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[Ther 201] 1st Exam Transes > Principles of Drug Disposition (Cynthia Valencia, MD) > Flashcards

Principles of Drug Disposition (Cynthia Valencia, MD) Flashcards

1
Q

Picture the Therapeutic Triangle in your head

A
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2
Q

T/F: Pharmacokinetics is concenred with the relationship between “concentration” and “dose”

A

True

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3
Q

What is the basis of pharmacogenetics?

A

One size fits all may not always apply to drugs

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4
Q

What is the connection between pharmacokinetics and pharmacodynamics?

A

Concentration

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5
Q

What are the objectives of pharmacokinetics?

A
  1. Prediction of therapeutic doses
  2. Adjustment of individual drug dosage
  3. Correlation between therapeutic blood concentration and pharmacologic effects
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6
Q

What are the uses of pharmacokinetics?

A
  1. Maximize efficacy and safety
  2. Measure drug concentration in relation with effects and toxicity
  3. Determine therapeutic human doses
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7
Q

T/F: Digitalis and cyclosporin have a high therapeutic index

A

False

They have a low therapeutic index.

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8
Q

Rats have how many times more metabolic capability than humans?

A

20 times

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9
Q

What are the factors affecting the prescribed dose?

A

Patient compliance

Medication errors

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10
Q

What are teh factors affecting administered dose?

A

Rate and extent of absorption

Body size and composition

Distribution in body fluids

Binding in plasma and tissues

Rate of elimination

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11
Q

What are the factors affecting concentration at locus of action?

A

Physiological variables

Pathological factors

Genetic factors

Interaction with other drugs

Development of tolerance

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12
Q

What are the factors affecting the intensity of effect?

A

Drug-receptor interaction

Functional state

Placebo effects

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13
Q

What variable is required to determine the quality of generic drugs?

A

Bioavailability

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14
Q

T/F: Distribution is primarily concerned with protein-binding, drug reservoirs and the apparent volume of distribution

A

True

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15
Q

What are the two metabolic enzyme systems?

A

Hepatic microsomal

Non-microsomal

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16
Q

What are the pharmacokinetic principles of elimination?

A

Clearance and half-life

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17
Q

What are the different membrane transport mechanisms?

A
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18
Q

What are the two forms of specialized transport?

A

Carrier-mediated transport and pinocytosis

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19
Q

Active transport is subject to (1), (2), and (3) by co-transported compounds.

A

(1) saturability
(2) selectivity
(3) competitive inhibition

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20
Q

Enumerate the factors that affect absorption

A

Physical state

Degree of ionization and lipid solubility

Concentration of drug

Area of absorbing surface

Gastric emptying

Route of administration

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21
Q

Define: First Pass Effect

A

Drug undergoes disintegration and dissolution even before reaching the target site

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22
Q

How many % of oral medication is destroyed by the liver before it reaches the heart?

A

90%

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23
Q

Solids must undergo what processes before absorption?

A

Disintegration

Disaggregation

Dissolution

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24
Q

On average, how long does gastric emptying take?

A

30 mins - 1 hours

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25
Q

What are the factors that affect absorption of an ingested pill?

A
  1. Disintegration time
  2. Dissolution rate
  3. Gastric emptying time
  4. Presence of drug-metabolizing enzymes in intestinal wall
  5. pH of lumen fluid
  6. Surface area
  7. Intestinal transit time
  8. Transport across columnar cell
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26
Q

T/F: All strong acids and bases are poisons.

A

True

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27
Q

T/F: Most weak acids and bases exist in their ionized form

A

False

They exist in their non-ionized forms.

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28
Q

Give examples of weak acids

A

Aspirin and acetylsalicylic acid

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29
Q

Discuss the relationship between acid/base ionization and absorption

A

Protonated weak acid and deprotonated weak base are easily absorbed

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30
Q

Give an example of a weakly basic drug

A

Amphetamine

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31
Q

How do you treat poisoning with an acidic or basic drug?

A

Alkalinize or acidify the urine to convert the compound into the more excretable form

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32
Q

Which is more hydrophobic - digoxigenin or digitoxigenin?

A

Digitoxigenin

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33
Q

Which can be orally administered - digoxigenin or digitoxigenin?

A

Digoxigenin

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34
Q

Which is more easily excreted through the kidney - digoxigenin or digitoxigenin?

A

Digoxigenin

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35
Q

GIve examples of digoxin glycosides

A

Digitoxigenin and digoxigenin

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36
Q

T/F: Higher concentration in solution = higher concentration in plasma

A

True

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37
Q

Compare the surface area of the intestines with that of the stomach.

