Introduction- Routes of Administration and Absorption

Question 1

What are the enteral administration methods?

Answer 1

Oral
Intrarumenal ( calcium supplements, transfaunation)
Rectal (midaz/ diazapam for seizures)

Question 2

What are the Parenteral administration methods?

Answer 2

Intravenous
Intramuscular
Subcutaneous

Question 3

What are the occasionally used parenteral administration methods?

Answer 3

• intraarterial
• intramedullary ( some contrasts, dangerous)
• intracardiac (euthasol)
• intrathecal
• intrathoracic
• subarachnoid

Question 4

What are common but less frequently used parenteral administration methods?

Answer 4

• epidural ( opioids)
• intradermal ( melenoma vaccine)
• intratracheal (atropine + epi in CPR with no ivc)
• intraperitoneal (euthasol sometimes, not common)

Question 5

Other routes mentioned?

Answer 5

• topical administration (lidocaine)
• oral transmucosal (buprenorphine)
• inhalation ( albuterol)

Question 6

What are the choices of drug administration route usually based on?

Answer 6

• Physicochemical properties of the drug
• Formulation to be used
• Therapeutic indications
the rate and extent of absorption but should • Pathophysiology of the disease
• Target species

Question 7

How can route of administration affect the patient?

Answer 7

The route of administration might influence the rate and extent of absorption but should not influence the distribution or clearance

Question 8

How do we approximate drug concentrations at tissue sites?

Answer 8

Since tissue samples cannot be collected easily, drug concentrations at the tissue site are approximated by measuring “plasma drug concentrations” (PDCs)

Question 9

What are the determinants of plasma drug concentration?

Answer 9

Drug movements (largely dependent on passive diffusion. This includes A-D-M-E)

Question 10

What is important about drug movements? Is each happen separately from one another?

Answer 10

These movements are dynamic, occurring simultaneously and their effects determine PDC at any time during the dosing interval after administration of a fixed dose

Question 11

What is absorption?

Answer 11

Absorption is the movement of the drug from the site of administration into the blood

Question 12

What routes do not require absorption?

Answer 12

All routes of administration except IV
involve an absorption process. Administrated drugs must cross one
or more membranes before getting
into the bloodstream

Question 13

What is the major obstacle of oral / gastrointestinal absorption?

Answer 13

GI-Tract present a important degree of heterogeneity relative
to morphology and physiology. This causes a regional variations in drug absorption.

Major Obstacle: The enormous interspecies diversity in comparative gastrointestinal anatomy and physiology

Question 14

In oral/ gastrointestinal absorption most drugs reach systemic circulation after absorption from?

Answer 14

Small intestine

Question 15

Rate and extent of drug absorption in the GI tract depend on?

Answer 15

o GI-pH
o Surface area
o Motility
o Concentration of drug
o permeability and thickness of the mucosal epithelium
o Intestinal blood flow.

Question 16

After GI absorption, where do drugs enter first?

Answer 16

After GI absorption, drugs enter the portal vein and then the liver. Drugs that undergo first-pass metabolism may not reach systemic circulation in concentrations
sufficiently high to cause a response

Question 17

what drugs are commonly absorbed in the sublingual area?

Answer 17

route for systemic drug (e.g. Nitroglycerin)

Question 18

what drugs are commonly absorbed in the buccal mucosa?

Answer 18

Buccal mucosa
polymer patches, feline oral sprays

Question 19

What reduces drug absorption in the esophagus and cranial stomach?

Answer 19

their cornified epithelium is a effective barrier that decreases the chance of drug absorption

Question 20

What is important about absorption in the stomach?

Answer 20

• its simple mucosa lining allows absorption
• the surface mucus may be a barrier for some drugs
• its acidity and motility creates a hostile environment for drugs and promotes the absorption father down the tract

Question 21

Where is the primary site for most drug absorption? why?

Answer 21

Small intestine
- is the primary site for most drug absorption (pH and epithelial lining)
- the blood flow to this region is much greater than to the stomach
- presence of microvilli, which increase the surface area
Epithelial and bacterial biotransformation (Presystemic metabolism)

Question 22

What species has a higher permeability to drugs than humans?

Answer 22

Dogs

Question 23

What is second 1st pass effect? Third 1st pass effect?

Answer 23

o Second first-pass effect
The epithelial cells of the intestine are endowed with the necessary enzymes for drug metabolism
o Third first-pass effect
Resident microbial population are capable of metabolizing specific drugs

Question 24

What must occur first to allow a drug to be absorbed across the intestinal mucosa?

Answer 24

In order for a drug to be absorbed across the intestinal mucosa, the drug must be first dissolved in the aqueous Intestinal mucosa

Question 25

What are the important steps to prepare a drug for absorption in the GI tract?

Answer 25

Disintegration
- A solid dosage form (e.g. tablet) physically disperses so that its particles can be exposed to the Gastrointestinal fluid (GIF)
Dissolution
- The drug molecules enter into solution, “pharmaceutical phase “

Question 26

What are important factors of parenteral administration routes?

Answer 26

Parenteral dosage forms are manufactured under strict guidelines that eliminate
microbial and particulate contamination
o Sterile preparations must be administered using aseptic techniques
o Dose must be accurate
o Painful reactions are a possibility

Question 27

What are the primary therapeutic parenteral routes? What is a benefit of these routes?

