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Pharmacology and Nutrition > Pharmacokinetics 1 > Flashcards

Pharmacokinetics 1 Flashcards

1
Q

pharmacokinetics

A

what the body does to drugs

Study of how the body interacts with an administered substance

Branch of pharmacology concerned with the movement of drugs within the body

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2
Q

Clinical pharmacokinetics

A

application of pharmacokinetic principles to the safe and effective therapeutic management of drugs in an individual patient

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3
Q

pharmacodynamics

A

what the drugs do to the body

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4
Q

pharmacokinetics 5 steps

A

1) drug administration =
oral, IV, intraperitoneal, subcutaneous, intramuscular, inhalation

2) absorption and distribution =
membranes of oral cavity, GI, peritoneum, skin, muscles, and lungs

3) binding = target site, inactive storage depots

4) inactivation = liver - primary metabolizer

5) excretion = intestines, kidneys, lungs, sweat glands -> feces, urine, water vapor, sweat, saliva

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5
Q

Stages of Pharmacokinetics:

A

Administration
Absorption
Distribution
Metabolism
Elimination

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6
Q

How the drug is administered does affect the absorption, distribution, metabolism, and elimination =

A

therapeutic response

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7
Q

Routes of Administration

A

Alimentary Canal: Enteral

Nonalimentary Canal: Parenteral

Non-Systemic

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8
Q

Alimentary Canal: Enteral

A

oral
sublingual
rectal (hemorrhoids, constipation)

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9
Q

Nonalimentary Canal: Parenteral

A

Injection
> Intramcuscular
> Subcutaneous
> Intravenous

Transdermal

Inhalation

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10
Q

Non-Systemic

A

Topical
Intranasal
Ocular drops

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11
Q

Trade-Off: Enteral vs Parenteral

A

Enteral routes: fairly simple, easy access but less predictable absorption

Parenteral routes: more difficult, inconvenient but more predictable absorption

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12
Q

Most common enteral administration route is __

A

oral

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13
Q

Enteral: Oral
Advantages =

A

easy method: can self administer

relatively safe: control over large spikes in blood plasma concentration

Most are absorbed in the small intestines: large surface area for absorption

Aqueous meds more bioavailable via rapid absorption vs tablet form

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14
Q

Enteral: Oral
Disadvantages =

A

Drugs must have a relatively high level of lipid solubility to pass through the GI mucosa and into the bloodstream

Large non-lipid soluble molecules pass through the GI and exit via the feces

Encapsulated non-lipid soluble will increase ability to be absorbed

Stomach irritation – pain, discomfort, vomiting

Acidic stomach environment may destroy some compounds before they are absorbed

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15
Q

First pass effect:

A

the concentration of a drug, specifically when administered orally, is greatly reduced before it reaches the systemic circulation

Drug is absorbed by the GI = portal vein = drug metabolized in the liver = target cells

Some of the drug is destroyed during ‘first pass’ in the liver

Dose must be sufficient to pass through liver metabolism, travel to the target cells with concentrations high enough to create a response

First pass effect varies depending on the drug

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16
Q

Amount and rate that drug reaches target cells is less predictable than more direct routes of administration

A

Many factors affect drug absorption in the GI:

> infection
food
rate of gastric emptying
amount of visceral blood flow

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17
Q

First pass metabolism:

A

nasal = drug absorbs directly into veins

heart = pumps blood out to entire body - no delay

oral medications = sit in stomach for 30-45 minutes

venous system = transports blood from nose directly to heart - no liver metabolism

liver = 90% of oral medication is metabolized and destroyed by the liver before it gets to heart

portal circulation = all blood from intestines is taken to the liver for detoxification

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18
Q

Sublingual:

A

drug administered under the tongue, typically a faster route than oral (1-5 min), and more efficient absorption

Example: Nitroglycerin = CAD or previous MI

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19
Q

Buccal:

A

drug administered between the cheek and gums

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20
Q

Drugs absorbed transmucosally -> venous system -> superior vena cava -> right atria

A

Sublingual, buccal, nasal, vaginal, urethral

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21
Q

What happens with the first-pass effect in drugs administered via sublingual or buccal routes?

