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PA 550 > 6/3/25 and 6/6/25 Pharmacokinetics > Flashcards

6/3/25 and 6/6/25 Pharmacokinetics Flashcards

(79 cards)

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1
Q

A drug is a xenobiotic. What is a xenobiotic?

A

A chemical substance foreign to animal life

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2
Q

What are xenobiotics made of?

A

inorganic ions, non peptide organism molecules, small peptide, proteins, nucleic acids, lipids, or carbohydrates

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3
Q

All xenobiotics are optically active. What does this mean?

A

They can rotate the plane of polarized light

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4
Q

What is the size range (weight) of xenobiotics?

A

7 to >50,000 Daltons

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5
Q

Xenobiotics are pharmacologically active. What does this mean?

A

The drug must bind to a receptor to produce pharmacological effects (strong covalent to weaker electrostatic bonds)

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6
Q

What refers to the impact or influence that a compound or drug has on the body or a specific biological target, resulting in a desired therapeutic or physiological response?

A

Pharmacological effect

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7
Q

What processes of the pharmacological effect is involved in pharmacokinetics?

A

Absorption
Distribution
Metabolism
Elimination

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8
Q

What is pharmacokinetics (PK)?

A

What the body does to a drug

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9
Q

What is the role of absorption in PK?

A

Absorption from the side of administration permits entry of the drug (either directly or indirectly) into the plasma (bloodstream).

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10
Q

When is PK steady state reached?

A

When the rate of drug elimination is equal to the rate of drug administration, such that drug levels in the plasma and tissue remains relatively constant

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11
Q

What is drug half-life?

A

the time it takes for the amount of a drug’s active substance in your body to reduce by half

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12
Q

What are 4 factors that influence the rate and extent of drug absorption

A

Bioavailability (F)
Route of administration
Chemical characteristics of drug
Environment where drug gets absorbed

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13
Q

Define bioavailability (F)

A

The fraction or percentage of administered dose that reaches systemic circulation

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14
Q

A drug with good bioavailability

A

F >0.8 (80%)

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15
Q

A drug with bad bioavailability

A

F <0.5 (50%)

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16
Q

What can F be used to calculate?

A

The amount absorbed of a given dose

(F)(Dose)=amount absorbed

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17
Q

What 2 factors can alter the extent of drug absorption (F)?

A

Dosage formulation (tablet vs elixir)
Route of Administration (capsule vs IV)

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18
Q

What is the bioavailability (F) of IV drugs?

A

1.0 (or 100%)

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19
Q

What is the area under the curve (AUC) used to calculate?

A

Used to calculate bioavailability by comparing the plasma concentrations of a drug when given by 2 different routes of administration

Usually compares PO to IV

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20
Q

AUC is plotted using plasma protein concentrations. What the the labels of the curve axis?

A

Time vs Concentration

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21
Q

What does AUC represent

A

The extent of drug absorption

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22
Q

How is bioavailability calculated using AUC?

A

F=(AUC oral/AUC IV)(100)

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23
Q

Will there be a higher peak of concentration with IV or PO drugs?

A

IV

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24
Q

Will there be a more rapid time to peak with IV or PO drugs?

