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Introduction to Pharmacology > Routes of Administration and Absorption > Flashcards

Routes of Administration and Absorption Flashcards

1
Q

What are the main enteral routes of drug administration? Parenteral?

A

oral, intrarumenal, rectal

intravenous (IV), intramuscular (IM), subcutaneous (SQ), intraperitoneal (IP), inhalation, topical (local), oral transmucosal (OTM)

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2
Q

IV, dermal, SQ, IM, reservoir:

A
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3
Q

What 6 things determine the choice of the route of administration of a certain drug?

A
  1. physicochemical properties of the drug
  2. formulation to be used
  3. therapeutic indications
  4. pathophysiology of the disease
  5. target species
  6. manufacturer’s recommendations
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4
Q

How does the route of administration affect absorbance and clearance of the drug?

A

route of administration may influence the rate and extent of absorption, but it should not influence the distribution or clearance

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5
Q

How is the magnitude of pharmacologic response related to drug concentration at the tissue?

A

proportionately - higher concentration = higher response

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6
Q

How are drug concentrations at the tissue site approximated? Why is it approximated, rather than definitely measured?

A

measuring the plasma drug concentration (PDC)

tissue samples cannot be collected easily

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7
Q

What are the 4 major movements of drugs that affect plasma drug concentration? What do these movements largely depend on?

A
  1. Absorption from the sit of administration to systemic circulation
  2. Distribution from systemic concentration to tissues and back again
  3. Metabolism
  4. Excretion

passive diffusion

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8
Q

Describe the major steps a drug takes after it is administered.

A
  1. absorbed into circulation
  2. free drugs not bound to plasma proteins is distributed into tissue
  3. the drug will either bind to the tissues/plasma proteins or is distributed back into circulation
  4. drug is eliminated via hepatic metabolism and renal/biliary excretion of it or its metabolites
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9
Q

What is absorption? Which routes of administration need this to occur?

A

movement of drugs from the site of administration and across one or more membranes into the bloodstream

all EXCEPT IV, where the blood is delivered directly to circulation

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10
Q

What is the major obstacle related to drug GI absorption and oral route of administration across species of animals?

A

enormous interspecies diversity in comparative GI anatomy and physiology

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11
Q

What does the presence of heterogeneity in morphology and physiology of the GI tract lead to?

A

regional variants in drug absorption

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12
Q

Where are most drugs coming from when they reach systemic circulation?

A

small intestine (due to large surface area)

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13
Q

What 6 things affect the rate and extent of drug absorption in the GI tract?

A
  1. GI pH
  2. surface area
  3. motility
  4. concentration of drug
  5. permeability and thickness of mucosal epithelium
  6. intestinal blood flow
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14
Q

Where do drugs go after they are absorbed by the GI tract?

A

portal vein —> liver

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15
Q

What is first-pass metabolism?

A

phenomenon in which a drug gets metabolized at a specific location in the body that results in a reduced concentration of the active drug upon reaching its site of action or the systemic circulation (not sufficiently high enough to cause a response)

  • drugs absorbed in the intestine are metabolized in the liver as well, so it may not reach target tissue in sufficient amounts
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16
Q

What are the 2 main areas for GI absorption of drugs in the mouth?

A
  1. sublingual area - systemic drugs (nitroglycerin)
  2. buccal mucosa - polymer patches, feline oral sprays
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17
Q

Why is it difficult for drugs to be absorbed in the esophagus and cranial stomach?

A

cornified epithelium is an effective barrier that decreases chances for drug absorption

18
Q

In what way is it easy for drugs to absorb in the stomach? In what 2 ways is it difficult?

A
  1. simple mucosa
  2. surface mucus may act as a barrier
  3. acidity and motility creates a hostile environment for drugs and promotes the absorption further down the tract
19
Q

What is the primary site for most drug absorption? Why?

A

small intestine

more alkaline pH
more simple epithelial lining
higher blood flow to the small intestine compared to the stomach
microvilli increase the surface areat

20
Q

How do dogs compare to humans in regards to drug absorption?

A

dogs have a higher permeability to many drugs

21
Q

What are the second and third first-pass effects that occur in the small intestine?

A

SECOND FIRST-PASS EFFECT: the epithelial cells of the intestine are endowed with the necessary enzymes for drug metabolism

THIRD FIRST-PASS EFFECT: resident microbial population are capable of metabolizing specific drugs

(drugs are metabolized before they reach target tissue and may not cause a drug response)

22
Q

What must occur before a drug can be absorbed across the intestinal mucosa? What are the 2 major steps?

