Chapter 4 Pharmokinetics

Front 1

Define Pharmacokinetics

Back 1

The study of drug movement throughout the body

Front 2

Define absorption.

Back 2

The movement of a drug from its site of administration into the blood

Front 3

Define distribution.

Back 3

Drug movement from the blood to the interstitial space of tissues and from there into cells.

Front 4

Define metabolism. (biotransformation)

Back 4

Enzymatically mediated alteration of drug structure.

Front 5

Define excretion.

Back 5

The movement of drugs and their metabolites out of the body.

Front 6

Define elimination.

Back 6

The combination of metabolism and excretion.

Front 7

How do you maximize the beneficial effects of medications?

Back 7

You get the concentration high enough to elicit desired responses while simultaneously avoiding concentrations that are high enough to be toxic.

Front 8

When must drugs cross membranes?

Back 8

1. When entering blood from administration site.

2. When leaving the vascular sysstem to reach action site.

3. To undergo metabolism and excretion. (elimination)

Front 9

What are 3 mechanisms by which drugs cross cell membranes.

Back 9

1. Passage through a channel or pore. (Sodium and Potassium)

2. Transport systems

3. Direct penetration of the membrane.

Front 10

What is the most common way drugs cross a cell membrane and why?

Back 10

Direct penetration of the membrane is most common because most drugs are too large to pass through channels and most lack a transport system.

Front 11

What characteristic must a drug have to be able to pass through the cell membrane?

Back 11

It must be lipid soluble

Front 12

What types of drugs cannot pass through the membrane of a cell without channels or an active transport system?

Back 12

1. Polar molecules

2. Ions

Front 13

What characteristic of a drug affects absorption?

Back 13

The ionization

Front 14

Where will an acidic drug be absorbed?

Back 14

In the stomach

Front 15

What is one example of an acidic drug?

Back 15

ASA

Front 16

Where is the absorption of an acidic drug slowed and why?

Back 16

In the intestine because of the alkaline environment.

Front 17

What can we manipulate to draw toxic substances from the blood into the urine?

Back 17

Urinary pH

Front 18

What 5 factors affect drug absorption?

Back 18

1. Rate of dissolution

2. Surface Area

3. Blood flow

4. Lipid solubility

5. pH partitioning

Front 19

What must happen before a drug can be absorbed and what relationship does this have to the absorption rate?

Back 19

The drug must be dissolved. The faster the drug can be dissolved, the faster it is absorbed.

Front 20

What relationship does the drugs surface area have to the rate of absorption?

Back 20

The larger the surface area, the faster the drug is absorbed.

Front 21

How does the rate of blood flow influence absorption?

Back 21

The more blood flow, the faster the drug is absorbed.

Front 22

If a drug is highly lipid is soluble, it will dissolve more________. (quickly/slowly)

Back 22

Quickly

Front 23

What are the 3 parenteral drug administration routes?

Back 23

1. Intravenous

2. Subcutaneous

3. Intramuscular

Front 24

Define Enteral.

Back 24

Through the G.I. tract

Front 25

What are the characteristics of the I.V. route?

Back 25

1. No barriers to absorption

2. Absorption is instantaneous and complete. This is the fastest way to administer a medication.

Front 26

What does parenteral mean?

Back 26

Literally, outside the GI tract. In common parlance, it is used as by injection.

Front 27

What are the 4 advantages of the intravenous route?

Back 27

1. Rapid Onset

2. Control

3. Permits use of large fluid volumes

4. Permits use of irritant drugs

Front 28

What are the disadvantages of I.V. therapy?

Back 28

1. Irreversible

2. High Cost, difficult, and inconvenient

3. Risk for Fluid Overload

4. Risk of infection

5. Risk of embolism

Front 29

How long does it take blood to circulate throughout the body?

Back 29

1 minute

Front 30

How long will it take symptoms to appear if a drug is toxic to the central nervous system?

Back 30

15 seconds

Front 31

Why should I.V. drugs be given slowly?

Back 31

Because of the rapid effect of the I.V. route, giving drugs slowly can allow you to stop administration if dangerous side effects appear, minimizing the effects of toxic drugs.

Front 32

How much time should the nurse take to administer I.V. drugs?

