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Pharmacology > Lecture 1: Introduction > Flashcards

Lecture 1: Introduction Flashcards

1
Q

Objectives of pharmacology?

A
  • Learn basic pharmacological principles, including pharmacokinetics and pharmacodynamics.
  • Identify advantages and disadvantages to various routes of drug administration.
  • Learn about bioavaliability, drug metabolism and excretion.
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2
Q

Pharmacodynamics?

A

What the drug does to the body

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3
Q

Pharmacokinetics?

A

What the body does to the drug.

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4
Q

Pharmacotherapeutics?

A

The study of the use of drugs.

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5
Q

Pharmacy?

A

Preparing suitable dosage forms

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6
Q

Pharmacology studies the interaction of ________ substances with _________ substances and the _________ of ______ of drugs.

A

chemical, biological, mechanisms, actions

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7
Q

What is the goal of drug therapy?

A

To prevent, cure and control various disease states.

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8
Q

Describe dose vs dosage

A

A dose refers to a specified amount of medication taken at one time.

Dosage is the prescribed administration of a specific amount, number and frequency of doses over a specific period of time.

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9
Q

Pharmacokinetics - body on drug, examines the movement of a drug over time through the body

What are the four fundamental pathways of drug movement and modification in the body?

A
  1. Absorption
  2. Distribution
  3. Metabolism
  4. Elimination
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10
Q

Absorption?

A

Drug absorption from the site of administration permits entry of the therapeutic agent (either directly or indirectly) into plasma.

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11
Q

Distribution?

A

The drug may then reversibly leave the bloostream and distribute into the interstitial and intracellular fluids.

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12
Q

Metabolism?

A

The drug may be metabolized by the liver, kidney or other tissues.

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13
Q

Elimination?

A

The drug and its metabolits are removed from the body in urine, bile or feces

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14
Q

What is the drug half life?

A

Time taken for the plasma drug concentration to reduce by 50%

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15
Q

What is the therapeutic window?

A

The plasma drug concentration above the minimum effective concentration and below the minimum toxic level.

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16
Q

What is the safety window? Would this be a relatively smaller or larger therapeutic window?

A

The bigger the therapeutic window, the larger the safety window. The smaller the therapeutic window, the higher the risk of reaching toxic levels at therapeutic concentrations.

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17
Q

What are the potential risks of shorter vs longer half lives?

A

Shorter half life: Greater withdrawal symptoms

Longer half life: Greater potential for drug to build up to dangerous levels if dosed improperly.

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18
Q

Pharmacodynamics longer definition?

A

drug on body, examines the mechanisms by which drugs produce their effects

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19
Q

What are the two general drug mechanisms of action? Which one is more common?

A
  1. Receptor-mediated
  2. Non-receptor mediated

Most drugs exert their effects through interacting with specific recepors within the body.

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20
Q

Describe the mode of actions of receptor mediated drugs?

A

The action of drugs on these receptors with either inhibit/block or else stimulate their activity.

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21
Q

What are the three ways that non-receptor mediated drugs exert their effects?

A
  1. Drugs may act through interaction with other small molecules (eg. antacids that neutralize gastric secretions)
  2. Drugs may cause non-specific changes in physical properties (eg. osmotically acting laxative drugs like MgSO4)
  3. Drugs may interact with DNA (eg. anticancer drugs that prevent DNA replication)
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22
Q

Antagonism?

A

One drug prevents the action of another drug

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23
Q

Additive?

A

The combined effects of two drugs is equal to the sumo of their individual actions.

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24
Q

Synergism?

A

The combined effects of two drugs is greater than the sum of their individual actions.

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25
Q

What is the therapeutic index? What is the formula and what do the abbreviations mean?

A

It is the measure of the safety of a drug. Therapeutic index = TD50/ED50

Toxicity Dose - TD50 is the dose that produces a particular toxicity in 50% of subjects, it is the medium toxic dose

Effective dose - ED50 is the dose of a drug that produces a pre-determined quantal (all or nothing) response in 50% of test subjects.

