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NRAD 201D > Exam 2 - Pharmacokinetics > Flashcards

Exam 2 - Pharmacokinetics Flashcards

1
Q

What is bioavailability?

A

The amount of active drug available after it is metabolised in the liver.

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2
Q

What happens to lipophilic medications during distribution?

A

Lipophilic medications tend to accumulate in fat and poorly vascularized tissues, like bone.

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3
Q

What role does the blood-brain barrier play in medication distribution?

A

The blood-brain barrier blocks most medications from entering brain tissues, except for fat-soluble and low-polarity medications.

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4
Q

How does the lipid composition of cell membranes affect medication distribution?

A

Fat-soluble molecules cross cell membranes faster due to the lipophilic nature and phospholipid composition of the membrane.

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5
Q

How does body fat percentage affect medication distribution?

A

Fat deposits retain lipid-soluble medications and release them over time, leading to prolonged pharmacological effects in obese patients.

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6
Q

How do factors like disease and injury affect medication distribution?

A

Inflammation, disease, and injuries like burns can increase capillary permeability, altering protein binding and allowing more free medication to reach tissues.

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7
Q

Where does drug metabolism mainly take place?

A

In the liver.

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8
Q

Where does drug excretion mainly take place?

A

In the kidneys.

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9
Q

How quickly do drugs reach general circulation when injected?

A

Drugs reach general circulation quickly and have an immediate effect.

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10
Q

What is the first-pass effect?

A

The metabolism of a drug by the liver before it enters general circulation.

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11
Q

Which vein carries orally administered drugs to the liver?

A

The hepatic portal vein.

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12
Q

What is the role of hepatic microsomal enzymes, such as p450, in drug metabolism?

A

They convert lipophilic drugs into hydrophilic compounds for excretion.

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13
Q

What is enzyme induction in drug metabolism?

A

The process where repeated use of certain drugs increases the amount of metabolic enzymes, thereby increasing drug metabolism.

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14
Q

What is enzyme inhibition in drug metabolism?

A

When certain drugs compete to bind to metabolic enzymes, decreasing drug metabolism.

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15
Q

How does an increased metabolic rate affect a drug’s duration and intensity of effect?

A

It decreases the drug’s duration and intensity by facilitating excretion.

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16
Q

How does a decreased metabolic rate affect a drug’s duration and intensity of effect?

A

It increases the drug’s duration and intensity.

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17
Q

What are some other routes of drug excretion besides the kidneys?

A

Excretion through breast milk (in lactating women), exhalation through the lungs, release into bile, and elimination through saliva and sweat.

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18
Q

what is Pharmacotherapy?

A

use of drugs to prevent or treat diseases

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19
Q

2 types of drug classifications

A

Therapeutic
pharmacologic

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20
Q

Therapeutic Classification

A

overall treatment category
Antibiotics, antidiabetics, antihypertensive

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21
Q

Pharmacologic classification

A

how is treats at site of action
calcium channel blocker, ACE inhibitor, beta-blocker

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22
Q

What is Pharmacology?

A

the study or science of drugs

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23
Q

What is Pharmaceutics?

A
  • preparing and dispensing drugs
  • includes dosage form design
    — form determines rate of drug dissolution and absorption
    — Example: liquid absorbed faster than tablets
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24
Q

Abbreviations indicating prolonged TE

A

CR: controlled release
SA: sustained action
XL: extended length
XT: extra time
CD: controlled delivery
TR: time release
ER: Extended release
LA: long acting

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25
Q

Considerations for extended release drugs

A
  • release of drug molecules over a prolonged period
  • prolongs drug absorption 8-24 hours
  • requires fewer doses, improved compliance
  • cannot be crushed or chewed → possible toxicity
    — Long dose delivered all at once
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26
Q

Types of oral drug preparations from fastest to slowest

A
  • Buccal (side of cheek) & sublingual {SL)
  • Liquids & syrups
  • Capsules
  • Tablets
  • Enteric Coated tablets
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27
Q

Where do enteric coated tablets dissolve?

A

Dissolve in small intestine d/t alkaline environment

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28
Q

What is Pharmacokinetics?