Back 32

Give over at least one minute

Front 33

What are the barriers to absorption when giving a drug using the intramuscular route?

Back 33

The only barrier is the capillary wall

Front 34

What effect do enzymes have on some drugs that forces them to be given by parenteral routes?

Back 34

Some drugs can be deactivated by stomach enzymes

Front 35

What are the drawbacks of the I.M. route of medication administration?

Back 35

1. Discomfort

2. Inconvenience

3. Risk for local tissue injury and possibly nerve damage

4. Contraindicated in patients receiving anticoagulant therapy.

Front 36

What are the barriers to absorption when giving meds by the oral route?

Back 36

1. The layer of epithelial cells that line the G.I. tract

2. The capillary wall

Front 37

Why do we give a patient a higher dose of certain antibiotics on the first day?

Back 37

A large initial dose can be administered when trying to reach the plateau of the drugs effectiveness more quickly.

Front 38

What is the initial dose of a medicine called when it is larger than the doses given later?

Back 38

The loading dose

Front 39

After an initial large dose of a drug has been given, what are smaller subsequent doses called?

Back 39

Maintenance dose

Front 40

What are the 3 advantages of oral administration of a drug?

Back 40

1. Easy

2. Convenient

3. Safer than parenteral routes of administration

Front 41

Why are oral drugs safer than their parenteral counterparts?

Back 41

!. No risk of fluid overload

2. No risk of infection

3. Nor risk of embolism

4. The effects are potentially reversible

Front 42

What is one method that can be used to stop absorption of a medicine in the G.I. tract.

Back 42

Administer activated charcoal

Front 43

What does activated charcoal do?

Back 43

It soaks up drugs in the G.I. tract before they can be absorbed.

Front 44

What are the disadvantages of the oral route?

Back 44

1. Variability

2. Inactivation

3. Patient must be conscious and cooperative

4. Some oral preparations can cause local irritation

Front 45

Define Chemical equivalent.

Back 45

The same amount of drug

Front 46

Define bioavailability.

Back 46

The rate of absorption in comparison to another drug that is it's chemical equivalent.

Front 47

Why do some chemically equivalent drugs seem more or less effective than one another?

Back 47

Because the drugs can have the same composition but differing rates of disintegration and dissolution, altering the effects in the body.

Front 48

What are tablets?

Back 48

a mixture of drugs plus binders and fillers compressed together

Front 49

What are enteric-coated medicines designed for?

Back 49

They dissolve in the intestine instead of the stomach because the enteric-coating protects them from stomach acids

Front 50

Why are enteric-coated tablets used?

Back 50

1. To protect the drug from acids

2. and to protect the stomach from drugs that can cause gastric discomfort

Front 51

Describe sustained release preparations.

Back 51

Capsules filled with tiny spheres that contain the actual drug and have coatings that dissolve at different rates allowing the medicine to be released steadily throughout the day.

Front 52

What is the purpose of sustained-release capsules?

Back 52

To decrease the number of doses needed throughout the day. A beneficial secondary effect is they also produce relatively steady drug levels over an extended period of time.

Front 53

What factors influence drug distribution?

Back 53

1. Blood flow to the tissues, abscesses and tumors

2. Blood brain barrier

Front 54

What is the blood brain barrier?

Back 54

The tight capillary junctions in the central nervous system that prevent drug passage

Front 55

What 2 features can allow a drug to cross the blood brain barrier?

Back 55

1. Lipid solubility

2. a transport system

Front 56

What does P-glycoprotein do to prevent drugs from entering the central nervous system?

Back 56

Pumps them back into circulation

Front 57

Why are newborns more sensitive to drugs that act on the brain?

Back 57

Because the blood brain barrier is not fully developed at birth.

Front 58

How much of warfarin is bound to albumin?

Back 58

99%

Front 59

How much gentamycin is bound to albumin?

Back 59

10%

Front 60

What is the most important consequence of drug metabolism?

Back 60

The promotion of renal drug excretion

Front 61

Where does most drug metabolism take place?

Back 61

The liver or the P450 FAMILIES

Front 62

Where does most drug excretion take place?

Back 62

The kidneys

Front 63

What kind of drugs are the kidneys unable to excrete?

Back 63

Highly lipid soluble drugs

Front 64

Metabolic conversion can accelerate renal excretion by making lipid soluble drugs more ______________.

