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Pharmacology > Pharmacokinetics II > Flashcards

Pharmacokinetics II Flashcards

1
Q

What is bioavailability?

A

Amount of free and active unchanged drug that reaches systemic circulation

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2
Q

What mechanism of drug administration typically has 100% absorption?

A

IV

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3
Q

What mechanism of drug administration rarely has 100% absorption?

A

any non-IV route

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4
Q

What can the bioavailability be used to calculate clinically?

A

The equally effective dose between two different routes of administration

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5
Q

How do you calculate effective IV dose?

A

D(iv) = D(oral) x [bioavailability/100]

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6
Q

How do you calculate effective oral dose?

A

D(oral) = D(iv) / [bioavailability/100]

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7
Q

A drug has an oral bioavailability of 40%. An effective oral dose is 100mg. What is the equivalent IV dose?

A

40mg

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8
Q

An effective IV dose is 100mg

and has a bioavailability of 40%. What is the equivalent oral dose?

A

250mg`

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9
Q

What is the first-pass effect?

A

Following oral administration, a significant amount of drug enters the portal blood and may be metabolized in the liver before it reaches the systemic circulation.

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10
Q

Inter-patient variation in ____ can affect plasma drug levels after administration of drugs that have a high first-pass effect.

A

Hepatic function

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11
Q

What is the volume of distribution (Vd)?

A

Relates the amount of drug in the body to the amount of drug in the blood

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12
Q

What is the single compartment model?

A

Apparent volume

that a drug would need to be dissolved in to maintain a homogeneous concentration throughout the body

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13
Q

If a drug is distributed extensively and bound to peripheral tissues, does that indicate a large or small Vd?

A

Large Vd

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14
Q

If a drug is highly concentrated in the plasma, does that indicate a large or small Vd?

A

Small Vd

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15
Q

What compartment of the body does a Vd of 3-5L correlate to?

A

Plasma water (warfarin)

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16
Q

What compartment of the body does a Vd of 10-20L correlate to?

A

Extracellular space (aspirin)

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17
Q

What compartment of the body does a Vd of 22-40L correlate to?

A

Whole body water

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18
Q

What compartment of the body does a Vd of >70L correlate to?

A

Tissue

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19
Q

What are biological storage depots?

A

Sites in the body can accumulate drugs and act as reservoirs; affecting distribution by decreasing plasma levels and prolonging half-lives.

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20
Q

What type of drugs accumulate in adipose tissue?

A

Highly lipid soluble drugs

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21
Q

What kind of drugs accumulate in tissues?

A

Drugs that bind reversibly to cellular components

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22
Q

What kind of drugs accumulate in bone?

A

Drugs with chelating properties

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23
Q

What kinds of drugs accumulate in transcellular reservoirs?

A

Drugs that are slowly absorbed or undergo enterohepatic circulation

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24
Q

What kind of drugs accumulate in the plasma and have prolonged half-lives?

A

Drugs that have high plasma protein

(albumin) binding

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25
Q

If a drug is available but not active does that indicate a low or high Vd?

A

Low Vd (warfarin)

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26
Q

What kind of drugs commonly use redistribution?

A

Lipid soluble drugs are distributed between compartments

27
Q

What type of drugs accumulate in breast milk?

A

Breaks milk is more acidic than plasma, so basic and lipid soluble drugs get trapped

28
Q

What are common sites of drug exclusion in the body?

A

Fluids!

Cerebrospinal fluid; ocular fluid; fetal fluid; pleural fluid

29
Q

What type of drugs are teratogenic?

A

Fetus is acidic, so basic drugs get trapped

30
Q

What occurs by first or zero order kinetics?

A

Elimination

31
Q

First order elimination compares what?

A

Percentage of the drug eliminated/time

32
Q

What is the rate limiting factor of first order elimination?

A

Plasma concentration

33
Q

What is half-life?

A

Time required to decrease the plasma concentration by 50%

34
Q

How do you calculate half -life?

A

t1/2 =(0.7xVd)÷CL

35
Q

What is the t1/2 of a drug with Vd = 40 L and CL of 5 L/hr?

