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Year 1 NME > Pharmacokinetics: Drug Metabolism > Flashcards

Pharmacokinetics: Drug Metabolism Flashcards

1
Q

What does the metabolism of a drug mean?

A
  • process where a drug is chemically altered
  • alteration can activate action of drug
  • alteration can enhances its elimination from the body
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2
Q

What are the 4 different things that can happen to a drug once it has been metabolised?

A

1 - inactive

2 - less active

3 - active (therapeutic/toxic)

4 - activated (pro drug)

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3
Q

What are the 5 main sites in the body where drug metabolism occurs?

A

1 - LIVER (MAIN SITE)

2 - kidney

3 - GIT

4 - lungs

5 - skin

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4
Q

Are there any specific enzymes for the biotransformation (transformation of a molecule from one compound to another, usually to reduce toxicity) of drugs?

A
  • no
  • same enzymes involved in the synthesis and biotransformation of other endogenous and exogenous compounds in the body
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5
Q

What is oxidation and reduction?

A
  • oxidation = loss of electrons (NADH to NAD+)
  • reduction = additions of electrons (NAD+ to NADH)
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6
Q

In drug metabolism enzymes involved in their metabolism are grouped into phase 1 or phase 2 reactions. What are phase 1 reactions?

A
  • also called oxidation/reduction enzymes (losing electrons)
  • cytochrome P450 enzymes
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7
Q

What is oxidation and reduction?

A
  • oxdiation = loss of electrons and H+
  • reduction = addition of electrons and H+
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8
Q

What is phase II reactions, also called conjugation/hydrolysis?

A
  • hydrolysis = breaking molecule with H2O
  • conjugation = adding of molecules (adding electrons)
  • multiple enzyme types
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9
Q

What family of enzymes is responsible for 75% metabolism of all drugs?

A
  • cytochrome P450
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10
Q

What are some functional factors of people that can affect metabolism?

A
  • age (enzymes can increase and decrease wih age)
  • gender
  • pathophysiology (liver/renal disease)
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11
Q

In drug metabolism, if we inhibit or induct a drug what will happen to the drug metabolism?

A
  • inhibit = slow metabolism (less enzymes or activity)
  • induct = increase metabolism (more enzymes or activity)
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12
Q

In drug metabolism, if we can inhibit (slow metabolism (less enzymes or activity) or induct (increase metabolism (more enzymes or activity). What do both of these do to the drug concentration in the body?

A
  • inhibit = higher drug concentration in plasma for longer
  • induct = lower drug concentration in plasma
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13
Q

In the figure below, the what does the bottom of each peak denote?

A
  • time point of drug administration
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14
Q

In the figure below, out of numbers 1 and 2, which denotes the inhibitor and which is the inducer?

A
  • 1 = inducer, faster metabolism and plasma concentration is lower
  • 2 = inhibitor, slower metabolism and plasma concentration is higher
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15
Q

In the figure below what does the black line denote?

A
  • the effects of a drug we would expect
  • no inhibitor or inducer
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16
Q

The therapeutic window describes what?

A
  • minimum dose required for therapeutic effect
  • maximum dose before drug is toxic
17
Q

Out of inducers and inhibitors, which is more likley to cause sub-therapeutics (drug doesnt have enough of an effect) and which is more likley to become toxic?

A
  • inhibitors = toxicity (drug stays in plasma for longer)
  • inducers = sub-therapeutic (drug removed from plasma quickly)
18
Q

Why do we need to be cautious with drugs that are metabolised by cytochrome P450 (CP450)?

A
  • can reduce the therapeutic window
  • warfarin is a good example of this
19
Q

Drugs that are metabolised by cytochrome P450 (CP450) can drastically alter their therapeutic window which can be very dangerous. Using Warfarin as an example, which is metabolised by CP450, what could happen if an inducer or inhibitor was added alongside the drug?

