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Pharmacology and Nutrition > Pharmacokinetics 1 > Flashcards

Pharmacokinetics 1 Flashcards

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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
Enteral: Rectal Advantage:
Able to administer to an unconscious patient Used in children Avoids First Pass Effect Used in vomiting Rapid local effects
26
Enteral: Rectal Disadvantage:
Absorption can be highly irregular = limited surface area Patient adherence Irritation of rectal mucosa
27
Parenteral
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
28
Parenteral: Inhalation
Drugs in a gaseous or volatile state in an aerosol form Example: Bronchodilators, steroid inhalers, general anesthesia
29
Parenteral: Inhalation Advantages:
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
30
Parenteral: Inhalation Disadvantage:
Irritant to the respiratory tract Difficult to administer to self = technique Challenging to predict the amount of a drug that reaches the target tissue
31
Parenteral: Injections that require absorption
Intramuscular = Rapid Absorption Subcutaneous = Consistent & reliable, good bioavailability Intravenous = Instantaneous systemic absorption and effect Intradermal = Local effect
32
Parenteral: Injections that require absorption Advantage:
Good option if oral bioavailability is low Onset relatively rapid
33
Parenteral: Injections that require absorption Disadvantages:
Risk of infection Difficult to self-administering Absorption unpredictable if perfusion poor
34
Injection: Intramuscular (IM)
Administered directly to a muscle Useful for conditions directly associated with the injected muscle Example: botulinum toxin to treat cerebral palsy spasticity, vaccines
35
Injection: Intramuscular (IM) Advantages:
Relatively steady, prolonged release Relatively rapid effect
36
Injection: Intramuscular (IM) Disadvantages:
Localized pain and prolonged soreness Limited use for repeat injections
37
Injection: Subcutaneous (SC)
Direct injection beneath the surface of the skin Used for a local and systemic response Example: local anesthesia, heparin, and insulin
38
Injection: Subcutaneous (SC) Advantages:
Relatively easy to administer SC administration allows for a slow release of meds to the systemic circulation
39
Injection: Subcutaneous (SC) Disadvantages:
Absorption unpredictable if poor perfusion = impacts absorption and distribution Painful injection site
40
Injection: IV
Injection of a known quantity of drug into a peripheral vein Pump or Drip Infusion IV ‘push’ or bolus Example: Heparin = anti-coagulant
41
Injection: IV Advantages:
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
Injection: IV Disadvantages:
Potential adverse reactions due to rapid delivery of large dosage = adverse effects are difficult to manage
43
Parenteral: Transdermal
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
Two basic properties of transdermals:
Must be able to penetrate the skin Must not be metabolized by enzymes in the skin
45
Examples of ionized medication: Iontophoresis and phonophoresis
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
Parenteral: Topical
Administered to the surface of the skin or mucus membranes Used primarily for skin conditions or site of application
47
Parenteral: Topical Advantage:
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
Parenteral: Topical Disadvantage:
Poor absorption through the epidermis into the bloodstream Examples: antibiotics for cutaneous infections, anti-inflammatory steroids for skin inflammation, eye drops, nasal spray
49
Injection: Intra-Arterial
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
Injection: Intrathecal
Administered within a sheath = spinal subarachnoid space Example: antibiotics to treat meningitis, spinal anesthesia, and pain management
51
Injection: Intrathecal Advantages =
drugs acts directly on meninges and CNS bypass blood-brain barrier and blood-csf barrier
52
Injection: Intrathecal Disadvantages =
strict aseptic precautions needed painful procedure expertise needed
53
Bioavailability
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
Many factors determine a drugs bioavailability
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
Bioavailability: Membrane Structure and Function
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
Lipid bilayer acts as a water barrier and impermeable to non-lipid soluble substances
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
Distribution: Movement Across Membrane Barriers
Following absorption Unmetabolized drug to the site of action Passive diffusion
58
Passive Diffusion:
passage of a drug from one side of a membrane to another given two essential criteria = occurs without expending any energy
59
Gradients =
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
Membrane permeable to substance that is diffusing
Drugs with a high degree of lipid solubility will diffuse readily Non-lipid soluble drugs are dependent upon channels and active transport
61
Rate of diffusion =
dependent upon size of the gradient, size of the diffusing molecule, distance of diffusion, local blood flow, blood brain barrier, and temperature
62
Factors Impacting Absorption & Distribution of Drugs
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
Absorption: Water Soluble
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
Absorption: Active Transport: Non-Lipid Soluble Substances
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
Effect of Ionization on Lipid Diffusion
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
Ionization status of a drug changes when:
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
Ionization =
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
Factors that affect drug distribution:
Administration Route Tissue permeability Blood flow Binding to Plasma Proteins and Subcellular Components Blood brain barriers Fat, muscle
69
Tissue permeability:
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
Blood Flow:
Drugs circulating in the bloodstream will gain greater access to tissue
71
Binding to Plasma Proteins and Subcellular Components:
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
Blood brain barriers:
highly lipid soluble drugs may cross BBB
73
Fat, Muscle:
drug accumulation sites
74
Drug Storage
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
Adipose Tissue:
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
Adverse consequences of Drug Storage
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
Adverse consequences of Drug Storage example)
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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