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Pharmacology > Pharmacodynamics - Quiz 1 > Flashcards

Pharmacodynamics - Quiz 1 Flashcards

1
Q

What is the MDRD calculation?

A

Modified Diet and Renal Disease Calculation.

More accurate calculation for excessive body weight and renal dysfunction

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2
Q

What is the actual name of the CrCl equation?

A

Cockcroft-Gault Equation

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3
Q

What is a normal CrCl level?

A

> 90ml/min

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4
Q

A dialysis filter is providing how much CrCl?

A

about 30 ml/min

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5
Q

How do you know if a molecule is likely to be removed during dialysis?

A

Unbound volume < 3.5 L/kg
Clearance < 10 ml/min/kg
Dosing interval longer than half life
Molecular weight less than 1000 daltons

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6
Q

Describe the single dose drug concentration

A

Quick upstroke then eliminates based on ½ life – until eliminated. One time single dose will just peak over toxic range.

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7
Q

Describe the concentration of a continuous IV infusion

A

maintenance keeps concentration in therapeutic range (between minimum effective and toxic range). Good for meds quickly eliminated (levo)

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8
Q

Describe the concentration of intermittent dosing

A

Get “about average” good consistent peaks and troughs. Goal is to reach steady state.

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9
Q

What is steady state?

A

rate in = rate out

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10
Q

How many half lives does it take to reach steady state?

A

5 half lives

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11
Q

Does a loading dose shorten the time to steady state?

A

No. Can get you to therapeutic concentrations. But you are not a steady state where your body is truly eliminating until 5 half lives

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12
Q

Would you reach steady state faster if the dose was given at one half of the medication’s half life?

A

No, all you are doing is increasing the rate in and putting them at risk of being toxic.

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13
Q

How do you interpret and treat drug levels?

A

ALWAYS treat the patient, not the number

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14
Q

Troughs are measured for

A

efficacy

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15
Q

Peaks are measured for

A

toxicity

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16
Q

Age related pharmacokinetic changes in the elderly

A
  • Reduced absorption via carrier proteins
  • Reduced first pass metabolism
  • INCREASED fat%, reduced free water
  • Possible reduced albumin concentration and/or increased alpha-1 acid glycoprotein
  • Reduced Phase I metabolism (CYP450)
  • Reduced kidney function
  • Other disease states, thinning BBB, GI tract changes
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17
Q

Age related pharmacokinetic changes in neonates and infants

A
  • Higher gastric pH, longer emptying time
  • Higher body water:fat ratio
  • Reduced/immature CYP450 enzymes
  • Reduced protein binding
  • Reduced renal clearance
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18
Q

What is the “sweet age range” for kinetics

A

25-65

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19
Q

What is pharmacodynamics?

A

What the medication does to the body

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20
Q

Most drugs bind to ______ ______ where they initiate biochemical reactions that alter the cell’s physiology.

A

cellular receptors

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21
Q

Drugs exert their primary action at the

A

Cellular level

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22
Q

What are the drug receptors at the cellular level?

A

generally proteins or glycoproteins present on the cell surface, on an organelle within the cell or in the cytoplasm

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23
Q

How many receptors are on a given cell?

A

A finite number

24
Q

Once a drug has bound to a receptor, one of the following actions is likely to occur

A

An ion channel is opened or closed.

Biochemical messengers, often called second messengers, (cAMP, cGMP, Ca++, inositol phosphates) are activated.

A normal cellular function is physically inhibited or initiated.

25
Q

The biochemical messengers on G-Proteins are often call ________ and they cause a __________ __________ in the receptor.

A

G-Protein

Confirmational Change

26
Q

What is affinity

A

strength of binding between a drug and its receptor.

27
Q

What is Dissociation Constant (Kp)

A

the measure of a drug’s affinity for a given receptor. The concentration of drug required in solution to achieve 50% occupancy of its receptors.

28
Q

What is an agonist

A

drugs which alter the physiology of a cell by binding to plasma membrane or intracellular receptors.

29
Q

What is a strong agonist?

A

an agonist which causes maximal effects even though it may only occupy a small fraction of receptors on a cell.

30
Q

What is a weak agonist?

A

an agonist which must be bound to many more receptors than a strong agonist to produce the same effect.

31
Q

What is an antagonist?

