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MBBCh 1- ELEN1009A > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

• Administration regimens using Vensim: (3)

A

– STEP function
– PULSE function
– PULSE TRAIN function

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2
Q

What is pharmacokinetics? (3)

A 
• Branch of pharmacology
• Rates at which drugs are:
– Absorbed
– Distributed 
– Metabolised 
– Eliminated
• How drugs move within the body
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3
Q

• So far we’ve considered rates that are
– Constant
– Exponential
– Always started at time zero
However, drug administration regimens… (2)

A

– Not always constant

– Don’t always start at time zero

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4
Q

• In Vensim we have a set of functions:

A

– STEP function
– PULSE function
– PULSE TRAIN function

NOTE: Dose = rate x duration

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5
Q

What does the graph for a constant rate for a ZOS look like?

A
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6
Q

What is a step function?

A 
• Constant rate 
– ZOS
• Step Function
– Does not start at zero
• Application
– Intravenous drip
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7
Q

How do you work out the step?

A
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8
Q

What are the applications of a pulse function?

A
  1. Bolus injection
    • Single large dose delivered over a short period
    • Generally given when patient requires meds immediately in bloodstream
  2. Ingesting a single dose of drugs
    • A pill or multiple pills taken over a short period
    • e.g. Analgesia (pain killers)
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9
Q

A pulse function is not ____.

A

repeated

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10
Q

What does the graph for a pulse function look like?

A
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11
Q

What is the area under the rate curve of the pulse function?

A

𝐴𝑟𝑒𝑎 𝑢𝑛𝑑𝑒𝑟 𝑅𝑎𝑡𝑒 𝑐𝑢𝑟𝑣𝑒 = h𝑒𝑖𝑔h𝑡 ∗ 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛

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12
Q

The area under Rate curve of pulse function =

A

Change in Level (Dose)

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13
Q

What is the formula for the dose of a pulse function?

A

𝐷𝑜𝑠𝑒 = h𝑒𝑖𝑔h𝑡 ∗ 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛

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14
Q

What is the formula for the height of a pulse function?

A

1 h𝑒𝑖𝑔h𝑡 = 𝐷𝑜𝑠𝑒 ∗ 1/𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛

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15
Q

What are the applications of a pulse train function?

A
  1. Series of bolus injections
    • Repeated single large doses delivered over short periods
  2. Ingesting a single dose of drugs at regular intervals
    • A pill or multiple pills taken over a short period
    • e.g. Antibiotics; hormone replacement drugs
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16
Q

Consistent time between ___ for a pulse train function.

A

doses

17
Q

What is the pulse train function graph?

A
17
Q

What is the pulse train function graph?

A
18
Q

What is the function equation?

A

height * PULSE TRAIN ( start , dur , rt , end )

19
Q

What is the importance of a time step? (2)

A
  • Extremely important with pulses

* Too large and you can miss pulse completely

19
Q

What is the importance of a time step? (2)

A
  • Extremely important with pulses

* Too large and you can miss pulse completely

20
Q

In Vensim, dose = ____.

A

Dose = rate x duration

21
Q

What is the importance of modelling of a single compartment model? (3)

A

– Simplifying assumption
– Makes analysis easier
– Modelling the body as one single compartment

22
Q

What are the units of the auxiliary variable?

A
23
Q

What is clearance? (3)

A

• Important concept in system dynamics
• Dimensional consistency but there is a slightly
more subtle meaning
• Allows us to use:
– Concentration of drug instead of the absolute amount of drug
– FOS elimination

24
Q

What type of value is clearance and what is the equation for clearance? (2)

A

• Clearance is a constant value
– Characteristics of a FOS
– Modified version of rate constant (k) SCALED by Volume of Distribution (V)
𝑐𝑙𝑒𝑎𝑟𝑎𝑛𝑐𝑒 = 𝑘 ∗ 𝑉

25
Q

How would the clearance variable appear on an LRD?

A
26
Q

What is the formula for the amount of the drug (level) ?

A

𝐴 = ∫ 𝐴𝑑𝑚𝑖𝑛𝑖𝑠𝑡𝑟𝑎𝑡𝑖𝑜𝑛 − 𝐸𝑙𝑖𝑚𝑖𝑛𝑎𝑡𝑖𝑜𝑛 𝑑𝑡

27
Q

What is the formula for the concentration of the drug?

A

Level/Volume

28
Q

What is the formula for clearance?

A

𝑐𝑙𝑒𝑎𝑟𝑎𝑛𝑐𝑒 = 𝑘 ∗ 𝑉

29
Q

What is the formula for the elimination rate?

A

𝐸𝑙𝑖𝑚𝑖𝑛𝑎𝑡𝑖𝑜𝑛 = 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 ∗ 𝑐𝑙𝑒𝑎𝑟𝑎𝑛𝑐𝑒

30
Q

What are the characteristics of administration? (2)

A

• Administration
– Repeats at regular intervals (PULSE TRAIN)

height * PULSE TRAIN ( start , dur , rt , end )

31
Q

For administration:

– start = 10 hours = _____ {minutes}
– dur = 6 seconds = _____ {minutes}
– rt = 12 hours = _____ {minutes}

A

= 10 * 60
= 6 / 60
= 12 * 60

32
Q 
• Administration
– end:
• 3 days, twice daily is 6 doses total
• Must account for the start time and duration to ensure all 6 doses are accounted for
– end = \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.
A

= (1060) first dose + (512*60) time for remaining doses + (6/60) duration {minutes}

33
Q

• Administration
– height:
• Administration is a rate, and the dose is an amount!
• Assume the dose is evenly administered over the duration of each pulse
height = ______________.

A

h𝑒𝑖𝑔h𝑡 = 𝐷𝑜𝑠𝑒 ∗1/𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛

– height = 500 * (60/6) {mg/min}

34
Q

What does the full graph for a pulse train function look like?

A

MBBCh 1- ELEN1009A (18 decks)

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