A

It is 1000x greater.

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38
Q

Will aspirin be partially absorbed in the stomach in teh presence of HCL?

A

Yes, because it exists as the non-ionized form.

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39
Q

What is the relationship between gastric emptying time and absorption?

A

Shorter GET, greater absorption

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40
Q

Why does taking a drug before or after a meal matter?

A

Drugs can be degraded by the acidic environment of the stomach.

41
Q

What factors increase GET?

A
  1. Hot and heavy meals
  2. Vigorous exercise
  3. Lying on left side
  4. Diseases
  5. Atropine, opiate drugs and Ach
  6. Emotion, pain and stress
42
Q

What factors decrease GET?

A
  1. Fasting, hunger and cold meals
  2. Mild exercise
  3. Lying on right side
  4. Bilroth’s procedure or Dumping syndrome
  5. Prokinetic drugs like cisapride or domperidone
43
Q

What are local routes of administration in deeper tissues?

A
  1. Intraarticular
  2. Intrathecal
  3. Retrobulbar
44
Q

When is the intraarterial route of administration used?

A

Emergencies and aggressive therapy (e.g. carotid, femoral and brachial arteries)

45
Q

What are the disadvantages of the oral route of administration?

A

Patient must be conscious and not vomiting

Not suitable for unpalatable drugs

46
Q

What pain-relieving drug applied to the chest is given to cancer patients? It’s a potent opioid analgesic 1000x more potent than morphine.

A

Fentanyl TDS

47
Q

What are examples of subcutaneous modes of administration?

A
  1. Dermojet
  2. Pellet implantation
  3. Silaistic implants
48
Q

T/F: Time to steady state is independent of dosage.

A

True

49
Q

What determines the fluctuations in blood plasma drug concentration?

A

Proportional to dosage interval/half-times

50
Q

Steady state concentration is proportional to?

A

Dosage interval and CL/F

51
Q

Metabolism of estrogen and digoxin by normal gut flora result in?

A

Increase and decrease of absorption, respectively

52
Q

Why does less than 10% of isoproterenol and disodium cromoglycate reach bronchi?

A

Destruction by gut wall metabolism and first pass hepatic metabolism

53
Q

Define: Bioavailability

A

Percentage of active drug that enters systemic circulation as a parent compound

54
Q

What causes the variations in bioavailability?

A

Metabolism during absorption

55
Q

T/F: Generic drugs have to

A
56
Q

T/F: Bioequivalence is absolute bioavailability

A

False

It is relative bioavailability.

57
Q

What are the factors that affect distribution?

A
  1. Cardiac output
  2. Regional blood flow/vascular perfusion
  3. Relative permeability of tissue membranes to the drug
  4. Relative partitioning of drug between tissues and blood
58
Q

T/F: Protein-bound drug is always inactive.

A

True

59
Q

Give an example of highly bound drugs

A

Anticoagulants (99% bound; 2% free (i.e. bishydroxycoumarin))

60
Q

Protein binding less than (1) is insignificant.

A

80%

61
Q

What is the concentration of albumin in the blood plasma?

A

40 g/L

62
Q

How much drug would you need to saturate plasma albumin?

A

116 mg/L

63
Q

For drugs with a very narrow margin of safety, what is important?

A

Protein binding

64
Q

What are drugs with high Vd?

A

Quinacrine

Digoxin

Meperidine

Amphetamine

Propanolol

Procainamide

Lidocaine

Tetracycline

65
Q

What are drugs with low Vd?

A

Penicillin G

Theophylline

Gentamycin

Kanamycin

Salicylic Acid

Phenylbutazone

Tolbutamide

Warfarin

66
Q

T/F: Phase 1 of metabolism involves simple reactions, while Phase 2 involves coupling reactions

A

True

67
Q

What is the rationale behind the use of pro-drugs?

A

Active form is not palatable at times.

68
Q

Give examples of produrgs and their active forms

A

Bacampicillin/pivampicillin - ampicillin

Alpha-methyldopa - alpha-methylnorepinephrine

Enalapril - enalaprat

Fluorouracil - fluorodine monophosphate

Levodopa - dopamine

Prednisone - prednisolone

Mercaptopurine - methylmercaptopurineribonucleotide

69
Q

What is the most important drug-metabolizing reaction?

A

Oxidation

70
Q

What two drugs, when taken together, cause torsades de pointes?

A

Astemizole and clarithromycin

71
Q

What is the choice of drug for typhoid here in the Philippines?

