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Pathophysiology & Pharmacology > Pharmacodynamics > Flashcards

Pharmacodynamics Flashcards

1
Q

Pharmacodynamics

A
  • Study of how a drug affects the body (Drug Action)
    ~ Physiological effect a drug has
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2
Q

Site of Action

A
  • Molecular site where the drug has a significant chemical interaction, which causes a biological effect
    ~ Takes advantage of receptors
    normally used for endogenous
    chemicals
  • Site of Action
    ~ Surface of internal cell receptors
    ~ Internal cell enzymes
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3
Q

Receptor/Drug Interaction: Receptor

A
  • Molecule within a cell, or on the cell
    membrane
  • Relationship between the drug and
    the receptor is similar to that of a lock
    and key
    ~ Has to do with shape
    > If receptors don’t fit with each
    other, they don’t work
  • Each cell has receptors that are necessary to proper functioning of that specific cell
  • Reaction to changes in chemical concentration
    ~ Increase or decrease the number of
    receptors to adapt to the
    environment
    > Add more receptors when
    chemical levels are low
    > Decrease number of receptors
    when chemical levels are high
    ~ Increase or decrease the sensitivity
    of a receptor
    > Increase sensitivity when
    chemicals are low
    > Decrease sensitivity when
    chemical levels are high
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4
Q

Receptor/Drug Interaction: Effects of Binding

A
  • The drug can directly cause changes
  • The drugs can inhibit the binding of natural chemicals or another drug
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5
Q

Receptor/Drug Interaction: Affinity and Efficacy

A
  • In order for a drug to trigger an effect it must have both affinity and efficacy for a receptor
  • Affinity: chemical structure fits the receptor structure
  • Efficacy: chemical causes a biological response when fit into the receptor
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6
Q

Drug Action Concepts: Additive Effect

A

Effect of taking two or more drugs is equal to the sum of the responses obtained when the drugs are taken individually

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7
Q

Drug Action Concepts: Synergistic Effect

A

Use of one drug enhances the effect of another

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8
Q

Drug Action Concepts: Antagonistic Effect

A

Use of is drug reduces the effect of another

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9
Q

Drug Action Concepts: Placebo Effect

A

Pt. anticipates a specific response and perceives that response despite taking a drug that has no therapeutic effect

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10
Q

Drug Action Concepts: Tolerance

A
  • Diminished response to a drug as a result of continued use. Must take more of a drug to get the desired effects
    ~ Body produces more enzymes
    responsible for metabolism
    ~ Cell reduces number of sensitivity of
    receptors
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11
Q

Dose-Response Relationship

A
  • As the amount of a drug is increased the effects increase since more receptor binding takes place
    ~ Drug/receptor interaction is by
    chance so increasing the dose
    increases the chance of interaction
    ~ When all receptors are occupied,
    increasing dose has no effect
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12
Q

Dose-Response Relationship: Multiple Doses

A
  • The levels of the drug increase and then level off when the amount of drug administered is equal to the amount of drug being eliminated
  • Leveling off is known as steady state
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13
Q

Dose-Response Relationship: Maintenance Dose

A

Dose used to maintain steady state/therapeutic levels of a drug

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14
Q

Dose-Response Relationship: Loading Dose

A
  • One or more doses that are higher than the maintenance dose
  • Used to get to a therapeutic level quicker
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15
Q

Dosing Frequency Abbreviations

A
  • q.d. - once a day
  • quaque (each/every) die (day)
  • q4h - every four hours
  • qam - every morning
  • qpm - every night
  • b.i.d. - twice a day
  • bis (twice) in die
  • t.i.d. - three times a day
  • ter (thrice) in die
  • qi.d. - four times a day
  • quater (four times) in die
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16
Q

Dose Calculations

A
  • Standard doses for drugs are often variable to make sure the amount of drug needed to get the therapeutic effect is taken while allowing safety/effective elimination of the drug
    ~ Children
    > 2-5
    > 6-12
    ~ Adults
    ~ Elderly (reduced ability to metabolize/
    excrete)
  • Most focus is on amount of drug relative to weight or body surface area
17
Q

Why is dose modified for the elderly?