Back 64

Hydrophilic

Front 65

What does therapeutic action convert codeine into?

Back 65

Morphine

Front 66

What is a compound that is inactive when administered and then undergoes conversion to its active form via metabolism.

Back 66

Prodrug

Front 67

What is acetaminophen converted to that increases its danger?

Back 67

Hepatotoxic metabolite

Front 68

Define first pass effect.

Back 68

The rapid hepatic inactivation of certain drugs.

Front 69

How are drugs that undergoes rapid hepatic metabolism administered?

Back 69

Parenterally

Front 70

What happens to drugs that are bound to albumin?

Back 70

They remain in the blood

Front 71

What effect does the lipid solubility of a drug have on excretion?

Back 71

Lipid soluble drugs can be reabsorbed from the tubule back into the blood. Drugs that are not lipid soluble remain in the urine.

Front 72

What do the renal tubules contain that can pump a variety of drugs into the urine?

Back 72

P-glycoprotein

Front 73

What can we alter that can hasten excretion of a drug?

Back 73

urine pH

Front 74

What must be monitored in order to regulate drug responses?

Back 74

Plasma drug levels

Front 75

What action should the nurse take if the patient is exhibiting signs and symptoms of toxicity before administering the medication?

Back 75

Contact the provider

Front 76

What is minimal effective concentration?

Back 76

The plasma drug level below which therapeutic effects will not occur.

Front 77

Define therapeutic range.

Back 77

The range of plasma drug levels when there is enough drug present to produce therapeutic responses but not so much that toxicity results.

Front 78

Name a drug that has a narrow therapeutic range.

Back 78

Lithium

Front 79

What is the objective of drug dosing?

Back 79

To maintain plasma drug levels within the therapeutic range

Front 80

What is the objective of a loading dose?

Back 80

To get the drug to optimal levels in the blood more quickly.

Front 81

When is plateau reached?

Back 81

When a drug is repeatedly administered in the same dose, plateau will be reached in 4 half-lives

Front 82

When drugs are discontinued, how long does it take for 94% of the drug to leave the body?

Back 82

4 half-lives

Front 83

How do you achieve therapeutic range?

Back 83

The peak levels should be below toxic concentrations and the trough levels should be above minimal effective concentration.

Front 84

How do you achieve a better therapeutic range?

Back 84

1. administer by continuous infusion

2. administer by depot preparation

3. reduce the size of each dose and the dosing interval resulting in more steady peak and trough levels

Front 85

What is the relationship between the number of doses required per day and patient compliance?

Back 85

The more doses ordered in a day, the less compliant the patient is.

Front 86

Define pharmacodnamics.

Back 86

What drugs do to the body and how they do it.

Front 87

Define maximal efficacy.

Back 87

The largest effect that a drug can produce. For example, tylenol can only produce a particular level of pain relief. No matter how much of it you give, it can only produce up to that level.

Front 88

Define relative potency.

Back 88

The amount of a drug that must be given to elicit an effect

Front 89

What is a more potent drug?

Back 89

One that produces the desired effect with a lower dose

Front 90

What are receptors?

Back 90

Receptors are the chemicals in the body that most drugs interact with to produce effects.

Front 91

How many primary receptor families are there in the body?

Back 91

4

Front 92

Define agonist.

Back 92

Mimic the action of endogenous regulatory molecules

Front 93

Define antagonist.

Back 93

Blocks the action of endogenous regulatory molecules

Front 94

Define partial agonists.

Back 94

Mimic the actions of endogenous chemicals, but produce responses of intermediate intensity

Front 95

How do antagonists produce effects?

Back 95

They prevent receptors from being activated by agonists

Front 96

What are some examples of antagonists?

Back 96

1. antihistimines

2. Naloxone for opioid overdose

Front 97

Give 4 examples of drugs that do not use receptors.

Back 97

1. Antacids

2. Antiseptics

3. Saline laxatives

4. Chelating agents

Front 98

Define ED 50.

Back 98

The dose that is required to produce therapeutic effect in 50% of the population.

Front 99

What is the therapeutic index?

Back 99

A measure of a drug's safety. A large therapeutic index indicates a safer drug. A lower therapeutic index indicates a more dangerous drug.