A

Chloramphenicol

72
Q

Who are the most sensitive to adverse effects of drugs? most tolerant?

A

Japanese; Germans

73
Q

Does astemizole have the potential to cause arrythmia in the heart?

A

Yes, because it affects potassium channels in the heart

74
Q

What is the number one inducer of microsomal drug metabolizing enzyme?

A

Phenobarbital

75
Q

Where are microsomal DMEs found?

A

Liver, kidney, intestinal mucosa and lungs

76
Q

Why were infants placed under fluorescent light before?

A

Light promotes excretion of bilirubin from broken up RBCs.

77
Q

Where can non-microsomal DMEs be found?

A

Plasma, cytoplasm and mitochondria of liver cells

78
Q

Give examples of DME inhibitors

A

Allopurinol

Isoniazid

Cimetidine

Itraconazole

Clarithromycin

Ketoconazole

Ciprofloxacin

Metronidazole

Chloramphenicol

MAC inhibitors

Diltiazem

Phenylbutazone

Erythromycin

Sulfonamides

79
Q

T/F: Initial rapid decline of drug reflects distribution of drug throughout the body.

A

True

80
Q

What is the most important concept in designing a rational regimen for long-term drug administration?

A

Clearance

81
Q

T/F: Clearance is less reliable than half-life.

A

False

It’s actually more reliable because it’s more stable.

82
Q

When is clearance optimal?

A

During teenage years

83
Q

What are the formulas for clearance?

A

Cl = Vd x Ke

Cl = D/AUC

Cl = Dosing rate/Css

84
Q

What are the two types of drug-drug interaction?

A

Pharmacodynamic

Pharmacokinetic

85
Q

Describe: Pharmacodynamic Interaction

A
  1. Due to drug interaction at common receptor site
  2. Leads to effects greater than a drug acting alone
86
Q

Describe: Pharmacokinetic Interaction

A
  1. Delivery of drug is modified by another drug
  2. Increase or decrease of drug concentration at a site
87
Q

How do in-vitro drug interactions come about?

A

Pharmaceutical or chemical incompatibility

88
Q

How do in-vivo drug interactions come about?

A

Pharmacologic interaction within the body

89
Q

How do ferrous ions in oral iron supplements diminish absorption?

A

Formation of insoluble chelates of tetracyline antibodies

90
Q

What causes increased drug delivery?

A
  1. Inhibition of plasma protein binding
  2. Inhibition of hepatic drug-metabolizing enzymes (inhibition of ketoconazole)
  3. Inhibition of renal secretion (probenecid to keep penicillin around longer)
  4. Inhibition of drug transport (ketoconazole inhibits p-glycoprotein)
91
Q

What are examples of drugs that decrease absorption?

A

Antacids + metoclopramide

Cholestyramine + mineral oil

H2-receptor antagonists + sulfodecylsulfate

92
Q

What are examples of drugs that increase absorption?

A

Antacids

Metoclopramide

93
Q

What are examples of drugs that affect cellular uptake?

A

Guanidinium interacting with tricyclic antidepressants blocks hypertensive effect

94
Q

What are examples of drugs that affect protein binding?

A

Phenytoin (anticonvulsant) - Aspirin - increased free phenytoin

Warfarin - Aspirin - increased free warfarin

Phenytoin - Valproic acid - increased free phenytoin

95
Q

What are the inducers of drug oxidation?

A

Ethanol

Glutethimide

Phenobarbital

Phenytoin

Rifampin

96
Q

What are the inhibitors of drug oxidation?

A

Chloramphenicol

Cimetidine

Disulfiram

Ethanol (acute)

Isoniazid

Oral contraceptives

Propoxyphene

Valproate

97
Q

What are the drugs that affect hepatic metabolism?

A

Digitoxin + Rifampicin

Carbamazepine + Phenytoin

Acetaminophen + Oral Contraceptives (glucuronidation)

Chlordiazepoxide + Cimetidine

Theophylline + Cimetidine

Chlordiazepoxide + Oral Contraceptives (oxidation)

ALL RESULT IN INCREASED CLEARANCE

98
Q

What drugs affect renal excretion and how?

A

Decreased tubular secretion and clearance

Penicillin + Probenecid

Methotrexate + Aspirin

Procainamide + Cimetidine

Decreased tubular reabsorption & increased clearance

Quinidine + Ammonium Chloride

Increased tubular reabsorption & decreased clearance

Quinidine + Sodium Chloride

Aspirin + Ammonium Chloride

[Ther 201] 1st Exam Transes (11 decks)

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