A

Nitroglycerin can not be taken oral = destroyed by stomach acid

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22
Q

Enteral: Sublingual and Buccal
Advantage:

A

avoid liver metabolism = first pass

Faster effects than oral
> Sublingual/buccal 1-5 minutes vs oral 20-60 minutes

Used with patients who have difficulty swallowing

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23
Q

Enteral: Sublingual and Buccal
Disadvantage:

A

Extended-release drugs do not work well via sublingual or buccal

Eating, drinking, and smoking can affect absorption

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24
Q

Enteral: Rectal

A

Used most often for localized condition

Hemorrhoids = local benefit

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25
Q

Enteral: Rectal
Advantage:

A

Able to administer to an unconscious patient

Used in children

Avoids First Pass Effect

Used in vomiting

Rapid local effects

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26
Q

Enteral: Rectal
Disadvantage:

A

Absorption can be highly irregular = limited surface area

Patient adherence

Irritation of rectal mucosa

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27
Q

Parenteral

A

All routes of administration that do not use the GI are considered parental: injection, inhalation, transdermal

Typically more direct route to the target area

Higher degree of predictability in quantity of drug reaching the target area

Drugs administered via a parenteral route typically not subject to the first-pass effect or stomach acid

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28
Q

Parenteral: Inhalation

A

Drugs in a gaseous or volatile state in an aerosol form

Example: Bronchodilators, steroid inhalers, general anesthesia

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29
Q

Parenteral: Inhalation
Advantages:

A

Large pulmonary surface area for distribution into the pulmonary circulation

Rapid uptake into the bloodstream = 1-2 minutes

Used commonly with bronchial and alveolar conditions

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30
Q

Parenteral: Inhalation
Disadvantage:

A

Irritant to the respiratory tract

Difficult to administer to self = technique

Challenging to predict the amount of a drug that reaches the target tissue

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31
Q

Parenteral: Injections that require absorption

A

Intramuscular = Rapid Absorption

Subcutaneous = Consistent & reliable, good bioavailability

Intravenous = Instantaneous systemic absorption and effect

Intradermal = Local effect

32
Q

Parenteral: Injections that require absorption
Advantage:

A

Good option if oral bioavailability is low

Onset relatively rapid

33
Q

Parenteral: Injections that require absorption
Disadvantages:

A

Risk of infection

Difficult to self-administering

Absorption unpredictable if perfusion poor

34
Q

Injection: Intramuscular (IM)

A

Administered directly to a muscle

Useful for conditions directly associated with the injected muscle

Example: botulinum toxin to treat cerebral palsy spasticity, vaccines

35
Q

Injection: Intramuscular (IM)
Advantages:

A

Relatively steady, prolonged release

Relatively rapid effect

36
Q

Injection: Intramuscular (IM)
Disadvantages:

A

Localized pain and prolonged soreness

Limited use for repeat injections

37
Q

Injection: Subcutaneous (SC)

A

Direct injection beneath the surface of the skin

Used for a local and systemic response

Example: local anesthesia, heparin, and insulin

38
Q

Injection: Subcutaneous (SC)
Advantages:

A

Relatively easy to administer

SC administration allows for a slow release of meds to the systemic circulation

39
Q

Injection: Subcutaneous (SC)
Disadvantages:

A

Absorption unpredictable if poor perfusion = impacts absorption and distribution

Painful injection site

40
Q

Injection: IV

A

Injection of a known quantity of drug into a peripheral vein

Pump or Drip Infusion

IV ‘push’ or bolus

Example: Heparin = anti-coagulant

41
Q

Injection: IV
Advantages:

A

Rapid peak levels in the bloodstream = no absorption phase

Rapid effect on the target tissue

Good choice for emergency situations

Prolonged, steady infusion into the bloodstream for inpatient situations = ease of repeat doses

