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Pharmacology > Week 1 > Flashcards

Week 1 Flashcards

1
Q

Definition of Pharmacokinetics

A

Derived from two Greek words: pharmkon (drug or poison) and kinesis (motion)
The study of drug movement throughout the body

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2
Q

4 Processes of Pharmacokinetics

A
  1. Absorption
  2. Distribution
  3. Metabolism
  4. Excretion
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3
Q

Pharmacokinetics does NOT include which of the following:

Absorption
Distribution
Metabolism
Receptor activity
Excretion
A

Receptor activity

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4
Q

The major barrier to the passage of drugs is?

A

the cell membrane (double-layer of phospholipids)

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5
Q

Three Ways to Cross a Cell Membrane

A

Channels or Pores
Na+ and K+ use channels (few drugs use)

Transport Systems
Very selective - drugs with a particular structure
Carries drug from one side to the other side
Some require energy, others do not

Direct Penetration of the Membrane
Most drugs use this method

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6
Q 
Transmembrane protein which transports drugs out of cells
Liver
Kidney
Placenta
Intestine
A

Bile
Urine
Maternal Blood
Intestinal Lumen

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7
Q

Two types of Direct Penetration 
of the Membrane

A

-Lipophilic (Lipid soluble):Dissolves into lipid that composes the cell membrane and enters the cell
-Non-lipid soluble (Polar Molecules and Ions)
UNABLE to dissolve into membrane

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8
Q

Most drugs cross the cell membrane by:

  1. utilizing dedicated channels or pores.
  2. using selective transport systems.
  3. directly penetrating the cell membrane.
  4. diffusing between the cells.
A
  1. directly penetrating the cell membrane.
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9
Q

About Polar Molecules

A
  1. Uneven distribution of electrical charge
  2. No net charge
    Number of protons = number of electrons
  3. Dissolves well in water
  4. Have a net electrical charge
    -Positive or negative charge
    -Unable to cross cell membranes
    -A few utilize channels: Na, K, Ca
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10
Q

Quaternary Ammonium Compounds

A 
At least one nitrogen (N)
N has four rather than 3 bonds
--Carries a positive charge
--Unable to cross most membranes
Ex. Tubocurarine 
-Muscle relaxant
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11
Q

P-glycoprotein is a multidrug transporter found in the _________ and transfers drugs _____ the cells.

  1. cytoplasm, out of
  2. cytoplasm, into
  3. cell membrane, out of
  4. cell membrane, into
A
  1. cell membrane, out of
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12
Q

Definition of ionization

– Acid and Base

A

Process of when a base or acid become charged, the process

  • An acid gives up a proton (H+) and becomes negatively charged
  • A base accepts a proton (H+) and becomes positively charged.
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13
Q

About pH-Dependent Ionization

A
  • The pH environment plays a role in cell membrane crossing
  • Drugs exist as uncharged or charged (ionized) forms of weak bases or weak acids
  • A weak base or weak acid carries a charge based on the pH of the environment
  • –An acid will ionize in a basic (alkaline) environment
  • —A base will ionize in an acidic environment
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14
Q

Example of 
pH-Dependent Ionization

A

Aspirin is a weak acid

  • Does NOT ionize in the acidic stomach
  • –May be absorbed in the stomach
  • Does ionize in the basic intestines
  • –Ionized forms are non-lipophilic
  • –Unable to be absorbed in the intestines
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15
Q

Ion Trapping or pH Partitioning

A

If the pH gradient differs between 2 sides of a cell membrane

  • -Acidic drugs gather on the basic (alkaline) side.
  • -Basic drugs gather on the acidic side.

A drug accumulates on the side which most favors its ionization
–Ionized forms are non-lipophilic and unable to cross cell membranes

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16
Q

Acidic drugs are trapped on the ________ side of a pH gradient.

  1. acidic
  2. neutral
  3. basic (alkaline)
A
  1. Basic
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17
Q

Absorption

A
  • Movement of drug from its administration site into the blood.
  • Absorption rate determines onset of action.
  • Amount absorbed determines intensity of effects.
18
Q

Factors Affecting Absorption (first 3)

A

Rate of Dissolution
-The formulation that dissolves quickly has a faster onset of action.

Surface Area

  • The larger the surface area, the faster the absorption.
  • The small intestines have more surface area than the stomach (due to microvilli).

Blood Flow

  • The higher the blood flow, the more rapid the absorption.
  • Large diffusion gradient created.
19
Q

Factors Affecting Absorption (last 3)

A

Lipid Solubility

  • The higher the lipid solubility, the faster the absorption.
  • Highly lipophilic drugs pass through cell membranes quickly.

pH Partitioning
-Absorption increases when pH partitioning causes drug molecules to ionize in the plasma rather than administration site.

Gastric Emptying

  • Some drugs are designed to be absorbed only in the intestine
  • Delayed gastric emptying may delay absorption by minutes to hours
20
Q

Routes of Administration

A
  1. Enteral (via the GI tract)- oral or rectal
  2. Parenteral (outside the GI tract)
    - -Intravenous
    - -Subcutaneous
    - -Intramuscular
21
Q

Local vs. Systemic Effects

A

Local
-Effects seen in area of administration only

Systemic

  • Effects seen in other areas besides the site of administration
  • Drug absorbed from site of administration and distributed to other parts of the body
22
Q

Intravenous Absorption

A

No barriers to absorption with this method of delivery

Instantaneous complete absorption

Multiple advantages

  • -Hallmark – Rapid onset
  • -Control over amount of drug delivered
  • -Ability to deliver large fluid volumes
  • -Ability to give irritating drugs
23
Q

