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Abbey MSII Unit 1 pt 2 > Pharm 3. > Flashcards

Pharm 3. Flashcards

1
Q

What volume is the plasma approximately?

A

3L

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2
Q

What volume is the interstitial fluid approximately?

A

9L

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3
Q

If a drug can cross the capillary membrane, what is the total volume it is in?

A

12L

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4
Q

What volume is the intracellular fluid?

A

28L

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5
Q

If a drug can cross the cells membrane, what is the total volume it is in?

A

40L

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6
Q

What is the equation for volume of distribution of a drug?

A

Vd = dose / Cp (concentration in plasma)

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7
Q

If the volume of distribution is large, what does that say about the drug?

A

It is dissolved over more body fluid

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8
Q

How can you find the volume of distribution using liters and kg?

A

Vd = L / Kg

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9
Q

How are doses for average adults determined?

A

established in volunteer trials - standard doses vs. weight based vs BSA

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10
Q

How are doses for pediatrics determined?

A

weight based dosing (mg/Kg)

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11
Q

What is the effect of protein binding a drug?

A

can be stuck in plasma - may need a loading dose Vd = 3L

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12
Q

What is the effect of high degree of tissue binding

A

High apparent Vd > 40L

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13
Q

Vi

A

plasma volume

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14
Q

Vt

A

total Vd

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15
Q

What are the factors affecting distribution?

A

blood flow (distribute first to vascular organs), ability of drug to enter fluid space (pH, binding, transport, lipid, etc), time after administration, redistribution, size of patient

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16
Q

What is the special consideration for distribution with the placenta?

A

placenta has no barrier to drugs that are

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17
Q

blood brain barrier

A

anatomical protective barrier - created by existence of tight junctions between capillary endothelial cells and the choroid plexus cells in ventricles

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18
Q

How does a drug enter the CNS?

A

lipid soluble or transported by a carrier mediated mechanism

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19
Q

What are the consequences of the BBB?

A

can affect apparent drug potency, may need lipid soluble precursors of active drug (dopa-dopamine), will create special problems in treating overdoses, may necessitate the direct injection of certain drugs into CNS

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20
Q

What will increasing the plasma pH produce in the brain?

A

shift of weak acid drug from brain to plasma

21
Q

What will decreasing the plasma pH produce in the brain?

A

shift of weak base drug from brain to plasma

22
Q

What effect does protein binding have on apparent Vd?

A

becomes larger if tissue binding occurs and smaller if plasma protein binding occurs

23
Q

What effect does protein binding have on the physiologic system?

A

can result in unexpected drug toxicity - because act as reservoirs of active drugs - if a second drug is introduced that has a higher affinity for the same plasma protein than the first drug, this will cause toxicity of the first drug

24
Q

loading dose

A

may need to fill the storage sites before enough free drug is available to interact with receptor

25
Q

short term drug storage

A

protein binding

26
Q

long term drug storage

A

lipid binding or bone

27
Q

drug displacement = ?

A

more free drug at receptor = greater pharmacologic response

28
Q

What are the purposes of biotransformation?

A
  1. drug detoxification 2. prepare drug for excretion
29
Q

How is a drug prepared for excretion?

A
  1. make drug larger 2. add positive or negative charges 3. make drug more water soluble
30
Q

What are the sites of biotransformation?

A

liver esp. smooth ER, cytoplasm, and mitochondria. can happen anywhere else in the body as well

31
Q

induction

A

increase metabolism of the primary drug or other drugs - might be observed as an increase in first pass metabolism

32
Q

inhibition

A

use a drug to block the metabolism of another drug or endogenous compound

33
Q

What is the most common metabolic transformation? Example?

A

drug oxidation (ex. ethanol -> acetaldehyde)

34
Q

What are the components of hepatic mixed function oxidase system? (i don’t think this is important……)

A
  1. NADPH (reducing agent) 2. cytochrome P450 reductase (lends electrons) 3. cytochrome P450 4. Mg++ 5. phospholipid 6. O2
35
Q

What does the hepatic mixed function oxidase system usually metabolize?

A

lipid soluble drugs

36
Q

What are P450 characteristics?

A
  1. 12 P450 groups in humans both for toxic drugs and endogenous compounds 2. low specificity 3. large genetic variations 4. catalyze primarily oxidations but also some reductions
37
Q

Why is the diversity of P450s important?

A

reduce the chance of inhibition

38
Q

What is the P450 system influenced by?

A

disease factors (liver), age, sex, multiple drugs using same enzyme

39
Q

drug reductions

A

add hydrogen or change the proportion of hydrogen in the molecule

40
Q

drug hydrolysis

A

cleave a molecule by the addition of a water molecule

41
Q

What are phase I reactions?

A

activities of drugs vs activities of metabolites - may be sufficient for excretion or may prepare the drug molecule for phase II

42
Q

What are phase II reactions?

A

liver - conjugation - synthesize a new molecule by combining the drug or metabolic product of phase I with a molecule provided by the cell. resulting molecule is larger, charged, water soluble, inactive

43
Q

What do hepatic microsomal enzymes do?

A

induction (increase metabolism), inhibition (decrease metabolism), saturation

44
Q

What do non-microsomal enzymes do?

A

inhibition ONLY, saturation

45
Q

When do enzyme systems have a rate limiting step in the clearance of drug from plasma?

A
  1. when metabolism is more important than renal elimination 2. “rate limiting step” for clearance when enzyme is relatively slow
46
Q

What is the equation for the velocity of metabolism?

A

V = Vmax [D] / Km + [D] D = drug concentration

47
Q

If D

A

efficient enzyme systems = first order ( a proportion of drug is being metabolized per unit of time no matter concentration

48
Q

If D&raquo_space; Km in the velocity of metabolism equation then……

A

inefficient enzyme systems (V = Vmax) - zero order - system is saturated, overwhelmed. only metabolizing an amount as opposed to a proportion

Abbey MSII Unit 1 pt 2 (21 decks)

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