42
Q

Injection: IV
Disadvantages:

A

Potential adverse reactions due to rapid delivery of large dosage = adverse effects are difficult to manage

43
Q

Parenteral: Transdermal

A

Administered to the surface of the skin with intent that the drug will be absorbed through the dermal layer

Slow, controlled release of a drug with relatively constant blood plasma levels over an extended period of time

Often delivered via a medicated ‘patch’

Examples: nicotine, motion-sickness meds, estrogen and testosterone

44
Q

Two basic properties of transdermals:

A

Must be able to penetrate the skin

Must not be metabolized by enzymes in the skin

45
Q

Examples of ionized medication: Iontophoresis and phonophoresis

A

Electric current or ultrasound waves used to push the ionized form of medication through the dermal layer

Physical therapists use ionto and phono to treat inflammation

Example: Dexamethasone

46
Q

Parenteral: Topical

A

Administered to the surface of the skin or mucus membranes

Used primarily for skin conditions or site of application

47
Q

Parenteral: Topical
Advantage:

A

Application to mucus membranes = Significant amounts of a drug applied can be absorbed

Application to skin = good for localized treatment

Easy, rapid, and convenient way to administer a drug

48
Q

Parenteral: Topical
Disadvantage:

A

Poor absorption through the epidermis into the bloodstream

Examples: antibiotics for cutaneous infections, anti-inflammatory steroids for skin inflammation, eye drops, nasal spray

49
Q

Injection: Intra-Arterial

A

Direct injection into an artery is difficult and dangerous due to rapid availability

Often used with chemotherapy to deliver a drug to a specific site while minimizing exposure to healthy tissue

50
Q

Injection: Intrathecal

A

Administered within a sheath = spinal subarachnoid space

Example: antibiotics to treat meningitis, spinal anesthesia, and pain management

51
Q

Injection: Intrathecal
Advantages =

A

drugs acts directly on meninges and CNS

bypass blood-brain barrier and blood-csf barrier

52
Q

Injection: Intrathecal
Disadvantages =

A

strict aseptic precautions needed

painful procedure

expertise needed

53
Q

Bioavailability

A

The percentage of the medication administered that reaches systemic circulation

100 mg given orally = 50 mg reaches systemic circulation = 50% bioavailable

100 mg given IV = 100 mg in systemic circulation = 100% bioavailable

54
Q

Many factors determine a drugs bioavailability

A

Blood barriers, enzymatic action, liver metabolism, cell membranes, and tissue barriers

Administration Route: Drugs traveling from original point of entry to target tissue will be affected by many factors to determine bioavailability

55
Q

Bioavailability: Membrane Structure and Function

A

Cell membrane structure determines level of permeability to substances

Cell membrane: composed of phospholipids and proteins

Phospholipids are arranged in a bilayer

Hydrophobic tails toward the membrane’s center

Hydrophilic heads away from the center

Protein interspersed amongst the phospholipid bilayer

56
Q

Lipid bilayer acts as a water barrier and impermeable to non-lipid soluble substances

A

Lipid soluble compounds = most drugs are able to pass through the cell membrane by dissolving into the phospholipid bilayer

Channels in the lipid bilayer allow for water and non-lipid soluble compounds to pass through

Drugs can be used to excite these channels to open or close

57
Q

Distribution: Movement Across Membrane Barriers

A

Following absorption

Unmetabolized drug to the site of action

Passive diffusion

58
Q

Passive Diffusion:

A

passage of a drug from one side of a membrane to another given two essential criteria = occurs without expending any energy

59
Q

Gradients =

A

Concentration difference or ‘gradient’: substance moves from an area of high concentration to an area of low concentration

Pressure gradient: substance moves from an area of high pressure to an area of low pressure