A

IV

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25
Define first-pass hepatic metabolism
Orally administered drugs leave the GI tract and enter the portal circulating for liver metabolism before entering systemic circulation. If the drug is rapidly metabolized by GI bacteria, GI mucosa, or the liver during this initial passage, the amount of unchanged drug entering the systemic circulation is decreased.
26
Does the first-pass effect positively or negatively affect bioavailability?
Negatively
27
Many drugs are either weak acids or bases. What charge do weak acids have?
Typically uncharged/neutral (non-ionized)
28
Many drugs are either weak acids or bases. What charge do weak bases have?
They become ionized, or positively charged, by gaining a proton
29
What drugs pass through biologic membranes more readily?
Nonionized (neutral)
30
If nonionized drugs pass through membranes more readily, what must happen to weak bases before being able to pass?
They must lose a proton to become neutral so it can pass
31
Do hydrophilic or lipophilic drugs more readily absorbed?
Must be largely lipophilic, yet have some solubility in aqueous solutions. Very hydrophilic drugs are unable to cross the lipid rich membrane.
32
What is a drugs formulation based on?
Its chemical properties
33
What formulation of drugs are degraded by enzymes in the GI tract?
Proteins or hormone based drugs
34
How can an oral tablet bypass the stomach degradation process to increase drug absorption in the small intestines?
They have an enteric-coating on them
35
Define the minimum effective concentration.
the minimum plasma concentration of a drug needed to achieve sufficient drug concentration at the receptors to produce the desired pharmacologic response
36
What 2 things help determine the best route of administration of a drug?
Drug properties Therapeutic Objective
37
Where are orally administered drugs primarily absorbed?
Small intestine (high surface area, more blood flow)
38
How can diarrhea affect drug absorption?
Diarrhea can increase motility and decrease absorption
39
How does having food in the stomach affect drug absorption?
Food in the stomach can delay gastric emptying and slow the rate and extent of absorption. A high fat meal can improve absorption of some drugs
40
What affect does calcium have on drug reabsoption?
Calcium in dairy products can decrease the extent of absorption (or bioavailability) or some antibiotics
41
What divalent cations can be chelated?
Fe2+, Mg2+, Ca2+ These are metal ions
42
What is chelation?
a process where a molecule, called a chelating agent, binds to a metal ion, forming a stable ring structure called a chelate. In medicine, this process is used to remove heavy metals from the body by using specific agents that bind to these metals, which are then eliminated through urine
43
Bioequivalence vs Therapeutic equivalence
Bioequivalence focuses on how a drug product is absorbed and becomes available at the site of action. It means two products, typically a generic drug and a brand-name drug, release the active ingredient at similar rates and to a similar extent, exhibiting comparable bioavailability Therapeutic Equivalence is a broader concept that takes bioequivalence into account to ensure a generic drug can be safely substituted for a brand-name drug
44
What affects how well a drug is absorbed through the skin (ointment, gel, patch, cream, microneedles)?
Skin condition (dryness, oily, inflamed), surface area, blood flow, heat and cold, massage
45
What type of patch should not be cut to alter the dose?
Reservoir patch
46
What type of patch can be cut to alter the dose, though it is not necessarily recommended by the manufacturer?
Matrix patch The amount of drug absorbed is dependent on the surface area of the skin
47
What are P-glycoproteins?
Transmembrane proteins responsible for transporting various molecules across membranes
48
What do P-glycoproteins do?
Pump xenobiotics (drugs) out of the cell (from high to low concentration)
49
Areas of high p-glycoprotein expression _____ drug absorption.
Reduce
50
Areas of low p-glycoprotein expression ______ drug absorption.
Increase
51
What is the process by which a drug reversibly leave the bloodstream and enters the interstitial fluid and tissues?
Distribution
52
What are the 2 factors that influence distribution?
Physiologic factors Drug Factors
53
What are examples of physiological factors that influence distribution?
Blood flow and CO Capillary permeability
54
Do organs with more or less blood flow receive the most drug before the other organs and tissues?
More
55
Why is it harder to treat diseases and infections associated with the brain?
The blood-brain barrier has tight gap junctions preventing the entry of many medications
56
What are some drug factors that affect distribution?
Binding of drugs to proteins Lipophilicity Volume of distribution
57
Are drugs binding to protein reversible or irreversible?
Reversible
58
Are drugs bound to proteins active or inactive?
Inactive
59
Drugs need to be in their ____ form to assert their effects.
Need to be in their active, unbound form
60
What is the major drug binding protein?
Albumin
61
Besides binding to proteins, what else can drugs bind do?
Tissue proteins. This leads to accumulation of drug in the tissue, leading to higher drug tissue concentrations compared to extracellular fluid and blood.
62
As free drug concentration decreases due to metabolism and elimination, what happens to the drug that is bound to albumin?
It dissociates from albumin to become free drug in the blood
63
Why is hypoalbuminemia an issue?
If a drug relies on protein binding, but there isn't enough protein present, dosing that patient with a normal dose may cause increased risk of toxicity since there will be more free drug (less protein to bind free drug for temporary inactivation)
64
What are some examples of drugs with clinically significant protein binding?
Warfarin, phenytoin, sulfonamides, ceftriaxone
65
How do lipophilic drugs move across biological membranes?
By dissolving in the lipid membranes and penetrating the cell surface
66
How do hydrophilic drugs penetrate cell membranes?
By passing through slit junctions
67
What is the volume of fluid (L) or size of the apparent space in the body available to contain a drug based on how much is given vs what is found in systemic circulation (plasma)?
Volume of distribution (Vd)
68
If there is a low volume of distribution, what happens to the drug concentration?
Concentration is increased Low volume means less space for drug to spread out/dilute out
69
If there is a high volume of distribution, what happens to the drug concentration?
Concentration is decreased High volume means more space for the drug to spread out/dilute
70
What does the Vd of a drug represent?
The degree to which a drug is distributed in body tissue compared to the plasma Vd=body drug amount (mg)/plasma conc (mg/L)
71
What does it mean if the Vd of a drug >40-50L?
It implies that a drug is bring distributed into tissues or fluids outside the plasma compartment
72
Changes in Vd affects serum concentrations. If Vd is reduced due to dehydration, what happens to the drug concentration?
Increases (less fluid)
73
Changes in Vd affects serum concentrations. If Vd is increased due to edema, what will happen to the drug concentration?
Decrease
74
Define the loading dose
A dosing method for rapidly achieving a therapeutic plasma concentration
75
Loading dose calculation
Loading dose=(Vd*C)/(S*F)
76
How many half lives does it take for a drug to be completely eliminated from the body?
3-5 half-lives
77
When will Vd influence drug concentation?
At the steady state
78
What does an increase in Vd do to a drug's half lfe?
Any factor that increases Vd can increase the half-life of the drug and extend its duration of action.
79
What does the delivery of the drug to organs of elimination depend on?
Blood flow Fraction of drug in plasma

PA 550 (15 decks)

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