Intravenous Absorption, Disadvantages

A

Irreversible

  • –Give slowly IV push over at least 1 min
  • –Reaches brain in 15 seconds
  • –Infusing slowly allows stopping medication and preventing dangerous reactions

Fluid overload
—Monitor IV rate of infusion

Infection risk
—Avoid drug contamination

Embolism risk – blockage of vessel distant to site of administration

  • –Clots due to RBC destruction from hypertonic or hypotonic solutions
  • –Incompletely dissolved drugs

High cost, difficulty, inconveniences

24
Q

Intramuscular Absorption

A

Only barrier to absorption is the capillary wall

  • –Large spaces in between the capillary wall cells
  • –Drug passes through these spaces with ease

Rate of absorption

  • –Rapid absorption of water-soluble drugs (10-30 minutes)
  • –Increased rate of absorption if high blood flow
25
Q

Intramuscular Absorption

- Advantages and Disadvantages

A

Advantages

  • Administration of poorly soluble drugs
  • Administration of depot preparations
  • –Preparations designed to be absorbed over time
  • –Less injections

Disadvantage

  • Discomfort and inconvenience
  • Very painful injections
  • Local tissue injury
  • Nerve damage if improperly administered
26
Q

Subcutaneous Absorption

A

SC administration is almost identical to IM injection

  • -Passes readily between spaces between capillary wall cells
  • -Water-soluble drugs absorbed rapidly
  • -Increased absorption with increased blood flow

No significant barriers to absorption

27
Q

Subcutaneous Absorption

- Advantages and Disadvantages

A

Advantages

  • -Suitable for poorly-soluble drugs
  • -Depot preparations

Disadvantages

  • -Discomfort
  • -Inconvenience
  • -Potential for tissue injury
28
Q

The advantages of intramuscular absorption include:

  1. instantaneous, complete absorption.
  2. administration of poorly soluble drugs.
  3. convenience of administration.
A

Answer 2. administration of poorly soluble drugs

29
Q

Oral Absorption

A

PO abbreviation stands for per os, a Latin phrase meaning by way of the mouth

Absorbed by the stomach or intestines

30
Q

Oral Absorption- Three barriers to absorption exist for this route:

A

Epithelial cell membranes that lines the GI tract

Capillary cell membranes

P-glycoprotein

  • -In intestinal epithelial cell membranes
  • -Transports drug back into intestinal lumen
31
Q

Factors influencing oral absorption

(highly variable)

A
  • Solubility and stability of drug
  • Gastric and intestinal pH
  • Gastric emptying time
  • Food in gut
  • Coadministration of other drugs and herbals
  • Special coatings on drug preparations
32
Q

The rate of absorption may be increased by:

  1. smaller surface areas.
  2. lower blood flow.
  3. lower lipid solubility.
  4. ionization of the drug at the site of administration.
  5. formulations which dissolve quickly.
  6. delayed gastric emptying.
A

answer 5

33
Q

Drug Movement

A

All drugs taken orally must go through the liver
–Except drugs absorbed by the oral mucosa or distal segment of the rectum

Some drugs reenter GI tract

  • -Enterohepatic circulation (reabsorption from the bille)
  • -Excreted in stools
34
Q

Oral Absorption

- Advantages and Disadvantages

A

Advantages

  • -Easy, convenient, inexpensive to administer
  • -Safer than injection
  • -No risk of fluid overload, infection, or embolism
  • -Reversible by giving activated charcoal to soak up drug

Disadvantages

  • Highly variable absorption
  • Inactivation
  • –Digestive enzymes
  • –Liver enzymes with first-pass effect
  • –Inactivated by other medications, foods, herbals
  • Difficulty swallowing or unwillingness to take medication
35
Q

Oral versus Parenteral

A

Oral administration is usually preferred

Parenteral administration is necessary when:

  • Require rapid onset of action.
  • Need tightly controlled plasma levels.
  • Drugs are destroyed by gastric acid.
  • Drugs can cause severe local injury.
  • Drugs cannot cross cell membranes.
  • Need prolonged effects of drug (ex. depot preparation).
  • Unable/unwilling to take oral drugs.
36
Q

Drug Terminology

A

Chemically Equivalent
—Same amount of identical compound (drug)

Bioavailability

  • –Same drug AND
  • –Same rate and extent of absorption
37
Q

Preparations of Oral Drugs (Tablets)

A

Tablets

  • Compressed mixture
  • –Drug-Active ingredients
  • –Binders
  • –Fillers
  • –Dyes
  • Differ in bioavailability as to onset and intensity of effects
38
Q

Preparations of Oral Drugs (Enteric-coated)

A

Enteric-coated

Dissolve in intestines

  • –Absorption depends on rate of gastric emptying
  • –Some may fail to dissolve
  • –Do NOT crush!

Protection

  • —Drug from acid and pepsin
  • –Stomach from gastric discomfort

Coatings of fatty acids, waxes, shellac

39
Q

Preparations of Oral Drugs (sustained release)

A

Sustained-release

Capsules filled with variable time-release spheres

  • –Each sphere releases drug at different times
  • –Maintains steady release of drug
  • –Do NOT crush!

Permits longer times between administration

Potential for variable absorption

High cost

40
Q

Additional Routes of Administration

A

Topical
–Local treatment of skin, eyes, ears, nose, mouth, vagina

Transdermal - skin

Inhalation - lungs

Suppositories - rectal or vaginal

Injections into specific sites

41
Q

Which oral formulation may be crushed?

  1. Immediate-release tablets
  2. Sustained-release tablets
  3. Enteric-coated tablets
A

Answer 1. Immediate-release tablets

Pharmacology (25 decks)

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