*if given in L assume the patient is 70kg

A

t = (0.7 x 40 L) ÷ 5 L/hr = 5.6 hr

36
Q

What is the t1/2 if Vd = 0.57 L/Kg and CL of 5 L/hr in a 80 Kg man?

A

t1/2 = (0.7 x 0.57 L/Kg x 80 Kg) ÷ 5 L/hr = 6.4 hr

37
Q

How long does it take to eliminate most of a drug?

A

5 half-lives

38
Q

How long does it take to obtain Css (concentration steady-state) plasma levels?

A

5 half-lives

39
Q

Is the time to reach Css related to size of dose?

A

NO DUMB BITCH

40
Q

Is the time to reach Css related to half-live?

A

YASSS QUEEN

41
Q

What will result in increased Css?

A

Shortening the dosing interval (τ) or increasing the dose (D)

42
Q

What will result in decreased Css?

A

Lengthening the dosing interval (τ) or decreasing the dose (D)

43
Q

What is zero order elimination?

A

Constant amount eliminated over unit time

44
Q

What type of elimination has the biological system as the rate limiting factor and is not dependent upon plasma levels or dose?

A

Zero order elimination

45
Q

For a drug with zero order kinetics, if given repeatedly in high doses, will it develop steady state levels?

A

No, because it is not dependent on plasma levels

46
Q

For a drug with zero order kinetics, if given at higher doses than its elimination rate, will it accumulate in the body?

A

Yes, it will accumulate and produce excessive plasma levels and toxicity

47
Q

What is clearance?

A

Measure of body’s capacity to eliminate a drug

48
Q

How do you calculate clearance (CL)?

A

CL=Vd x (0.7÷t1/2)

49
Q

What is the CL of a drug with a Vd = 100 L and t1/2 = 2 hr?

*if given in L assume the patient is 70kg

A

35 L/hr

50
Q

What is the CL if Vd = 100 L and t1/2 = 2 hr in a 80 Kg patient?

A

40 L/hr

51
Q

What is directly proportional to Css?

A

Dose (D), bioavailability(F), and half-life (τ)

52
Q

What is inversely proportional to Css?

A

Clearance (CL), and volume distribution (Vd)

53
Q

What is the goal of a maintenance dose?

A

Drugs are administered in a way so we maintain a steady state concentration (Target Concentration) in the body

Maintenance dose = elimination rate

54
Q

How do you calculate maintenance dose?

A

Maintenance dose = (CL x TC ÷ F) x dosing interval (τ)

55
Q

What is used to achieve immediate therapeutic plasma concentrations (Css)?

A

Loading dose (LD)

56
Q

How do you calculate loading dose?

A

LD = Vd x TC

57
Q

What is the LD if Vd = 100 L and TC = 5 mg/L?

*if given in L assume the patient is 70kg

A

LD = 100 L x 5 mg/L = 500 mg

58
Q

What is the LD if Vd = 100 L and TC = 5 mg/L in a 60 Kg patient?

A

Vd = 100 L ÷ 70 Kg = 1.42 L/Kg

LD = 1.42 L/Kg x 5 mg/L x 60 Kg = 426 mg

59
Q

What are some differences between brand name and generic drugs?

A

Brand name drugs
• Name is protected forever (Tylenol)
• Compound is protected for 20 years (acetaminophen)
• Few exceptions orphan drugs

Generic drugs
• Contain the same active ingredient(s)
• Less expensive

60
Q

`A 23 year old man goes to a party and consumes 5 vodka tonics in the first 10 min he is there. If each drink contains ~10g of ethanol, approximately how long does he have to wait to ensure that his blood alcohol content level is 0.0?

A

5 hours

61
Q

A drug a has an oral bioavailability of 70%. You want to switch the patient from the effective 350 mg IV dose to oral dosing. The equally effective oral dose is:

A

D(oral) = 350 ÷ 0.7 = 500mg

62
Q

Whats an example of a drug with a high first pass?

A

Isoniazid

63
Q

Whats an example of a drug with a low first pass?

A

Diazepam

64
Q

At what rate is ethanol eliminated?

A

10g/hr

Pharmacology (25 decks)

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