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Pharm 1 Exam 1 > Principles of Drug Action > Flashcards

Principles of Drug Action Flashcards

1
Q

What is pharmokinetics?

A

The study of drug movement throughout the body.

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2
Q

What should we know about pharmokinetics?

A
  • How the body deals with medication
  • Understand & predict actions, side effects of medications
  • Understand obstacles a drug faces to reach target cells
  • Greatest barrier for drugs is crossing many membranes
  • Enteral route drugs are broken down by stomach acids and digestive enzymes
  • Organs attempt to excrete medicines
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3
Q

What are the four categories of pharmacokinetic processes?

A
  • Absorption
  • Distribution
  • Metabolism
  • Excretion
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4
Q

What are factors affecting drug absorption?

A
  • Dose
  • Route of administration
  • Size of the drug molecule
  • Surface area of the absorptive site
  • Digestive motility
  • Blood flow
  • Lipid solubility of the drug
  • pH of local environment
  • Drug-Drug/Food-Drug interactions
  • Dietary supplement/herbal product-drug interactions
  • Food
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5
Q

What is bioavailability?

A

% of the drug that reaches the circulation.

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6
Q

What is the primary pharmacokinetic factor that determines length of time for drug to produce effect?

A

Absorption

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7
Q

What is distribution in pharmacokinetics?

A

Transport of drugs throughout the body

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8
Q

What is the simplest factor determining distribution is the amount of blood flow to body tissues??

A

Distribution

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9
Q

What are some factors of distribution?

A

*Physical properties of drug have great influence
* Tissue affinity
* Protein binding

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10
Q

What role does the Blood-brain barrier and Fetal-placenta barrier have in distribution?

A
  • Special anatomic barriers that prevent many chemicals and medications from entering.
  • Make brain tumors difficult to treat
  • Fetal-placenta barrier protects fetus; no pregnant woman should be given medication without strong consideration of condition.
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11
Q

What is biotransformation?

A

The metabolism of medications
* Chemically converts drug so it can be easily removed from body
* Involves complex biochemical reactions
* Liver - primary site
* Addition of side chains, known as conjugates, makes drugs more water soluble and more easily excreted by the kidneys.

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12
Q

What is Half-life of drugs?

A
  • Time it takes for half of the medication to be metabolized by the liver.
  • The greater the half-life, the longer it takes to excrete
  • Determines frequency and dosage
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13
Q

What is the first pass affect?

A
  • Drug is absorbed
  • Drug enters hepatic circulation, goes to liver
  • Drug is metabolized to inactive form
  • Drug conjugates and leaves liver
  • Drug is distributed to general circulation
  • Many drugs are rendered inactive by first-pass effect.
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14
Q

What is the process of enterohepatic-recirculation of Drugs - Second pass effect?

A
  • Drugs are excreted in bile
  • Ble recirculates to liver
  • Percentage of drug may be recirculated numerous times
  • Prolongs activity of drug
    —— Activity of drug may last after discontinuation
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15
Q

What are some factors in excretion of medications?

A
  • Primary site of excretion of drugs is kidneys
  • Free drugs, water-soluble agents, electrolytes, and small molecules are easily filtered.
  • Drug-protein complexes and large substances are secreted into distal tubule of nephron
  • Secretion mechanism is less active in infants and older adults
  • pH of filtrate can increase excretion
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16
Q

What does renal failure have on excretion of medications?

A
  • Drugs are retiained for extended times
  • Dosages must be reduces
17
Q

What other organs are sites for excretion?

A
  • Respiratory system
  • Glands
  • Biliary system
18
Q

What is drug plasma concentration and therapeutic response?

A
  • Concentration of medication at target tissue is often impossible to measure, so it must be measured in plasma.
    —— Minimum effect concentration - amount of drug required to produce a therapeutic effect.
    —— Toxic concentration - level of drug that will result in serious adverse effects.
    —— Therapeutic range - Plasma drug concentration between the minimum effective concentration and the toxic concentration.
19
Q

How do drugs reach and maintain therapeutic range?

A
  • Repeated doses of drug are given
  • Drug accumulates in bloodstream
  • Plateau is reached
  • Amount administered equals amount eliminated
20
Q

What is a loading dose?

A
  • Higher amount of drug given
  • Plateau reached faster
  • Quickly produces therapeutic response
21
Q

What is median lethal dose?

A
  • Used to assess safety of a drug
  • Shown on frequency distribution curves
  • Determined in preclinical trials
  • Is lethal dose in 50% of group of animals
  • Cannot be experimentally determined in humans
22
Q

What is the median toxicity dose?

A
  • Dose that will produce given toxicity in 50% of group of patients
  • Value may be extrapolated from
    —— Animal data
    —— Adverse effects in patient clinical trials
  • Needed because median lethal dose cannot be tested in humans
23
Q

What happens when drugs attach to receptors?

A
  • May trigger second messenger events
    —— E.g. activation of specific G proteins and associated enzymes
  • Initiates drug action
  • Can stimulate or inhibit normal activity
24
Q

What happens with drugs that act as agonists?

A
  • Bind to receptor to create a response
  • Produce same response as endogenous chemical
  • Sometimes produce greater maximal response
25
Q

What happens when a drug acts as a partial agonist?

A
  • Bind to receptor - partial
  • Produce weaker, less effective response than agonists
26
Q

What happens when a drug acts as an antagonist?

A
  • Block receptor to block response
  • Prevent endogenous chemical from acting
  • Often compete with agonists for receptor
27
Q

Specific vs Nonspecific cellular responses?

A
  • Nonspecific
    —— Affect whole body
    —— Create more side effects
  • Specific
    —— Affect target tissue
    —— Less side effects
28
Q

What is customized drug therapy?

A
  • End of single-drug, one-size-fits-all policy
  • DNA test before receiving drug
  • Prevention of idiosyncratic (unpredictable and unexplained) drug reactions
  • Pharmacogenetics
29
Q

What is pharmacogenetics?

A

Area of pharmacology that examines role of heredity in drug response.

30
Q

What other factors play a role in pharmacotherapy?

A
  • Tolerance
  • Serum drug levels
  • Kidney function
31
Q

Wat needs to be monitored in the kidneys?

A
  • BUN (blood urea nitrogen)
  • Creatinine
  • Creatinine clearance rate

Pharm 1 Exam 1 (4 decks)

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