60
Q

Membrane permeable to substance that is diffusing

A

Drugs with a high degree of lipid solubility will diffuse readily

Non-lipid soluble drugs are dependent upon channels and active transport

61
Q

Rate of diffusion =

A

dependent upon size of the gradient, size of the diffusing molecule, distance of diffusion, local blood flow, blood brain barrier, and temperature

62
Q

Factors Impacting Absorption & Distribution of Drugs

A

Drugs must first diffuse into the cell via phospholipid bilayer and then out the other side of the cell = tight junctions limit movement around cells

Drugs diffuse across a cell membrane from a region of high concentration (eg, GI fluids) to one of low concentration (eg, blood)

The cell membrane is lipid = lipid-soluble drugs diffuse most rapidly

Small molecules tend to penetrate membranes more rapidly than larger ones

63
Q

Absorption: Water Soluble

A

Osmosis

Water movement from an area of high concentration to an area of low concentration

Cell membrane ‘channels’ or semi-permeable membranes will allow small non-lipid soluble drugs to pass through as water moves from high to low concentration

64
Q

Absorption: Active Transport: Non-Lipid Soluble Substances

A

Use of membrane proteins to transport a substance across the cell membrane

Drugs can utilize active transport systems if the drug resembles some endogenous substance

Example: drugs that resemble amino acids and small peptides will be absorbed in the GI tract via active transport systems that normally absorb AA

65
Q

Effect of Ionization on Lipid Diffusion

A

Drugs diffuse more readily in their natural non-ionized form

Ionization decreases lipid solubility

Most drugs remain in a neutral nonionized form due to neutral fluids in the body

66
Q

Ionization status of a drug changes when:

A

it moves from an environment of similar pH to an environment with a different pH

Example: aspirin is a weak acid -> it stays in a nonionized form in the stomach, this is also an acidic environment -> absorbed readily in the stomach -> when aspirin reaches the small intestines, a basic environment -> it ionizes and is poorly absorbed

67
Q

Ionization =

A

process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions, often in conjunction with other chemical changes

68
Q

Factors that affect drug distribution:

A

Administration Route

Tissue permeability

Blood flow

Binding to Plasma Proteins and Subcellular Components

Blood brain barriers

Fat, muscle

69
Q

Tissue permeability:

A

drugs ability to pass through cell membranes

Lipid soluble drugs can reach all cells

A large non-lipid soluble will remain in the area that it is administered

70
Q

Blood Flow:

A

Drugs circulating in the bloodstream will gain greater access to tissue

71
Q

Binding to Plasma Proteins and Subcellular Components:

A

Some drugs will form a reversible bond to protein in the bloodstream

Some drugs will form bonds within specific cells limiting distribution

Drugs that remain bound will not reach target tissue

72
Q

Blood brain barriers:

A

highly lipid soluble drugs may cross BBB

73
Q

Fat, Muscle:

A

drug accumulation sites

74
Q

Drug Storage

A

Drugs are intended for specific target sites = can be stored temporarily in various tissue and cause adverse effects on storage site tissue

Bone: Storage site for heavy metals (lead) and tetracyclines

Muscle: Drugs enter via passive and active transport, bind with proteins, nucleoproteins, and phospholipids within muscle cells

Organs: Drugs enter via passive and active transport, bind with organ cellular components

75
Q

Adipose Tissue:

A

primary site for drug storage

Tend to have a long storage time due to low metabolic rate and poor blood perfusion

Example: Highly lipid soluble anesthetics

76
Q

Adverse consequences of Drug Storage

A

High concentrations of drugs, drug metabolites, and toxic compounds stored within tissue can cause local damage to the tissue

Liver and kidneys are prone to local damage due to potential high concentrations of drugs

77
Q

Adverse consequences of Drug Storage

example)

A

In a healthy individual, acetaminophen metabolites are inactivated in the liver and excreted by the kidney via the urine

High doses of acetaminophen can cause excessive toxic metabolites that can react with liver proteins = causing liver damage

Pharmacology and Nutrition (5 decks)

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