A

inhibit or block actions caused by agonists.

32
Q

What is a competitive antagonist?

A

Competes with agonist for same receptors.
During the time that a receptor is occupied by an antagonist, agonists cannot bind to the receptor.
Because the antagonism can be overcome by high doses of agonists, competitive antagonism is said to be “surmountable”

33
Q

What is noncompetitive antagonists?

A

Binds to a site other than the agonist-binding domain. Induces a conformational change in the receptor such that the agonist no longer “recognizes” the agonist-binding domain.
“Insurmountable” because even high doses of agonist cannot overcome this antagonism.

34
Q

What is irreversible antagonism?

A

Agents compete with agonists for the agonist-binding receptor. Irreversible antagonists combine permanently with the receptor.
(e.g. Plavix)

35
Q

What is efficacy?

A

The degree to which a drug is able to cause maximal effects.

If Drug A reduces blood pressure by 20mmHg and Drug B reduces blood pressure by 10mmHg, then Drug A has greater efficacy than Drug B.

36
Q

What is potency?

A

The amount of drug required to produce 50% of the maximal response that the drug is capable of causing.

For example, morphine and codeine are both capable of relieving post-op pain. A smaller dose of morphine than codeine is required to achieve this effect. Morphine, is therefore more “POTENT” than codeine.

37
Q

“Potency” is frequently used to compare drugs within

A

the same chemical class

38
Q

“Efficacy” is used to compare drugs with

A

different mechanisms

For example, toradol (NSAID) has equal efficacy to morphine (narcotic) in controlling post-op pain.

39
Q

What is the dose respires curve?

A

Response of concentration in the body in response to dose over time.

40
Q

What is the therapeutic window?

A

space between safety and efficacy

41
Q

Effective Concentration 50%

A

The concentration of drug which induces a specified clinical effect in 50% of the subjects to which the drug is administered.

42
Q

Lethal Dose 50%

A

the concentration of drug which induces death in 50% of the subjects to which the drug is administered.

43
Q

Therapeutic Index

A

a measure of the safety of a drug.

44
Q

Margin of Safety

A

the margin between therapeutic and lethal doses of a drug.

45
Q

What is altered absorption

A

Drugs may inhibit absorption of other drugs across biologic membranes

(antiulcer agents that coat the stomach may decrease GI absorption of other drugs)

46
Q

What is altered metabolism:

A

Clinically important drug interactions can occur when the P450 isoenzymes are inhibited or induced.

47
Q

What is plasma protein competition:

A

Drugs that bind to plasma proteins may compete with other drugs for the protein binding sites.

Displacement of drug ‘A’ from plasma proteins by drug ‘B’ may increase the concentration of unbound drug ‘A’ to toxic levels.

48
Q

What is altered excretion:

A

Drugs may act on the kidney to reduce excretion of specific agents

(e.g. probenecid competes with sulfonamides for the same carrier, increasing the risk of sulfonamide toxicity).

49
Q

Types of Drug Interactions: Addition

A

the response elicited by combined drugs is EQUAL TO the combined responses of the individual drugs.

1+1=2

50
Q

Types of Drug Interactions: Synergism

A

the response elicited by combined drugs is GREATER THAN the combined responses of the individual drugs.

1+1=3

51
Q

Types of Drug Interactions: Potentiation

A

A drug which has no effect enhances the effect of a second drug.

0+1=2

52
Q

Types of Drug Interactions: Antagonism

A

Drug inhibits the effect of another drug. Usually, the antagonist has no inherent activity.

1+1=0

53
Q

What is tolerance?

A

Tolerance represents a decreased response to a drug. Clinically, this is observed when the dose of a drug must be increased to achieve the same effect.

54
Q

What is metabolic tolerance?

A

drug is metabolized more rapidly after chronic use.

55
Q

What is cellular tolerance?

A

decreased number of receptors, “down regulation”.

56
Q

What is dependance?

A

Dependence occurs when a patient needs a drug to “function normally”. (do ADLs)
Clinically this is noted when cessation of a drug produces withdrawal symptoms.

57
Q

What is withdrawal?

A

Withdrawal occurs when a drug is not administered to a person who has become dependent on it.

Symptoms of withdrawal are often opposite the effects achieved by the drug. (Benzo withdrawal = anxiety/agitation)

Pharmacology (8 decks)

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