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PHA 3112 > 1.1 - Pharmacokinetics > Flashcards

1.1 - Pharmacokinetics Flashcards

Material covered in midterm #1

1
Q

What kinds of things are considered drugs by the FDA?

A

Pharmaceuticals
Biologics
Disinfectants
Natural Health Products (Vitamins, minerals, herbal products)

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2
Q

Pharmacology initially evolved from which other sciences?

A

Botanists, who studied plants and natural materials.
Chemists, who later attempted to extract and purify these natural materials.
Gradual advancements in both chemistry and physiology allowed for a scientific explanation of how drugs act on the body.

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3
Q

How long is a trade name able to patent the drug after discovering it?

A

20 years.

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4
Q

What is the generic name for ventolin?

A

Salbutamol

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5
Q

What is a subsequent entry drug?

A

Another name for a generic drug that produces it, but did not discover or patent it.

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6
Q

What are pharmacokinetics?

A

The study of what the body does to a drug

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7
Q

What are pharmacodynamics?

A

The study of what a drug does to the body

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8
Q

What are some examples of surface drug administration?

A

Topical, ophthalmic, vaginal, transdermal

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9
Q

What are some examples of enteral drug administration?

A

PO, SL, PR

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10
Q

What are some examples of parenteral drug administration?

A

IM, SC, IV, IA

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11
Q

What does the abbreviation ad lib. mean?

A

As much as desired, freely

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12
Q

What does the abbreviation PR mean?

A

Rectally

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13
Q

What does the abbreviation PV mean?

A

Vaginally

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14
Q

What kind of medication route are nasal sprays, vaginal application, or eyedrops?

A

Topical administrations

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15
Q

What is the difference between a cream and an ointment?

A

Ointment is oily and stays on the skin, whereas a cream will rub into the skin.

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16
Q

What is transdermal administration? Give some examples.

A

Something absorbed gradually through intact skin, with variable absorption depending on lipid solubility and blood flow to area of application.
e.g., hormone, nicotine, fentanyl, nitroglycerine patches.

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17
Q

What differentiates topical vs transdermal administration?

A

Transdermal is released gradually and continuously (and enters blood), and topical is applied directly to the area it must act.

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18
Q

Why might transdermal administration be dangerous?

A

It can often be unpredictable, and this can be dangerous with narcotics administered in small doses - such as fentanyl.

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19
Q

What kind of drug administration can bypass the liver?

A

Sublingual administration drains directly into the vena cava - bypasses hepatic portal.

Some rectal BVs also bypass the portal, but usually this is not the main reason for rectal administration.

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20
Q

How is nitroglycerine given (route)?

A

Many ways, but never PO because it will be destroyed by the liver. Most common is SL

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21
Q

What are exipients?

A

Non-active ingredients in a tablet/capsule

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22
Q

How much liquid should a pill be taken with?

A

At least 100 mL

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23
Q

What is an emulsion?

A

Mix of water/oil

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24
Q

What is a suspension?

A

When an insoluble matter in water is suspended - mix before dispensing

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25
Q

What is a tincture or elixir?

A

Alcohol-based extraction of active components from plants.

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26
Q

What is enteral administration of a drug?

A

GI administration (PO, SL, Bucco-gingival, PR)

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27
Q

What is first pass metabolism?

A

Is the drug being transformed when it first enters the body through the liver
i.e., nitroglycerine has a high first pass hepatic metabolism

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28
Q

What is the most direct route of drug administration?

A

IV - also most dangerous because it requires extra vigilance or aseptic technique and appropriate dosing

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29
Q

What is phlebitis?

A

Swelling of the blood vessel following IV administration - usually caused by medication itself.

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30
Q

What routes of medication administration are considered parenteral?

A

SC, IM, IV, IA, Implant,

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31
Q

When would intraosseous administration be used?

A

Used in resuscitation of critically ill adults or peds pts if rapid a timely peripheral IV cannot be established or has failed.

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32
Q

What is the onset of action?

A

The time after drug administration before it has reaches the minimum effective concentration threshold

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33
Q

What is tmax?