A
  • Diminished blood flow to the liver and function of metabolizing enzymes found in the liver
  • Reduced kidney function
18
Q

Drug Interactions

A
  • Addition of a drug increases or decreases the effect of another
    ~ Not always a negative factor; can be
    used to a therapeutic advantage in
    some situations
19
Q

Drug Interactions: Receptor Antagonist

A
  • Two drugs have affinity (fit) to a receptor
    ~ If one binds to the receptor, the other
    can’t
20
Q

Drug Interactions: Enzyme Induction

A
  • One drug causes increased production of the enzymes that metabolize another drug
  • Remember that the metabolites are usually inactive forms of the chemical, but can also be more active forms
    ~ Usually increases the inactive forms
    so drug is less effective
21
Q

Drug Interactions: Enzyme Inhibition

A
  • One drug binds with the enzymes that metabolize another drug
  • The effects of the second drug are stronger and longer lasting
22
Q

Drug Interactions: Physiological Antagonism

A
  • Physiological effect of one drug is opposite to the physiological effect of another drug
  • Ex: one drug is taken to mange high blood pressure, but the person also has a cold
    ~ ACE inhibitor (vasodilator) vs. Nasal
    decongestants (vasoconstrictor)
23
Q

Drug Interactions: Physiological Agonists

A
  • 2 drugs used at the same time have the same physiological effect, but the exact mechanism of action is different
  • Ex: 2 drugs may decrease pain, but the way they do is different
    ~ Ibuprofen and Morphine
24
Q

Drug Interactions: Absorption Effects

A
  • Use of one drug affects the absorption of another
  • Ex: taking a laxative while also taking antibiotics for infection
    ~ Portions of the laxative binds with the
    antibiotic making absorption more
    difficult
25
Q

Drug Interactions: Excretion Effects

A
  • One drug changes the excretion rate of another drug
  • Ex: one drug occupies the excretion sites at the kidney blocking excretion of the other
26
Q

Adverse Drug Reactions

A
  • Undesirable response from a drug
    ~ Includes drug interactions when the
    result is undesirable
27
Q

Adverse Drug Reactions: Side Effects

A
  • Expected adverse reactions based on the action of the drug
  • Side effects experienced vary due to varied physiology of individuals
    ~ Person may experience a number of
    side effects or none at all
28
Q

Adverse Drug Reactions: Allergic Reactions

A
  • Body reacts to a foreign chemical/inflammatory response
    ~ Majority from antibiotics and non
    steroidal anti-inflammatory drugs
    ~ S&S
    > Minor
    • Itching
    • Swelling
    • Hives
    > Major
    • Bronchospasm (lack of O2 to
    lungs)
    • Anaphylactic Shock (lack of O2
    to organs)
    * Body goes through
    inflammatory response
    causing vasoconstriction
    then vasodilation resulting
    in low BP
29
Q

Adverse Drug Reactions: Organ Cytotoxic Effects

A
  • Drugs has adverse effect in organs especially those involved in metabolism and excretion of drugs
    ~ Liver
    ~ Kidneys
30
Q

Adverse Drug Reactions: Idiosyncratic Reactions

A
  • Reaction that is specific to a person or a specific group of people
    ~ Specific genetics cause people to
    experience reactions not seen in the
    general population
    > Variations in receptors - more or
    less sensitive/more or less in
    number
    > Variations in metabolizing
    enzymes - more or less
    breakdown of the drug
31
Q

Adverse Drug Reactions: Drug-Food/Drug-Herbal Reactions

A
  • Drug interacts with food in the diet
    ~ May increase drug action
    > Antidepressants Vs. Aged Cheese/
    Meats
    ~ May decrease drug action
    > Blood thinners vs. Vitamin K foods

Pathophysiology & Pharmacology (20 decks)

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