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Pharmacology > Ch 2 - pharmakokinetics > Flashcards

Ch 2 - pharmakokinetics Flashcards

1
Q

Pharmacokinetics def:

A

refers to what the body does to the drug

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2
Q

Pharmacodynamics def:

A

refers to what the drug does to the body

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3
Q

What are the 4 pharmacokinetic properties?

A
  1. absorption
  2. distribution
  3. metabolism
  4. elimination
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4
Q
  1. Absorption
A

directly or indirectly into the plasma

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5
Q
  1. Distribution
A

the drug may then reversibly leave the bloodstream and distribute into the interstitial and intracellular fluids

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6
Q
  1. Metabolism
A

the drug may be biotransformed by metabolism by the liver or other tissues

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7
Q
  1. Elimination:
A

The drug and its metabolites are eliminated from the body in urine, bile, or feces

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8
Q

What determines the route of administration of a drug?

A
  • the properties of the drug (for example, water or lipid solubility, ionization)
  • by the therapeutic objectives (for example, the desirability of a rapid onset, the need for long-term treatment, or restriction of delivery to a local site).
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9
Q

What are the major routes of drug administration?

A
  • enteral
  • parenteral
  • topical
  • among others (oral inhalation, nasal inhalation, intrathecal/intraventricular, tropical, transdermal, rectal)
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10
Q

What is meant by enteral administration?

A

administering a drug by mouth

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11
Q

What is the safest and most common, convenient, and economical method of drug administration?

A

enteral administration (administering a drug by mouth)

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12
Q

The different ways of enteral administration?

A
  • swallowed, allowing oral delivery
  • placed under the tongue (sublingual), or between the gums and cheek (buccal), facilitating direct absorption into the bloodstream
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13
Q

How can somebody overcome the overdose of oral drugs

A

overdose of oral drugs may be overcome with antidotes, such as activated charcoal

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14
Q

What are the difficulties involving oral administration

A
  • it is the most complicated
  • the low gastric pH inactivates some drugs.
  • a wide range of oral preparations is available including enteric-coated and extended-release preparations.
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15
Q

Enteric-coating def:

A

An enteric coating is a chemical envelope that protects the drug from stomach acid, delivering it instead to the less acidic intestine, where the coating dissolves and releases the drug.

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16
Q

Why do we use enteric-coated drugs?

A
  • useful for certain drugs (for example, omeprazole) that are acid unstable.
  • drugs that are irritating to the stomach, such as aspirin, (only dissolves in the small intestine, thereby protecting the stomach)
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17
Q

Give example of a drug that is acid unstable

A

omeprazole

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18
Q

give example of drug that is irritating to the stomach

A

aspirin

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19
Q

What does the extended-release (abbreviated ER or XR) medications do?

A

they have special coatings or ingredients that control the drug release, thereby allowing for slower absorption and a prolonged duration of action.

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20
Q

What are the advantages of ER when it comes to the half-lives?

A

ER formulations are advantageous for drugs with short half-lives
- e.g. the half-life of oral morphine is 2 to 4 hours, and it must be administered six times daily to provide continuous pain relief. Only 2 doses are needed when extended release tablets are used.

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21
Q

What are the advantages of ER when it comes to frequency of the dosage?

A
  • ER formulations can be dosed less frequently and may improve patient compliance.
  • plus, ER formulations may maintain concentrations within the therapeutic range over a longer period of time, as opposed to immediate-release dosage forms, which may result in larger peaks and troughs in plasma concentration.
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22
Q

Sublingual/buccal administration:

A

Placement under the tongue allows a drug to diffuse into the capillary network and enter the systemic circulation directly.

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23
Q

What advantages is it with sublingual administration?

A
  • ease of administration
  • rapid absorption
  • bypass of the harsh gastrointestinal (GI) environment
  • avoidance of firstpass metabolism.
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24
Q

How is the buccal administration?

A

The buccal route (between the cheek and gum) is similar to the sublingual route.

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25
Q

How is the parenteral route?

A

the parenteral route introduces drugs directly into the systemic circulation.

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26
Q

When is parenteral administration used?

A
  • drugs that are poorly absorbed from the GI tract (for example, heparin)
  • drugs that are unstable in the GI tract (for example, insulin).
  • used if a patient is unable to take oral medications (unconscious patients) and in circumstances that require a rapid onset of action.
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27
Q

E.g of drugs that are unstable in the GI tract:

A
  • insulin
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28
Q

E.g of drugs that are poorly absorbed from the GI tract

A
  • heparin
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29
Q

Bioavailability def:

A
  • bioavailability is the rate and extent to which an administered drug reaches the systemic circulation.
  • the proportion of a drug or other substance which enters the circulation when introduced into the body and so is able to have an active effect.
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30
Q

Which route of drug administration have the highest bioavailability?