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26
Q

If therapeutic index, TI = 1 what does this mean about toxicity?

A

Toxicities are severe. This is rarely seen with a clinically useful drug.

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27
Q

If TI < 10 what does this mean for toxicity?

A

With a therapeutic index below 10 adverse effects are likely, so patients should be monitored for toxicities. Eg. plasma concentrations may be monitored during treatment.

28
Q

A higher TI indicates a ________ drug. OTC drugs generally have a _____ TI.

A

Safer; high

29
Q

What are the 10 routes of drug administration?

A
  1. Intravenous
  2. Intramuscular
  3. Subcutaneous
  4. Topical
  5. Transdermal
  6. Inhalation
  7. Oral
  8. Sublingual
  9. Rectal
  10. Intrathecal
30
Q

Which routes of drug administration fall under enteral?

A

Anything that reaches the GI tract: Oral, sublingual and rectal.

31
Q

Which routes fall under parenteral?

A

Drug delivery by any means other than the digestive tract. All of the others.

32
Q

What are the advantages of oral medication?

A
  • Easy to self administer
  • No risk of infection
  • Toxicity or overdose may be overcome with an antidote such as activated charcoal
  • Reversible for a while
33
Q

What are the disadvantages of oral administration?

A
  • Variable GI absorption (some cannot withstand stomach acid)
  • First pass metabolism whereby the concentration of a drug is greatly reduced before it reaches systemic circulation
  • Not possible in those who are unconscious, uncooperative or vomiting
34
Q

Grapefruit juice increases absorption of what type of drugs?

A
  • antihystamines
  • codeine
  • tranquilizers
  • cardiovascular drugs
  • AIDS drugs
35
Q

Absorption of the antibioitic erythromycin is reduced by what substances?

A
  • Pop
  • Fruit or veggie juice
  • Vitamins with iron
36
Q

What effect do dairy foods or calcium rich items have on tetracycline antibiotics?

A

Decrease absorption

37
Q

Having food in the stomach may improve the absorption of certain drugs. What is an example?

A

Antipsychotic Geodan (Ziprasidone)

38
Q

Excess dietary salt may…

A

decrease lithium levels.

39
Q

What are the advantages of sublingual administration?

A
  • Avoidance of harsh GI environment
  • Avoidance of first pass metabolism
  • Convenience of administration
  • Rapid absorption
40
Q

What are the disadvantages of sublingual administration?

A
  • Takes time to dissolve
  • May have poor taste
  • Not practical or possible for all drugs. Large molecules will not be absorbed under the tongue
41
Q

What are the advantages or rectal administration?

A
  • Bypasses approx. 50% of first-pass metabolism
  • Local or systemic action
  • Prevents destruction of drug via digestive enzymes and gastic acid
  • Useful in unconscious or vomiting patients
42
Q

What are the disadvantages of rectal administration?

A
  • Erratic, incomplete and variable rates of absorption
  • Potential for irritation of rectal mucosa
  • Uncomfortable method for many patients
43
Q

What are the main routes for parenteral administration?

A
  1. Intravenous
  2. Intramuscular
  3. Inhalation
  4. Intranasal
  5. Subcutaneous
  6. Topical
44
Q

What are the general advantages for parenteral administration?

A
  • Bioavailability is highest, avoidance of harsh GI tract
  • Control is highest over actual dosage of drug
  • Useful for unconscious patients or situations where rapid onset is important
45
Q

Advantages of intravenous administration?

A
  • Avoid first pass metabolism
  • Avoid GI breakdown (peptides, proteins)
  • Bolus or slow infusion options
  • Ok for irritating drugs
  • Large volumes are possible
  • Rapid absorption and rapid effect
46
Q

Disadvantages of IV administration?

A
  • Difficult administration
  • Irreversible, therefore more difficult to control overdose
  • Sterility is essential
47
Q

Advantages of intramuscular administration?

