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Pharmacology > Pharmacokinetics Ctd. > Flashcards

Pharmacokinetics Ctd. Flashcards

1
Q

Define Prodrug

A

Drug given in inactive form and must undergo metabolism to be acctivated

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2
Q

Most phase I reactions involve which enzyme system of the liver?

A

CYP450

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3
Q

What occurs during a phase I reaction?

A

Oxidation reactions that will activate, change, or unchange a drug

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4
Q

What occurs during Phase II reactions

A

Conjugation reactions (most drugs don;t retain therapeutic actions after conjugation

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5
Q

Which CYP450 group is likely to have genetic variability( some people won’t metabolize the medication wekk)

A

2D6

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6
Q
  • What occurs during CYP450 competition?
A

CYP450 competes with other substrates for the CYP450 subgroup enzymes

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7
Q
  • What occurs during CYP450 inhibition
A

Some drugs inhibit CYP450 enzymes

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8
Q
  • What occurs during CYP450 induction?
A

Some drugs induce (enhance) CYP450 enzymes

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9
Q

Name the types of 1A2 substrates

A
  • Tricyclic Antidepressants (TCAs)
  • Warfarin (Coumadin®)
  • Theophylline
  • Caffeine
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10
Q

Name the types of 2C9 substrates

A
  • Non-Steroidal Anti-inflammatories (NSAIDs)
  • Oral hypoglycemics
  • Warfarin (Coumadin®)
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11
Q

Name the types of 2C19 substrates

A

Proton Pump Inhibitors (PPIs)

Antiepileptic drugs

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12
Q

Name the types of 2D6 substrates

A 
Beta Blockers
Antidepressants
TCAs
Selective Serotonin Reuptake Inhibitors (SSRIs)
Antipsychotics
Codeine
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13
Q
  • What is one of the most common 2D6 substrates?
A

Codeine

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14
Q

Name the types of 2E1 substrates

A

Anesthetics
Acetaminophen (Tylenol®)
Ethanol

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15
Q

*Name the types of 3A (4, 5, 7) substrates

A
  • Antibiotics-Macrolides
  • Benzodiazepines (BZDs)
  • Immunosuppressants
  • HIV antivirals
  • Calcium Channel Blockers (CCBs)
  • Statins
  • Hormones (estrogen, progesterone)
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16
Q
  • Describe CYP450 Induction
A

More activity of CYP450 enzymes  Increased metabolism  Lower plasma concentration

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17
Q
  • What effect will CYP450 induction have on an inactive metabolite?
A

Decreased drug activity/therapeutic effect

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18
Q
  • What effect will CYP450 induction have on an active metabolite?
A

Increased drug activity/therapeutic effects

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19
Q
  • What are the overall common CYP450 Inducers?
A
  • Phenobarbital
  • Phenytoin
  • Rifampin
  • Carbamazepine
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20
Q
  • Describe CYP450 Inhibition
A

Less activity of CYP450 decreased metabolism  higher concentration of plasma drug levels possible side effects or toxicity

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21
Q
  • What are the overall common inhinbitors?
A
  • cimetidiIne
  • grapefruit juice
  • amiodarone
  • azole antifungals
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22
Q
  • Which order kinetics do most drugs follow?
A

1st order kinetics

23
Q
  • Describe 1st order kinetics
A

Rate of drug metabolism is directly proportional to the concentration of free drug

24
Q
  • Describe Zero order kinetics
A

Rate of metabolism remains constant over time

25
Q
  • Is zero order kinetics linear or nonlinear?
A

Nonlinear

26
Q

** Which drugs follow zero order kinetics?

A

-Ethanol, Aspirin, Phenytoin

27
Q
  • Which order of kinetics is describes as a constant fraction is eliminated per time?
A

1st order kinetics

28
Q
  • Describe the elimination of zero order kinetics
A

Constant amount of drug is eliminated per time

29
Q

What is the most common route of excretion?

A

Renal

30
Q

What is the purpose of metabolism in Phase I and II

A

To make the compounds more polar, preventing then from reabsorption

31
Q
  • What is the formula for total body clearance?
A

Total body CL=hepatic Cl + renal Cl + other Cl

32
Q

Define extraction ratio

A

decline in drug concentration from the arterial to the venous side of the kidney

33
Q
  • What is the formula for extraction ratio?
A

Extration ratio= C2/C1

  • C1 = concentration of drug entering kidneys
  • C2 = concentration of drug leaving kidneys
34
Q

*What is the formula for clearance?

A

Cl = k * Vd = 0.693 * Vd/t1/2

-k is the elimination constant = 0.693/t1/2

35
Q
  • What is the formula for Excretion rate?
A

Excretion Rate = (Cl) (plasma concentration)

36
Q
  • In the Crockcroft-Gault equation, what value is used for females only?
A

0.85

37
Q

*What is the Crockcroft-Gault Equation (used to adjust dosage in proortion to kidney dysfunction)?

A

CrCl=(140-age) x 1bw/SrCr x 72 (all x 0.85)

38
Q
  • What is the formula for half-life?
A

t½ = 0.693/k

39
Q

Describe steady state concentration

A

When an infusion is started, the plasma concentration rises until the elimination of the drug balances the infusion of the drug.

40
Q

Describe the kinetics of continuous IV infusions

A

Rate of elimination increases as the plasma concentration of drug increases

41
Q

Is steady state concentration inversely or directly proportional to the rate of elimination?

A

Inversely

42
Q

What will occur if the metabolism or the Clearance of a drug is decreased?

A

The steady state concentration increases

43
Q
  • What is the formula for infusion rate?
A

Ko = Css * Cl

44
Q
  • How long does it take a drug to reach steady state?
A

4 half lives

45
Q

Does the drug infusion rate affect the time to reach steady state?

A

No, only the steady state is affected

46
Q

Define loading dose

A

A higher single dose of drug given at the start of therapy to achieve the desired plasma concentration more rapidly

47
Q

*What is the formula for Loading dose?

A

Ld = (Vd)(desired Css)

48
Q

When giving multiple IV injections are the steady state and time required affected?

A

No

49
Q
  • Calculate the Vd when the dose is 120 and the concentration is 4 mg/l
A

Vd = Dose/Concentration

120 mg / 4 mg/L = 30 L

50
Q
  • Calculate the needed dosage adjustment to reach the desired concentration if
  • Vd = 10 L
  • Current concentration = 100 mg/L
  • Desired concentration = 150 mg/L
A

-Vd (C2-C1)

10 L (150 mg/dl – 100 mg/L) = 10(50) = 500 mg

51
Q
  • Calculate the t½ of the drug when

K = 0.23

A 
t½ = 0.693/k
0.693/0.23 = 3 hrs
52
Q
  • Calculate the clearance of the drug when Vd = 42 L

K = 0.38 hr-1

A

Cl = k * Vd

0.38 hr-1 * 42 L = 15.96 L/hr = 266 ml/min

53
Q
  • Calculate the clearance of the drug when Vd = 30 L

t1/2 = 5.4 hr

A 
Cl = 0.693 * Vd/t½
Cl = 0.693 * 30 L / 5.4 hr = 3.85 L/hr = 64.2 ml/min
54
Q

*Calculate estimated CrCl of for a patient

Female, Age 65 years; IBW = 75 kg; SrCr = 1.2 mg/dl

A

CrCl=(140-age) x 1bw/SrCr x 72 (all x 0.85)

(140 – 65) * 75 / 1.2 * 72 = 65.1 ml/min
65.1 * 0.85 = 55.3 ml/min

Pharmacology (5 decks)

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