A
  • “kinetics” = movement
  • study of the drug movement throughout the body
  • 4 processes (ADME)
    — Absorption: how does it get in?
    — Distribution: where will it go?
    — Metabolism: how is it broken down?
    — Excretion: how does it leave?
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29
Q

ADME: Absorption

A
  • rate affected by route
  • oral medications undergo first-pass effect
  • Enteric absorption can occur in stomach and/or small intestine
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30
Q

What affects absorption?

A

Absorption affected by
- acidity
- food (presence or absence)
- age
- others
- Gastrectomy = reduced surface area

31
Q

Routes of administration

A
  • Enteral
  • Parenteral
  • Topical
32
Q

What are first pass enteral routes?

A

– oral, GI tract (mouth to rectum)
– first pass metabolism
– less than 100% available

33
Q

What are non-first pass enteral routes?

A
  • orally disintegrating tablets (ODTs)
  • oral soluble films
  • Sublingual & buccal (transmucosal)
34
Q

How do non-first pass enteral drugs get absorbed?

A
  • oral cavity highly vascularized
  • do not undergo first-pass effects: direct to bloodstream

Ex: zofran
Saliva doesn’t count

35
Q

First Pass Routes

A
  • Oral
  • Rectal
36
Q

Non-First Pass Routes

A
  • Inhaled
  • IV
  • Sublingual
  • Intranasal
  • IM
  • Subcutaneous
  • Transdermal patches
37
Q

How are rectal drugs distributed?

A
  • used for both local and systemic delivery
  • may be considered enteral or topical
  • mixed first-pass and non-first-pass absorption and metabolism

ex: Rectal acetaminophen
— Reduces fever = systemic

ex: Rectal dulcolax
— Stimulates BM = local

38
Q

What is Parenteral route?

A

– IM, IV, subcutaneous
– avoid first pass
– IV is only 100% available option

39
Q

What is Topical route?

A

– ointments, gels, patches, drops, inhalers
– some avoid first pass

40
Q

ADME: Distribution

A

transport of drug from bloodstream to

  1. Most metabolically active organs first = more blood flow
    - heart
    - liver
    - kidneys
    - brain
  2. Less metabolically active second
    - muscle
    - skin
    - fat
  • once in the bloodstream, elimination starts
    — primarily liver and kidneys
41
Q

What happens to unbound drug molecules?

A
  • unbound drugs free to distribute and reach site
  • Pass through membrane to target tissue
  • More unbound = greater rate of elimination
42
Q

How does protein binding affect distribution?

A
  • drugs bound to plasma proteins are pharmacologically inactive
  • Cannot get through membrane to reach target tissue
  • binding reduces onset time
  • extends duration & elimination

ex: Warfarin needs to be bound to proteins
- 99% bound to albumin
- 1% free

Onset 36-72 hours
Elimination (duration) 2-5 days

43
Q

What are Factors that may affect protein binding?

A
  • How much protein is in your system
  • Nutrition, age, liver failure
    — Liver produces proteins
  • Other drugs using up protein for their binding = competing for binding sites
    — High affinity gets first pick. Bound proteins will be displaced.
44
Q

What happens when a drug can’t bind its protein?

A
  • Drugs that can’t bind when they should = toxicity
45
Q

ADME: Metabolism

A
  • Liver is mostly responsible for drug metabolism (enzyme activity)
  • Most common liver enzyme = P450
    — Lipid → water solubility
    — Goal is water solubility so that kidney can filter out inactive metabolite
46
Q

Biotransformation

A
  • chemical alteration of drugs –> more easily excreted from the body.
  • occur primarily in the liver
    1. reduces number of active drug molecules /or/
    2. activates drug
    — (prodrug) Designed to be activated in the liver
    — Think prohormone
47
Q

Consequence of slow metabolism

A
  • TE lasts longer
  • Onset and duration prolonged
  • Working slower, staying longer
  • Toxicity is concern
48
Q

How does age affect metabolism?

A
  • Low HCl-
  • Less muscle = slower metabolism
  • Higher fat
  • Less liver enzymes
49
Q

ADME: Excretion

A
  • kidneys primarily responsible
  • small fraction excreted in original compound
  • Some excretion through stool
50
Q

What could affect excretion?

A
  • Kidney disease/failure
  • Higher risk of toxicity b/c drug in system longer
  • Dialysis = possible intervention
51
Q

Why is knowing about first-pass effect and bioavailability important?