A
  • Can use oil-based depot preparations for slower absorption (think testosterone)
  • Fairly rapid absorption
  • Self administration possible
  • Volumes up to approx. 5mL
48
Q

Disadvantages of intramuscular administration?

A
  • Danger of inadvertent IV administration
  • Sometimes painful
49
Q

Advantages of subcutaneous administration?

A
  • Avoids GI breakdown
  • Fairly easy to self-administer
  • Systemic effects after absorption from fat
50
Q

Disadvantages of subcutaneous administration?

A
  • Absorption slower than IM (this can also be an advantage)
  • Maximum 2mL of soluble, non-irritating drugs
51
Q

Advantages of inhalation?

A
  • Can be used for gases, vapours, aerosols
  • Localized or systemic effects
  • Rapid absorption (almost as fast as IV, faster to the brain)
52
Q

Disadvantage of inhalation?

A

Many drugs cannot be inhaled.

53
Q

Describe the difference between topical and transdermal.

A

Topical is more often for local effect, though in certain cases it could be systemic, such as hormones.

Transdermal is the most common administration to provide sustained delivery of a drug.

54
Q

What are physical factors influencing absorption?

A
  • Blood flow to absorption site
  • Contact time at absorption surface
  • Total surface area available for absorption
55
Q

What are the mechanisms of cellular transportation?

A
  • Active transport
  • Endo and Exocytosis
  • Passive diffusion
  • Passive transport/Facilitated diffusion
56
Q

What is the most common method of cellular transportation for drug absorption?

A

Passive diffusion down a concentration gradient

57
Q

Compare and contrast passive diffusion and passive transport.

A

Both involve intake along a concentration gradient and neither requires energy.

Passive transport requires specific carrier proteins for passage into the interior of cells. Passive transport can be saturated, and may be inhibited as well as having high structural specificity.

Passive diffusion cannot be saturated and has low structural specificity.

58
Q

Describe active transport.

A

Active transport is energy-dependent and is driven by the hydrolysis of adenosine triphosphate (ATP). It is capable of moving drugs against a concentration gradient that is, from a region of low drug concentration to one of higher drug concentration. This type of drug delivery transports drugs of exceptionally large size across the cell membrane.

59
Q

Define bioavailability.

A

The fraction of administered drug that reaches systemic circulation.

60
Q

How is bioavaliability determined?

A

The plasma level of a drug after a particular type of administration is compared with the plasma drug level achieved by IV injection (because that is 100%).

61
Q

What are the factors that influence bioavailability?

A
  • Chemical stability
  • First pass hepatic metabolism
  • Nature of drug formulation (binders, fillers etc)
  • Solubility of the drug (hydrophilic, hydrophobic etc)
62
Q

What kind of drug is most readily absorbed?

A

One that is largely hydrophobic, but has some solubility in aqueous solutions.

(If a drug is hydrophilic it is poorly aborbed across lipid membranes. If it is extremely hydrophobic it also has a hard time because it will be insoluble in body fluid)

63
Q

What four factors does drug distribution depend on?

A
  1. Blood flow
  2. Capillary permeability
  3. Degree of binding of the drug to plasma and tissue proteins
  4. Relative hydrophobicity of the drug
64
Q

What happens when drugs bind to plasma proteins such as albumin? Is it reversible? Do different drugs bind differently?

A

The binding of drugs to albumin renders them pharmacologically inactive.

Yes it is reversible and there are differences. A drug may show high or low capacity (eg. one molecule per protein or multiple) and may have high or low affinity.

65
Q

How are drugs eliminated?

A

Drugs are most often eliminated by biotransformation and/or excretion. Excretion occurs via a number of routes, the most important being through the kidney into the urine. Other routes include the bile, intestine, lung, or milk in nursing mothers.

66
Q

Describe the two different phase reactions of metabolism (biotransformation).

A

Phase 1 reactions form products that are more reactive than the parent drug and often more water soluble.

Phase 2 reactions form products by addition of a molecule (through conjugation) to cause pharmacological deactivation and increase water solubility.

67
Q
A

Pharmacology (5 decks)

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