A

The time is takes for an administered drug to reach its maximum concentration

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34
Q

What are the ADMEs of pharacokinetics?

A

Absorption, Distribution, Metabolism, Elimination
(Not necessarily in that order)

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35
Q

What is Bioavailability (F)?

A

The fraction of unchanged drug that reaches the systemic circulation (Ideally, it would be 100%)

F = 100% means all drug administered has reaches the systemic circulation (IV)
F < 100% if some drug was lost before reaching the heart

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36
Q

What kinds of things might affect the bioavailability of a drug?

A

–> Route
–> Loss before intestinal absorption
–> Lost by modification of the drug or hepatic metabolism
–> Lost because transporters return the it to the GI tract (stuck in bile, or returned to small intestine)

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37
Q

Which letter (ADME) of pharmacokinetics is affected by bioavailability (F)?

A

A - Absorption
Bioavailability is the fraction of drug administered that makes is to systemic circulation

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38
Q

What is area under the curve?

A

The bioavailability of a drug compared to when it is administered IV (if the AUC of oral admin is half the size of IV admin, then is has an oral bioavailability of 50%)

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39
Q

How does medication dose size affect the area under the curve?

A

The higher the dose, the larger the area

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40
Q

How is area under the curve impacted by kidney disease?

A

Kidney disease decreases elimination rate, therefore there will be a larger area under the curve for these individuals.

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41
Q

What factors affect the area under the curve of drug administration?

A

—> Bioavailability
–> Dose of drug
–> Clearance rate

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42
Q

How does the rate of gastric emptying impact bioavailability of PO drugs?

A

If emptying is slow, bioavailability is reduced

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43
Q

How does intestinal emptying impact bioavailability?

A

If the rate is fast it decreases bioavailability.
If the rate is slow, theoretically it could improve bioavailability.

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44
Q

How does GI surface area impact bioavailability?

A

Decreased surface area due to inflammation (Chron’s, Celiac) or surgical resection both reduce bioavailability

45
Q

How does severe liver disease impact bioavailability?

A

Severe liver disease would increase bioavailability

46
Q

How does pH affect bioavailability?

A

It can affect the drug’s charge (as most drugs are weak acids or bases, and change depending on pH)

Charge of a drug determines whether or not it can cross the plasma membrane

47
Q

In what pH are weak acids better absorbed?

A

A weak acid in an acidic solution will be in HA form - not charged. It will more easily pass through the cell membrane, and will be easier to absorb.

HA <–> H+ and A-

48
Q

In what pH do weak acids absorb poorly?

A

In an alkaline solution, the drug will dissociate into H+ and A- form, meaning that it cannot cross cell membranes and will be harder to absorb.
HA <–> H+ and A-

49
Q

In what pH are weak bases better absorbed?

A

In an alkaline solution, most of the drug will be in B form. B is not charged, and can therefore more easily cross the cell membrane, and the drug will be better absorbed.
BH+ <–> H+ and B

50
Q

In what pH are weak bases poorly absorbed?

A

In an acidic solution, the drug will be in its BH+ form. Because it is charged it will not be able to diffuse passively through the cell membrane. Therefore, the drug will not be absorbed as well.
BH+ <–> H+ and B

51
Q

What happens to ciprofloxacin when it interacts with antacids?

A

It forms a precipitation

52
Q

Tetracycline forms a precipitation when interacting with calcium. What implications does this have?

A

It cannot be administered intraosseous or to pregnant individuals.
It also means that people should not eat calcium rich foods and take the medication at the same time.

53
Q

How can you avoid potential interactions with food between medications?

A

Wait 1 hour before eating after taking medications
OR
Wait 2-3 hours after meals to take medication

54
Q

What is the word for when a tablet turns into granules? What about when granules become fine particles?

A

Disintegration –> Deaggregation

55
Q

In what form will PO drugs dissolve the fastest?

A

Dissolution occurs fastest when the tablet is in its smallest form (with the most surface area)

56
Q

Which tissues are very well perfused and therefore have rapid distribution of drugs in systemic circulation?

A

Kidney, liver, heart, lungs, brain

57
Q

What kinds of tissues are the least perfused and therefor have slower distribution of drugs in systemic circulation?

