<p>More common chronic disease</p>

61
Q

<p>What is responsiveness to certain drugs different between?</p>

A

<p>Men and woman</p>

62
Q

<p>What causes a profound change to drug metabolism in woman?</p>

A

<p>Pregnancy</p>

63
Q

<p>Why may race affect drug metabolism?</p>

A

<p>Due to differences in genetic expression of cytochrome P450 isoforms</p>

64
Q

<p>Why is knowing about absorption, distribution, metabolism and excretion important?</p>

A

<p>Determining how to get the drug to the site of action</p>

<p>Determining the dose and frequency</p>

<p>Making sure the drug is present in an effective dose</p>

<p>Predicting and avoiding toxicity</p>

<p>Making changes based on other drugs, illness or physiological factors</p>

0. Foundations of Medicine (167 decks)

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