Lecture 5 Flashcards

Routes of Administration

1
Q

Key Concept

A

Active drugs must reach the drug target at sufficient concentrations and for sufficient duration to achieve desired biologic effect.

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2
Q

Steps Drug must take to be Absorbed (2)

A
  1. Absorption - movement into the bloodstream or lymphatic system
  2. Distribution - movement from blood to tissue
    Exceptions: drugs intended for only local effects or injected directly into blood

Bioavailability, distribution, and absorption are all linked

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3
Q

Absorption Key Points (4)

A
  1. Drug must move from site of administration to site of action
  2. There are membrane barrier drug must pass to reach action site
  3. Drug properties dictate movement through membranes
  4. Specialized transport properties also dictate drug movements
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4
Q

Bioavailability

A

Definition: fractional extent to which a dose of drug reaches its site of action or biological fluid (usually blood) from which drug has access to its action site

  • Function of anatomical site from which absorption takes place
  • Anatomical, physiological, and pathological factors also influence bioavailability
  • Therefore, routes of administration have a direct effect on bioavailability
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5
Q

Routes of Admin + % in Systemic Circulation

A
IV - 100%
Transdermal - 80-100%
Subcutaneous - 75-100%
IM - 75-100%
Oral, rectal, and inhalation = highly variable

Oral is highly dependent on first pass metabolism

ROUTES INFLUENCE HOW QUICKLY A DRUG REACHES ITS TARGET AND IF IT IS DISTRIBUTED BROADLY OR LOCALLY

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6
Q

First Pass Metabolism

A
  • Drugs that enter GI go through portal vein and the liver before reaching systemic circulation
  • This can significantly reduce drug’s bioavailability
  • Portal vein also takes nutrients to liver, reason why drugs must go through this first pass as well
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7
Q

Enteral

A
  • Intestine administration
  • Placement of drug directly into ANY part of GI
  • Includes oral, sublingual, and rectal
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8
Q

Parenteral

A
  • Non-intestine administration

- Includes injection (IV, IM, SQ), topical, and inhalation

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9
Q

Main factors affecting absorption & distribution are… (2)

A
  1. Amount of blood flow
  2. Rate of blood flow

SA also an important determinant of uptake

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10
Q

Parenteral Pros (3)

A
  1. Necessary for certain drugs (Ex: TNF-alphas)
  2. Bioavailability typically is more rapid, extensive, and predictable (effective dose can be delivered more accurately)
  3. May be necessary if oral isn’t an option for patient
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11
Q

Parenteral Cons (3)

A
  1. Greater infection rate, especially when done over extended periods of time
  2. May be painful
  3. May be difficult to self inject if it is needed
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12
Q

Enteral Site of Administrations

A

Differ by the following factors:

  • Saliva (mouth)
  • pH (stomach)
  • Mucus (stomach and intestine)
  • Enzymes
  • Microbes (intestine)
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13
Q

GI Absorption Factors

A

-Most occurs in the small intestine, rate depends on ionization and lipid solubility
Factors: site of GI tract (pH), GI motility, blood flow, particle size and formulation, GI enzymes, gut flora and other gut content

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14
Q

Bioavailability

A

The fractional extent to which a dose of drug reaches its site of action or a biological fluid from which the drug has access to its site of action.

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15
Q

First Pass Effect

A

Decrease of bioavailability as a consequence of hepatic metabolism and excretion

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16
Q

Absorption

A

Movement of a drug from its site of administration into the central compartment (typically bloodstream, see Figure slide 4)

17
Q

Distribution

A

Movement from the blood into the tissue and interstitial spaces.

18
Q

Enteral

A

Drug administration into any part of the GI tract

19
Q

Parenteral

A

Administration other than the GI tract

20
Q

Enteric

A

Being or possessing a coating designed to pass through the stomach unaltered and to disintegrate in the intestines