A
  • inducer = reduced metabolism, meaning warfarin would not stop coagulation and you could develop thrombosis
  • inhibitor = increased metabolism, meaning warfarin levels could become toxic in the plasma
20
Q

If we induce or inhibit a drug what happens to the bioavailability (how much of drug is effective at the site) of that drug in the body?

A
  • induce = decreased bioavailability (remove drug quicker)
  • inhibit = increased bioavailabilty (keep drug for longer)
21
Q

If we induce or inhibit a drug what happens to the therapeutic effect of that drug in the body?

A
  • induce = decreased therapeutic effect (remove drug quicker)
  • inhibit = increased therapeutic effect (keep drug for longer)
22
Q

If we induce or inhibit a drug what happens to the toxic effect of that drug in the body?

A
  • induce = decreased toxic effect (remove drug quicker)
  • inhibit = increased toxic effect (keep drug for longer)
23
Q

If we induce or inhibit a drug what happens to the first pass metabolism of that drug in the body?

A
  • induce = increased (more of drug metabolised by liver)
  • inhibit = decreased (less of drug metabolised by liver)
24
Q

If we induce or inhibit a drug what happens to the metabolism of that drug in the body?

A
  • induce = increased (remove drug quicker)
  • inhibit = decreased (keep drug for longer)
25
Q

If a patient is currently taking atorvastatin, which can have side effects of myalgia (muscle pain) and rheumatoid myalgia (joint pain), but is then prescribed the antibiotic clarithromycin, what could happen?

A
  • clarithromycin may inhibit the enzymes responsible for metabolism of atorvastatin
  • this could keep atorvastatin plasma levels higher for longer
  • patient could experience increased myalgia and rheumatoid myalgia as a consequence
26
Q

In terms of drug metabolism, what does pharmacogentics mean?

A
  • how genetics impacts upon metaboims of drugs
27
Q

What does pharmacodynamics mean?

A
  • think Dynamics = Drug effects
  • how Drug affects the body
28
Q

What is a genetic polymorphism?

A
  • NOT a mutation
  • difference in DNA sequence among individuals, groups, or populations
29
Q

Genetic polymorphisms refer to difference in DNA sequence among individuals, groups, or populations. Why is this important in drug metabolism?

A
  • people may have different levels or activity of enzymes
  • means people metabolise drugs differently
30
Q

If someone has a genetic polymorphism that causes a duplicartion of a normal allele (the allele containing the genetic information that codes for the enzyme that metabolises the drug), meaning they have 2 alleles that contain information on an enzyme that metabolises a drug, what does that mean for your metabolism?

A
  • you would be a ultrarapid metaboliser
  • form of induction
31
Q

If someone has a genetic polymorphism that means they have 2 different alleles of a gene (one from mum and dad) that code an enzyme that metabolises a drug what does that mean for your metabolism?

A
  • you are an extensive metaboliser
  • normal metabolism occurs
32
Q

If someone has a genetic polymorphism that causes one abnormal allele and one normal allele for the genes involved in drug metabolism, what does that mean for your metabolism?

A
  • intermediate metaboliser
  • slight inhibitor so slower metabolism
33
Q

If someone has a genetic polymorphism that causes two abnormal allele for the genes involved in drug metabolism, what does that mean for your metabolism?

A
  • poor metaboliser, so acts as a strong inhibitor
  • drug metabolism will be slower and could increase toxicity
34
Q

If a patient is an ultrarapid metaboliser becuase they have a duplication of normal alleles they are able to metabolise drugs quickly, which acts as a form of inducer. However, what would they effect of a an ultrarapid metaboliser on a prodrug be?

A
  • codeine is metabolised super quikly
  • BUT it is metabolised into morphine
  • would result in high levels of morphine in the blood which is dangerous
35
Q

If a patient is an poor metaboliser becuase they have a abnormal alleles they are able unable to metabolise drugs normally, which acts as a form of inhibitor. However, what would they effect of a an ultrarapid metaboliser on a prodrug be?

A
  • codeine is metabolised very slowly, if at all
  • drug may not be metabolised at all so no effect for patient

Year 1 NME (61 decks)

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