A

Adipose tissue, skin, bone.
e.g., oral antibiotics don’t work that well for tooth infections because the tooth is not very well perfused.

58
Q

What is the formula for volume of distribution?

A

Vd = amount of drug in the body / plasma concentration

59
Q

What is volume of distribution?

A

The volume of the pool of available bodily liquid (and tissue) required to account for observed drug concentration initially measured in the body.

60
Q

How is the average dose of a drug determined?

A

Dose = Therapeutic concentration x volume of distribution

61
Q

What kind of affinity and capacity do plasma proteins have for drugs?

A

Low affinity and high capacity
–> Protein (usually albumin) easily lets go of the drug, and has a high capacity for carrying it.

62
Q

How does being bound to a plasma protein affect a drug’s ability to move across BVs?

A

Being bound to plasma proteins prevents the drug from leaving blood vessels, cross membranes, bind to receptors, and being excreted by the kidneys.

63
Q

Does a drug that is highly bound (99%) to plasma proteins necessarily demonstrate low pharmacological activity?

A

no, even if 99% of a drug is bound and inactive,1% is free and active. That is enough for the drug to be able to interact with its receptor and have an effect on its target.

64
Q

Drug to drug interactions that affect binding of plasma proteins of other drugs can be clinically relevant if:

A
  1. The initial drug is highly bound to plasma proteins (80%)
  2. The therapeutic index of the bound drug is narrow (dangerous)
  3. The effectiveness of elimination systems is reduced (Kidney injury)
65
Q

What is the therapeutic index?

A

The difference between a therapeutically effective dose and a toxic one.

66
Q

Why is it a problem if a drug (like warfarin) goes from bring 99% bound to plasma proteins to 98% bound to plasma proteins?

A

The dose of free drug in the system has now doubled

67
Q

How is the therapeutic index of a drug decided?

A

It is a ratio comparing the lethal or toxic dose of 50% of the population (LD50), to the dose that is effective to 50% of the the population (TD50)

50% of the dose is important because people’s physiological response to a drug (and what is considered a lethal/therapeutic dose) occurs on a bell curve.

68
Q

Drugs can selectively accumulate in tissues such as bone, liver, adipose tissue, etc.
If tissue binding it high, then Vd will be…

A

higher

69
Q

If binding to plasma proteins is high, then Vd will be…

A

high

70
Q

All the water in the body makes up what percentage of the body weight?

A

60%

71
Q

Where does tetracycline accumulate?

A

In the bone

72
Q

Give an example of a drug that accumulates in a bone:

A

Tetracycline

73
Q

Where does chloroquine accumulate?

A

in the liver

74
Q

Where do insecticides accumulate?

A

In adipose tissue

75
Q

Give an example of a drug that accumulates in a adipose tissue:

A

Insecticides

76
Q

Give an example of a drug that accumulates the liver:

A

Chloroquine

77
Q

What is the most important way drugs get into cells?

A

Through passive diffusion, which requires liposolubility (uncharged)

78
Q

What is the second most important way drugs pass through the cell memrane?

A

Through Protein-Assisted Transport
(either facilitated diffusion, or primary or secondary active transport)

79
Q

What is the difference between protein assisted transport and passive transport?

A

Protein assisted diffusion can become saturated, limiting he amount of a molecule that can pass at a specific rate.

80
Q

What is the only way a charged molecule can make it to the brain?

A

Through specialized transport proteins, such as p-glycoproteins because the BBB has tight junctions between BVs and no gaps that occur elsewhere.

81
Q

Many phase I reactions are catalyzed by members of the ___ enzyme family

A

Cytochrome P450 family.

82
Q

If a pt is taking a medication that is normally broken down by 1A2 but is a smoker, how will that affect the amount of the drug in their system?

A

There will be less drug in the system, because cigarette smoke induces 1A2 activity.

83
Q

In what form will a drug be most easily excreted?

A

In charged form, because when uncharged it can diffuse (be reabsorbed) back into systemic circulation.

84
Q

What is half life? What kinds of things affect it?