A

the parenteral route

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31
Q

What are the negative side of parenteral administration?

A

these routes of administration are irreversible and may cause pain, fear, local tissue damage, and infections.

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32
Q

What does the parenteral administration provide us with?

A

Parenteral administration provides the most control over the actual dose of drug delivered to the body.

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33
Q

What are the 3 major parenteral routes?

A
  • intravascular (intravenous or intra-arterial)
  • intramuscular
  • subcutaneous
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34
Q

What are the characteristics of the parenteral administration drugs?

A

they have highest bioavailability and are not subject to first-pass metabolism or the harsh GI environment.

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35
Q

What is the most common parenteral route?

A

IV injection

36
Q

What are IV injection useful for?

A

it is useful for drugs that are not absorbed orally, such as the neuromuscular blocker rocuronium.

37
Q

What is the positive side of IV injection?

A

IV delivery permits a rapid effect and a maximum degree of control over the amount of drug delivered

38
Q

What is the difference between the drug (IV drug) being injected as a bolus compared to it being administered as an IV infusion?

A
  • injected as a bolus: the full amount of drug is delivered to the systemic circulation almost immediately.
  • administered as an IV infusion: the drug is infused over a longer period of time, resulting in lower peak plasma concentrations and an increased duration of circulating drug levels.
39
Q

Injected as a bolus (IV drug):

A

the full amount of drug is delivered to the systemic circulation almost immediately.

40
Q

Administered as an IV infusion (IV drug):

A

the drug is infused over a longer period of time, resulting in lower peak plasma concentrations and an increased duration of circulating drug levels.

41
Q

What are the advantages of IV administered drugs?

A

IV administration is advantageous for drugs that cause irritation when administered via other routes, because the substance is rapidly diluted by the blood.

42
Q

What are the negative sides of IV administering drugs

A
  • it may inadvertently introduce infections through contamination at the site of injection.
  • it may also precipitate blood constituents, induce hemolysis, or cause other adverse reactions if the medication is delivered too rapidly and high concentrations are reached too quickly.
    • -> Therefore, patients must be carefully monitored for drug reactions, and the rate of infusion must be carefully controlled.
43
Q

IM =

A

Intramuscular

44
Q

Drugs administered IM can be in……

A

aqueous solutions, which are absorbed rapidly, or in specialized depot preparations, which are absorbed slowly.

45
Q

Depot injection def:

A

an injection of a substance in a vehicle that tends to keep it at the site of injection so that absorption occurs over a prolonged period.

46
Q

What does the depot preparations consist of?

A

they often consist of a suspension of the drug in a nonaqueous vehicle such as polyethylene glycol.

  • As the vehicle diffuses out of the muscle, the drug precipitates at the site of injection.
  • The drug then dissolves slowly, providing a sustained dose over an extended period of time.
  • E.g. of sustained-release drugs are haloperidol and depot medroxyprogesterone.
47
Q

Give examples of sustained-release drugs:

A
  • haloperidol

- depot medroxyprogesterone.

48
Q

Similarities between IM injection and SC injection:

A

Like IM injection, SC injection provides absorption via simple diffusion and is slower than the IV route.

49
Q

When should the SC route not be used

A

This route should not be used with drugs that cause tissue irritation, because severe pain and necrosis may occur.

50
Q

What are the positive side of SC injections?

A
  • minimizes the risks of hemolysis or thrombosis associated with IV injection
  • may provide constant, slow, and sustained effects
51
Q

SC =

A

Subcutaneous

52
Q

Give examples of drugs commonly administered via the subcutaneous route:

A
  • insulin

- heparin

53
Q

Inhalation routes:

A
  • provide rapid delivery of a drug across the large surface area of the mucous membranes of the respiratory tract and pulmonary epithelium.
  • drug effects are almost as rapid as those with IV bolus.
54
Q

How are the drugs that are a part of the inhalation route?

A

Drugs that are gases (for example, some anesthetics) and those that can be dispersed in an aerosol are administered via inhalation.

55
Q

For who is the inhalation route effective and why?

A

It is effective and convenient for patients with respiratory disorders (such as asthma or chronic obstructive pulmonary disease), because the drug is delivered directly to the site of action, thereby minimizing systemic side effects.

56
Q

Give examples of drugs administered via inhalation:

A

it include bronchodilators, such as albuterol, and corticosteroids, such as fluticasone.

57
Q

Nasal inhalation:

A
  • Involves administration of drugs directly into the nose

- Desmopressin is administered intranasally in the treatment of diabetes insipidus.