Answer 27

o The primary therapeutic parenteral routes are subcutaneous (SC) and intramuscular (IM)
o The barrier to absorption is less than found in oral or topical delivery
o The total drug dose is known and injected into well perfused tissue. Systemic capillaries drain into the venous circulation

Question 28

True or false: Parenteral routes stimulate the bodies defensive mechanisms?

Answer 28

FALSE
Parenteral routes bypass all of the body‘s defensive mechanisms

Question 29

What are the differences between SQ injections and IM injections?

Answer 29

Duration of drug action for IM is longer than IV but most often slightly shorter than SC
administration
o Usually the rate of absorption from SC administration is slightly slower than from IM sites

Question 30

Which of the 3 main parenteral routes have the slowest duration of drug action? What is the order from slowest to quickest duration?

Answer 30

SQ longest
IM 2nd
IV shortest

Question 31

What are the benefits/ reasons intraperitoneal injections are used?

Answer 31

o The peritoneal absorption is very efficient o IP injection is often used in toxicology in rodents
o Large volumes can be administered
o There is a good “ mixing” of the injection with the peritoneal fluid
o The most majority of drug absorbed after IP administration enters the portal
vein and undergoes first-pass hepatic metabolism

Question 32

In a majority of drugs, where is the drug absorbed after IP administration? What kind of metabolism does it undergo?

Answer 32

o The most majority of drug absorbed after IP administration enters the portal
vein and undergoes first-pass hepatic metabolism

Question 33

What is the benefit/ important factors of intravenous injections?

Answer 33

o No absorption process
o Immediately high blood levels
- rapid onset
o Drugs are administered directly into a vein ussually through IV catheter
o Large fluid volume can be injected
o Aqueous solutions are preferable
o Irritating and nonisotonic solutions can be injected if done slowly and carefully.

Question 34

What is the benefit/ important factors of inhalant drugs?

Answer 34

Gases, volatiles agents and fine particles usually are rapidly absorbed from the airways and alveoli into the pulmonary circulation

Question 35

Where are particles less than 2 microns inspired? 5 microns? 5-10 microns?

Answer 35

• Particles less than 2 µm (produced by nebulization) are inspired into the terminal
ducts and alveoli • Particles less than 5 µm may reach the respiratory bronchioles • Particles 5 to 10 µm in size may reach the upper respiratory tract and larger airways

Question 36

How quickly is the onset of inhalant drugs? Why?

Answer 36

Response is rapid because of the large surface area of the lungs and large blood
flow to the lungs
• Cells lining the alveoli are very thin and profusely bathed by capillaries

Question 37

Compounds absorbed in the lung will travel where? Examples

Answer 37

Compounds absorbed in the lung will enter the oxygenated pulmonary veins that drain to the systemic arterial circulation. Examples: Inhalant anesthetic ( Isoflurane)

Question 38

What are examples of topical routes?

Answer 38

Drugs can be applied topically to the skin and its adnexa
o Drugs can be applied to a variety of mucous membrane

Question 39

What are the used topical routes?

Answer 39

Sublingual
Intravaginal
Intranasal
Intrauterine
Rectal
Preputial
Ocular
Aural (otic)

Question 40

In topical administration, is achievement of effective systemic concentration important?

Answer 40

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

Question 41

What is the location of absorption in oral transmucosal or buccal drug administration? What is the major advantages of oral transmucosal or buccal drug administration?

Answer 41

o Drugs are given by mouth with the intent of absorption occurring through
the mucosa of the mouth
o The major advantage is to avoid the first-pass metabolism o Bypass the harsh GI environment

Question 42

How is the bioavailability determined of a drug?

Answer 42

The bioavailability is determined only by comparing plasma levels of a drug after a particular route of administration with the levels achieved by IV administration

Question 43

What is the bioavailability of a drug given IV?

Answer 43

1 or 100%
IV is the only route this is possible
All other routes will be less then 1

Question 44

What is the benefit of knowing bioavailability of a drug? What can it be used to predict?

Answer 44

• The greater the bioavailability or extent of absorption of a drug, the greater the anticipated pharmacologic response
• Bioavailability is used to predict drug efficacy after different routes of administration

Question 45

Which one of the following statements regarding weak
acids and weak bases is correct?
A.) Weak acids are better absorbed in alkaline conditions
B.)Weak bases are better absorbed in acidic conditions
C.) Weak acids are better absorbed in the small intestine
D.) Weak bases are better absorbed in the stomach
E.) Weak bases are better absorbed in alkaline conditions

Answer 45

E.) Weak bases are better absorbed in alkaline conditions

Question 46

Which one of the following parenteral route of
administration is not recommended for large volumes of
application?
a.) IV
b.) IP
c.) IM

Answer 46

c.) IM

Question 47

The first pass effect is most likely to occur after which one of the following route of administration?
a.) IV
b.) IM
c.) SC
d.) Oral (PO)
e.) inhaled
f.) Oral Trans mucosal (OTM)

Answer 47

d.) Oral (PO)

Question 48

What area are intrathecal injections being given into?

Answer 48

Subarachnoid space