A

The amount of time is takes for the plasma concentration of a drug to decrease by 50%

In most cases it is independent of the dose, but it can change if the person’s physiological state is altered (reduced kidney or liver function)

85
Q

Give an example of a drug that does not have a fixed half life?

A

Phenytoin, an anti-convulsant, does not have a consistent half-life.

86
Q

How many lives does it usually take a drug to clear 95% from the system?

A

4-5 half lives. At this point it is considered gone, because precision instruments are requires to test at this point.

1 - 50% / 50%
2 - 25% / 75%
3 - 12.5% / 87%
4 - 6.25% / 93.75%
5 - 3.12% / 96.87%

87
Q

What changes when you mix a drug once a day vs twice a day?

A

If given once a day, the peak concentration will be higher and the trough will be lower.

However if given twice (or more) the maximum and minimum concentrations will gradually reach a more regular steady state in the blood with less variation (continuous IV perfusion is most regular)

88
Q

The time is takes to get to steady state of a drug depends on what?

A

half life alone.
Therefore, it takes 4-5 half lives to reach steady state.

89
Q

What kinds of molecules can travel through a cell membrane via passive diffusion?

A

Gases, hydrophobic molecules, and small polar uncharged molecules (such as ethanol)

90
Q

What is filtration and where does it occur?

A

When molecules diffuse through pores, observed in the kidneys.

91
Q

What are the different kinds of Protein-Assisted transport?

A

Facilitated diffusion - diffusion with a transporter
1° Active - Uses ATP
2° Active - uses gradient maintained by ATPase

92
Q

Why does chemotherapy cause nausea?

A

Because there are areas of the brain that have a leaky BBB, namely the emetic center.

93
Q

What are phase I and II chemical reaction facilitated by the liver?

A

Phase I - Drug undergoes oxidation, reduction, and or hydrolysis to add a reaction group. Most commonly, the drug is inactivated, but it can be unchanged or activated as well.

Phase II - Drug is conjugated with a highly charged, water soluble substance like glucuronic acid and (usually) inactivated

94
Q

What is glucoronidation?

A

The process of conjugating a drug with glucuronic acid in a phase II reaction

95
Q

Does drug metabolism always occurs int wo steps?

A

No, not necessarily.

96
Q

Drugs are mostly metabolized in the liver, but they can also be metabolized in the…

A

GI tract, kidneys, and lungs.

97
Q

What is the result of drug metabolism?

A

A highly charged, sometimes inactivated, mostly water soluble compound that is more readily excreted by the kidney

98
Q

What is a pro-drug? Give an example.

A

A drug that is administered in its inactive form and that is activated through metabolism.
e.g., Clopidogrel, an antiplatelet drug that is activated by hepatic and intestinal metabolism

99
Q

What is the first and most common kind of cytochrome p450 proteins?

A

CYP 3A4, followed by CYP 2D6

100
Q

Where are Cytochrome p450 enzymes found?

A

In the liver, but also in the intestinal wall. Meaning that they can decrease bioavailability before the drug even reaches the liver.

101
Q

How does cigarette smoking affect CYP activity?

A

It induces activity of CYP 1A2

102
Q

How does phenytoin affect CYP activity?

A

It induces activity of CYP 3A4

103
Q

How does rifampin affect CYP activity?

A

In induces activity of CYP 2C9

104
Q

How does ketoconazole affect CYP enzyme activity?

A

It inhibits activity of CYP 3A4

105
Q

How does erythromycin affect CYP enzyme activity?

A

It inhibits activity of CYP 3A4

106
Q

How does grapefruit juice affect CYP enzyme activity?

A

It inhibits activity of CYP 3A4

107
Q

What is the main difference between substances that induce vs inhibit CYP enzyme activity?

A

Induction is usually chronic, whereas inhibition is usually acute.

108
Q

Why are charged drugs easier for the kidneys to excrete?

A

It is possible for uncharged molecules to passively diffuse across the cell membrane and be reabsorbed.

109
Q

What role does urine pH play is drug excretion?

A

For drugs that are weak acids or bases, different pH’s could determine whether or not they are charged.

PHA 3112 (22 decks)

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