58
Q

Give examples of drugs administered directly into the nose (nasal inhalation)

A
  • nasal decongestants, such as oxymetazoline

- corticosteroids, such as mometasone furoate

59
Q

How and when is Desmopressin used?

A

it is administered intranasally in the treatment of diabetes insipidus.

60
Q

Intrathecal/intraventricular:

A
  • The blood-brain barrier typically delays or prevents the absorption of drugs into the central nervous system (CNS).
  • When local, rapid effects are needed, it is necessary to introduce drugs directly into the cerebrospinal fluid.
61
Q

Give examples of drugs that are administered intrathecally/intraventricularly:

A

intrathecal amphotericin B is used in treating cryptococcal meningitis.

62
Q

What is intrathecal amphotericin B is used in?

A

intrathecal amphotericin B is used in treating cryptococcal meningitis.

63
Q

When is topical application used?

A

it is used when a local effect of the drug is desired

64
Q

Give example of topical application:

A

clotrimazole is a cream applied directly to the skin for the treatment of fungal infections.

65
Q

What do we achieve with the transdermal route?

A

This route of administration achieves systemic effects by application of drugs to the skin, usually via a transdermal patch.

66
Q

How effective is the transdermal route

A

The rate of absorption can vary markedly, depending on the physical characteristics of the skin at the site of application, as well as the lipid solubility of the drug.

67
Q

When is the transdermal route used?

A
  • most often used for the sustained delivery of drugs, such as the antianginal drug nitroglycerin, the antiemetic scopolamine, and nicotine transdermal patches, which are used to facilitate smoking cessation.
68
Q

Why do we use the rectal route for administration of drugs?

A

Because 50% of the drainage of the rectal region bypasses the portal circulation, the biotransformation of drugs by the liver is minimized with rectal administration.

69
Q

An antiemetic…..

A

is a drug that is effective against vomiting and nausea.

70
Q

What are the negative sides of rectal administration?

A

Rectal absorption is often erratic and incomplete, and many drugs irritate the rectal mucosa

71
Q

What is commonly used to administer antiemetic agents?

A

the rectal route

72
Q

Absorption:

A

Absorption is the transfer of a drug from the site of administration to the bloodstream

73
Q

Which route of administration does not require absorption?

A

IV

74
Q

What decides the way a drug is absorbed in the GI tract?

A

their chemical properties

75
Q

How can a drug be absorbed in the GI tract?

A
  • passive diffusion
  • facilitated diffusion
  • active transport
  • endocytosis
76
Q

Passive diffusion does not involve……

A

a carrier, is not saturable, and shows a low structural specificity.

77
Q

What is the driving force for passive absorption of a drug?

A

The driving force for passive absorption of a drug is the concentration gradient across a membrane separating two body compartments.
- drug moves from a region of high concentration to one of lower concentration.

78
Q

how are the vast majority of drugs are absorbed?

A

passive diffusion

79
Q

How does the water-soluble and lipid-soluble drugs readily move across the CM?

A
  • water-soluble drugs penetrate the cell membrane through aqueous channels or pores
  • lipid-soluble drugs readily move across most biologic membranes due to their solubility in the membrane lipid bilayers.
80
Q

Facilitated diffusion:

A
  • specialized transmembrane carrier proteins facilitate the passage of larger molecules. These carrier proteins undergo conformational changes allowing the passage of drugs or endogenous molecules into the interior of cells and moving them from an area of high concentration to an area of low concentration.
  • It does not require energy, can be saturated, and may be inhibited by compounds that compete for the carrier.
81
Q

Active transport:

A
  • involves specific carrier proteins that span the membrane
  • moves drugs against a concentration gradient -> the process is saturable.
  • Energy-dependent active transport is driven by the hydrolysis of adenosine triphosphate.
82
Q

What is endocytosis and exocytosis used for

A

it is used to transport drugs of exceptionally large size across the cell membrane.

83
Q

What is endocytosis?

A

Endocytosis involves engulfment of a drug by the cell membrane and transport into the cell by pinching off the drug- filled vesicle.

84
Q

What is exocytosis?

A
  • Exocytosis is the reverse of endocytosis.

- Many cells use exocytosis to secrete substances out of the cell through a similar process of vesicle formation.

85
Q

Give example of something that is transported by endocytosis

A

Vitamin B12 is transported across the gut wall by endocytosis

86
Q

Give example of something that is transported by exoxytosis

A

certain neurotransmitters (for example, norepinephrine) are stored in intracellular vesicles in the nerve terminal and released by exocytosis

87
Q

What are the factors influencing absorption?

A
  1. Effect of pH on drug absorption
  2. Blood flow to the absorption site
  3. Total surface area available for absorption
  4. Contact time at the absorption surface
  5. Expression of P-glycoprotein

Pharmacology (11 decks)

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