A
  • First pass reduces therapeutic effect
    — slows the action time.
    — If pt needs action immediately, med should go directly to the blood
  • The first-pass effect can significantly reduce the oral bioavailability
  • can also cause high inter-patient variability
    — variation in the expression and activity levels of metabolizing enzymes
52
Q

Transdermal Patches Distribution

A

Fentanyl
- Location doesn’t matter.
- Systemic effect
- Slow onset → long duration

OTC pain patch
- Place on painful area
- Local anesthetic

53
Q

Onset of action

A

time for drug to start physiologic response

54
Q

Peak effect

A

Time required for drug to reach max therapeutic response

55
Q

Duration of action

A

length of time drug concentration is sufficient to elicit therapeutic response

56
Q

Half-life

A
  • time required for 50% of drug to be removed by the body

Ex: 100mg with 12 hr half life
100 mg → 12 hr = 50 mg → 12 hr = 25 mg → 12 hr = 12.5 mg…

57
Q

Steady State

A

(reach steady state): 50% in blood, 50% eliminated
- Should wake patients to administer meds to keep up with elimination, maintains steady state of TE
- It takes four to five doses of a regularly scheduled drug to reach a steady state, depending on the drug’s half life.
- This is important because the steady state concentration of a drug is necessary for adequate symptom management

58
Q

Pharmacodynamics

A

drug-induced physiological changes

59
Q

Mechanism of action

A
  • effect based on characteristics of cells/tissue targeted by the drug
  • Drugs exert action via receptors, enzymes, and non-selective interactions
60
Q

Affinity

A

Physiologic response based on “fit” to receptor

61
Q

Receptor site bonding types

A

Drugs act by forming chemical bonds with specific receptor sites
- Agonist: best fit = best response (TE)
- Antagonist = block receptors
— Ex: narcan blocks receptor for morphine binding
— Also displaces bound morphine
Partial agonist: diminished response

62
Q

Leafy green veg interaction with warfarin

A

Leafy green veggies (K) → warfarin
↑ intake of leafy green veggies may ↓ anticoagulant effect
K stim clotting

63
Q

Grapefruit juice interaction with drugs

A
  • Grapefruit juice → cardiac medications, anti-seizure, anti-cholesterol, anti-anxiety
  • Cause problems with liver enzymes and transporters
  • Too much or little drug
64
Q

Valerian root interaction with drugs

A

Valerian root → CNS depressants
- Can increase drowsiness and sedation
- Stim sleep

65
Q

Polypharmacy

A
  • “many drugs”
  • Rx and OTC (ie., dietary supplements)
  • longer lifespans and aging baby boomers
    — longevity ↑ need for medications
  • greater the possibility of experiencing AEs and drug interactions
    — Ex: diuretic with beta blocker → risk of hypOtension
66
Q

Aging Effects On Pharmacokinetics

A

CV, GI, Hepatic, Renal all affect excretion → toxicity risk

67
Q

Age and CV

A

Reduced output = reduced absorption and distribution

68
Q

Age and GI

A

Increased pH → alkaline secretions = altered absorption
Reduced peristalsis → delayed gastric emptying

69
Q

Age and Hepatic

A

Less enzyme production = less metabolism
Less blood flow = less metabolism

70
Q

Age and renal

A

Low blood flow = low excretion
Low function = low excretion
Low GFR = low excretion

71
Q

Dosing Variations For The Elderly

A
  • ½ to ⅔ of standard adult dose
  • Dose is range: “Start low and go slow”
  • Increase dose based on response
  • Look at geriatric dosing recommendations in drug guide before administering
72
Q

Ethnic & Cultural Factors Influence On Pharmacotherapy
- Medication beliefs

A
  • Question need for medications
  • Beliefs about disease and self-management approach
  • Influences by culture, family experiences, and individual preferences
  • Mistrust of HCP –> lower medication adherence
73
Q

Ethnic & Cultural Factors Influence On Pharmacotherapy
Medication beliefs
- Language barriers to adherence

A
  • Limited English proficiency
  • HCP may spend less time if interpreters not available
  • Miscommunication issues and poor follow-through
74
Q

Ethnic & Cultural Factors Influence On Pharmacotherapy
- Complementary and Alternative Medications (CAM)

A
  • Used with prescribed medication or as an alternative
  • Use of natural products
  • Mind and body practices: yoga, meditation, prayer…
  • More economical than prescribed medications

NRAD 201D (3 decks)

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