Block 09 > pharm: pharmacokinetics 5 > Flashcards

pharm: pharmacokinetics 5 Flashcards

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1
Q

How can drug dosage be determined if the effect of the drug is easily measured like Blood pressure?

A

Through a trial-and-error approach to optimize dosage

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2
Q

What type of drugs are difficult to measure?

A

Seizure meds

Toxicity and lack of efficacy are concerns which makes it difficult to know what the best dose can be.

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3
Q

How many half-lives does it take to achieve steady state?

A

4-5

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4
Q

When does steady-state occur?

A

When the rate of input = Rate of loss

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5
Q

What is the Maintenance dose (MD) equation?

A

Maintenance dose (MD) = Css x CL/F

Css = concentration at steady state, CL = clearance, F = bioavailability

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6
Q

If the desired plasma concentration is 1mg/mL and the CL is 100mL/hr, what should the dose of my continuous IV drug be?

A

100 mg/hr

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7
Q

If the desired plasma concentration is 1mg/mL and the CL is 100mL/hr, what should the dose of my continuous IV drug be every 8 hours?

A

800 mg

100mg/hr x 8 hrs = 800 mg

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8
Q

What is the desired steady-state plasma concentration of theophylline for a 68-kg patient?

A

0.663 mg/min or 40 mg/hr

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9
Q

What is the bioavailability (F) of a drug given IV?

A

1

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10
Q

What would the calculated oral doses be at 6, 8, and 12 hour intervals for theophylline (giving 40mg/hr)?

A

6 hour intervals = 240 mg
8 hour intervals = 320 mg
12 hour intervals = 480 mg

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11
Q

What is the dose that may be given at the onset of therapy to achieve the target concentration rapidly?

A

Loading dose

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12
Q

What is the Loading dose equation?

A

LD = Cs × Vd/F

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13
Q

How would you calculate the loading dose for the asthma patient if the volume of distribution of theophylline is 0.5 L/kg? (SSc=15mg/L)

A

LD = 510 mg

LD = 15 mg/L x 0.5 L/Kg x 68 Kg

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14
Q

If a patient has renal insufficiency, which would you want to adjust?

A

MD

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15
Q

When is a loading dose desirable to give?

A

If the time required to reach steady-state is long relative to the temporal demands of the condition being treated

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16
Q

To ensure the appropriate response to a drug given for long-term therapy, what level of the drug in the plasma is necessary?

A

Steady-state

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17
Q

Steady state is proportional to what rate?

A

Dosing

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18
Q

Steady state is inversely proportional to what rate of the drug?

A

Elimination

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19
Q

What happens to steady-state plasma level if there is an increase in dosing rate without a change in elimination rate?

A

Increase

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20
Q

Factors that affect elimination like liver and kidney disease of the drug will do what to steady-state concentration?

A

Increase

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21
Q

What does the time to steady state depend on?

A

Half-life (t 1/2)

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22
Q

What is the function of the time it takes to reach steady-state for a drug eliminated by first-order kinetics?

A

Half-life

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23
Q

What percentage of the way to steady-state is 1 t 1/2?

24
Q

Every t 1/2 you get how much closer to your goal?

25
It is generally accepted that drugs will reach 'clinical' steady-state in how many half lives?
4-5
26
How does drug elimination occur in relation to the pattern seen for a drug approaching steady-state?
Reverse
27
Drugs are considered eliminated from the body in how many half-lives?
4-5 half-lives
28
If a drug has a t1/2 = 2 hours, how long for the drug to reach clinical SS?
8-10 hours
29
If a drug has a t1/2 = 2 hours, how long to get to 75% SS?
4 hours
30
What percentage of drug is eliminated after 2 half lives?
75%
31
How close to the steady-state is the drug after 1 t 1/2?
50%
32
If theophylline is infused at a rate of 20 mg per hour and steady-state plasma levels of 7.5 ug/ml are reached in 32 hours, how long will it take to reach steady-state if the infusion rate is doubled?
32 hours
33
What is the new steady-state level of theophylline at the infusion rate of 40 mg per hour?
15 ug/ml
34
If a single IV injection of 100 mg of a drug is given and it takes 8 hours to eliminate ½ the drug from the body, how long would it take to eliminate ½ the drug if only 50 mg were given?
8 hours
35
T 1/2 is only constant in what type of kinetics?
First-order
36
Does the half-life of a drug depend on the size of the administered dose?
No
37
The half-life of a drug is unaffected by the amount of drug given as long as the drug is eliminated by what type of kinetics?
First-order
38
What is MEC?
Minimum effective concentration
39
What is MTC?
Minimum toxic concentration
40
The wider the therapeutic window, the less frequently I need to do what?
Dose
41
Is there oscillation around steady-state with a continuous infusion?
No
42
With single or multiple dosing, will there be oscillation around steady-state?
Yes
43
The more frequently a drug is given, the more likely you are to maintain plasma levels close to what?
Steady-state
44
What represents the opening between the minimum therapeutic concentration and minimum toxic concentration?
Therapeutic window
45
What does the MEC usually determine?
The desired trough levels of a drug given intermittently
46
What does the MTC determine?
The permissible peak plasma concentration
47
What is the goal for the steady state to be within?
MEC and MTC
48
What does the steady state being within the MEC and MTC mean for the dose?
Effective and non-toxic
49
How are Clearance (CL) and Volume of distribution (Vd) related?
Inversely proportional
50
What is the corrected dose formula?
Corrected dose = average dose x patients creatinine clearance / 100 mL/min - normal CL
51
What is the normal CL in ml/min?
100 mL/min
52
What dose of celecoxib should be administered (100mg was ordered) to a patient with a creatinine clearance of 50 mL/min?
50 mg
53
What is the Volume of distribution (Vd) equation?
Vd = amount of drug in mg / Cp in mg/L
54
What is the Maintenance Dose (MD) equation?
MD = Css x CL/F
55
What is the Loading Dose (LD) equation?
LD = Cs x Vd/F
56
What is the Corrected Dose (CD) equation?
CD = average (normal) dose x CL / 100 mL/min
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