A

drug must first be dissolved in the aqueous mucosa

  1. DISINTEGRATION: solid dosage (tablet) physically disperses so that its particles can be exposed to the GI fluid
  2. DISSOLUTION: drug molecules enter into solution (pharmaceutical phase)
23
Q

What are 3 important practices used for parenteral route of administration?

A
  1. sterile preparations must be administered using aseptic techniques
  2. dose must be accurate
  3. painful reactions are a possibility
24
Q

What are the 2 primary therapeutic parenteral routes of drug administration? What is the major benefit to these routes?

A

SQ and IM

barrier to absorption is less than in oral or topical delivery - less hostile, less physical barriers (bypass the body’s defense mechanisms)

25
Q

Moderately irritating preparations can be injected IM, but what can be a possible consequence?

A

tissue reaction and necrosis

26
Q

How does the duration of drug action for IM, IV, and SQ administration compare? Rate of absorption for SQ and IM?

A

SQ > IM > IV

IM > SQ

27
Q

Why is intraperitoneal (IP) administration used? What 2 things make this route unique?

A

peritoneal absorption is very efficient and there is a good mixing of the injection with the peritoneal fluid

  1. large volumes can be administered
  2. a majority of the drug absorbed after IP administration enters the portal vein and undergoes first-pass hepatic metabolism
28
Q

What is a common use of intraperitoneal administration?

A

toxicology in rodents

29
Q

Does intravenous administration involve an absorption phase? How much of the drug can be injected?

A

NO

a large fluid volume is able to be injected

30
Q

Since IV administration is a more direct administration route, what will this result in? What types of solutions are preferred?

A

immediately high levels of the drug in the blood and rapid onset of action

aqueous
(irritating and nonisotonic solutions can be injected if done slowly and carefully)

31
Q

Which of the following parenteral routes of administration is not recommended for large volumes of application?

a. intravenous (IV)
b. intraperitoneal (IP)
c. intramuscular (IM)

A

C

32
Q

How does inhalation (pulmonary route) absorb drugs? How does the size of the partlcles affect the place of absorption?

A

gases, volatile agents, and fine particles are rapidly absorbed from the airway and alveoli into the pulmonary circulation

< 2μm (nebulization) = terminal ducts and alveoli
< 5μm = respiratory bronchioles
5-10μm = upper respiratory tract and larger airways

33
Q

Why is response so rapid during inhalation? What happens to the drug after absorption?

A

the lungs have such a large surface area and blood supply
cells lining the alveoli are very thin and profusely bathed by capillaries

oxygenated pulmonary veins —> systemic arterial circulation

34
Q

What are the main 2 ways used for topical administration? Some examples?

A
  1. applied to skin and adnexa
  2. variety of mucous membranes

sublingual, intravaginal, intranasal, intrauterine, rectal, preputial, ocular, aural (otic)

35
Q

What is unique about drug concentration and topical administration?

A

achievement of an effective systemic concentrations is often not required for what is essentially a local therapeutic effect

36
Q

What is oral transmucosal (OTM), or buccal, drug administration? What are 2 huge advantages to this route?

A

drugs are given by mouth with the intent of absorption occurring through the mucosa of the mouth

  1. avoids first-pass metabolism
  2. bypasses the harsh GI environment
37
Q

The first-pass effect is most likely to occur after which one of the following routes of administration?

a. IV
b. IM
c. SQ
d. oral (PO)
e. inhalation
d. OTM

A

D

38
Q

What is bioavailability (F)? How is it determined?

A

percentage of an administered dose of drug that reaches systemic circulation

comparing plasma levels of a drug after a particular route of administration with the levels achieved by IV administration

39
Q

Why is IV a base for calculating bioavailability (F)?

A

F for IV will always = 1 since the drug is going directly into circulation without absorption necessary, which is where drugs tend to be lost

all other routes will have an F < 1

40
Q

How is total absorption of a drug determined? What does it mean when bioavailability is high?

A

measuring the area under the concentration-time curve after drug concentrations in the blood are assayed

greater F = greater extent of absorption of a drug and anticipated pharmacologic response

41
Q

What is bioavailability used to predict?

A

DRUG EFFICACY after different routes of administration

Introduction to Pharmacology (39 decks)

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