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Pharmacology > Elementary Pharmacokinetics > Flashcards

Elementary Pharmacokinetics Flashcards

1
Q

What is the minimum effective concentration (MEC)

A

The critical concentration a drug must reach in the plasma to achieve an effect

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2
Q

What is the maximum tolerated concentration?

A

The concentration of a drug that will cause a significant unwanted effect

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3
Q

How do you calculate the therapeutic window?

A

TR = MTC/MEC

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4
Q

What constitutes a safe drug?

A

If it has a high ratio and therefore the space between the MEC and MTC is large. An example is penicillins and benzodiazepines

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5
Q

What constitues an unsafe drug?

A

A drug that has a low ratio and therefore the MEC is very close to the MTC. An example is cardiac glycosides and barbiturates

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6
Q

What is pharmacokinestics?

A

The mathmatical analysis of all drug disposition factors (absorption, distribution, metabolism and excretion)

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7
Q

What, simply, is the human body made up of?

A

A single, well-stirred compartment of volume of distribution.

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8
Q

What rate is a drug added to the compartment by absorption at?

A

Kabs

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9
Q

What rate is a drug removed from the compartment by?

A

Kel

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10
Q

What is by-passed if the drug is added IV?

A

Absorption

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11
Q

How do you calculate the initial concentration?

A

Initial concnetration = Dose/volume of distribution

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12
Q

What do most drugs exhibit?

A

First order kinetics where the rate of elimination is directly proportional to drug concentration

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13
Q

What is the half life?

A

The time taken for the concentration to fall by 50%. It is inversely related to Kel:
T1/2 = 0.7/Kel

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14
Q

What does the dose administered affect in first order kinestis?

A

It will change the concentration in direct proportion but will not affect the rate of elimination or the half life

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15
Q

What is clearance?

A

The volume of plasma that is cleared of the drug is a unit time. It is a constant that related the rate of elimination to plasma concentration

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16
Q

What does clearance determine?

A

The maintenance dose rate - the dose per unit time that is needed to maintain a given plasma concentration

17
Q

How is the rate of elimination calculated?

A

Rate of elimination = clearance x plasma concentration

18
Q

What is the steady state?

A

At steady state, the rate of drug administration is equal to the rate of drug elimination

19
Q

How is the rate of elimination calculated at a steady state?

A

Rate of elimination at steady state = clearance x plasma concentration at steady state

20
Q

How is the plasma concentration at a steady state calculated?

A

Maintenance dose rate / clearance

21
Q

What is clearance the total sum of?

A

Renal, hepatic and other clearance

22
Q

What is the steady state of first order kinetics related to?

A

The plasma concentration and steady state are lineraly related to the infusion rate.

23
Q

What is the time to reach the plasma concentration determined by?

A

The half life, but not the infusion rate. The plasma concentration is reached after approx 5 half lives

24
Q

What is F?

A

The oral bioavailability of the drug i.e. the fraction of the drug administrated that enters the systemic circulation

25
Q

How does dosing to a steady state differ in oral administration to IV?

A

The plasma concentration will fluctuate about an average steady state value and so the graph is bumpy but will reach the steady state at the same time

26
Q

What is the volume of distribution?

A

The volume into which a drug appears to be distributed with a concentration equal to that of he plasma

27
Q

How is the amount of drug in the body (Ab) calculated?

A

Ab = Vd x Cp

28
Q

What is the loading dose?

A

An initial higher dose of a drug that is given at the beginning of a course of treatment before stepping down to a lower maintenance dose

29
Q

When is a loading dose used?

A

To decrease the time taken to reach the steady state in drugs with a long half life

30
Q

How is the loading dose estimated?

A

The Vd of the drug.
LD = Vd x target Cp for IV
LD = Vd x Target Cp/F for oral administration

31
Q

What is zero order kinetics?

A

Drugs are eliminated at a constant rate instead of in first order where they are eliminated at a rate that is proportional to their concentration

Pharmacology (4 decks)

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