Administration . Absorption and Distribution of Drugs

Question 1

Pharmacokinetics is …

Answer 1

How the body affects a specific drug after administration

Question 2

Draw and lablel the pharmacokinetic curve

Briefly explain what is happening at each interval

Answer 2

Refer to Notes

Question 3

The administration of drugs can be classified into different groups . What are they?

Answer 3

Enteral

Parenteral

Question 4

A drug that is administered via the enteral route involves ..

Answer 4

Mouth
oesophagus 
stomach 
small and large intestines 
constituents of the GI tract

Question 5

A drug that is administered via the parenteral route involves ..

Answer 5

may cross epithelium if applied topically to skin

or may avoid epithelium through inhalation and absorbed by lungs or forms of injections

Question 6

State the enteral routes of administration

Answer 6

sublingual
oral
buccal
rectal

Question 7

state the parenteral routes of administration

Answer 7

injections
inhalations
cutaneous

Question 8

What is an intrathecal injection

Answer 8

an injection into the spinal canal or into subarachnoid space so it reaches the cerebrospinal fluid

Question 9

what is an intraperitoneal injection

Answer 9

an injection made into the body cavity - LBP pts

Question 10

discuss what you know about the sublingual route of administration

Answer 10

sublingual means under the tongue
involves placing pill or spray under the tongue and floor of oral cavity
connective tissue in this area is highly perfused which means drug only has to interact with these enzymes - liver is bypassed
rapid means of absorption
ideal for emergency conditions like use of GTN for rapid relief of sx of angina

Question 11

Discuss what you know about the buccal route of administration

Answer 11

buccal means between pts cheeck and gum - not swallowed
liver bypassed
presence of saliva help breakdown of drug
taste may not be nice

Question 12

What is meant by the first pass effect ?

Answer 12

a concept where conc of drug avail to reach the systemic circulation is reduced due to processes it undergoes like metabolism

Question 13

Cirrhosis is

Answer 13

Cirrhosis is the severe scarring of the liver and poor liver function The scarring is most often caused by long-term exposure to toxins such as alcohol or viral infections.

Question 14

Draw and label a diagram of the hepatic portal system

Answer 14

Refer to notes

Question 15

What does the hepatic portal system do

Answer 15

carries blood from parts of the GI tract to the liver

Question 16

Give examples of oral drug forms

Answer 16

Capsules - less compressed together , shell of capsule dissolves then contents free
tablets - compressed - disintegrates into smaller
pills
enteric coatings - barrier applied to tablet to protect t from the acidity of the stomach , in other conditions able to break down
elixirs - active ingredient mixed with liquid
suspensions - liquid with small pieces of drug. drug is not completely dissolved in drug

Question 17

Briefly discuss what you know about the rectal form of drug administration

Answer 17

end of GI tract using suppository
absorbed by the rectums blood vessels
useful for vomiting patients unable to keep anything down
surface area avail for absorption is reduced - no microvilli
allows some bypassing of the first pass effect because venous drainage in this area done by inferior and middle rectal vein with minimal help from hepatic porta system

Question 18

state the factors which influence absorption of drugs in the GI tract

Answer 18

• Surface Area
• PH of gastro intestinal contents
• Active transport
• Plasma protein binding
• Gastric emptying
• blood flow
• formulation

Question 19

PH of gastro intestinal contents

Answer 19

the PH conditions will affect the ionisation of molecules
ionisation is process by which molecules that lose electron gain positive charge and molecules that gain electron gain a negative charge.
- mucosa lining of GI tract - impermeable to ionised molecules
- acidic drugs –> acidic conditions of stomach stay in un ionised formed and absorbed in stomach

Question 20

Surface Area

Answer 20

small intestine - high conc of microvilli so has larger surface area 1000x more than of stomach - absorption more efficient in areas of great SA

Question 21

Gastric emptying

Answer 21

Related to how fast drug/food leaves the stomach . If drug moves quickly absorption will be reduced

Question 22

Blood flow

Answer 22

intestine - good blood flow- maintains conc gradient . Drug moves from high to low conc
BF to intestine is greater than stomach - absorption favoured here

Question 23

Plasma Protein Binding

Answer 23

drug molecules may bind to plasma protein and if occurs it will become inactive .
only free drug molecules can be pharmacologically active

Question 24

Formulation

Answer 24

small particle size - faster rate of absorption

large particle size - delayers absorption

Question 25

Active Transport

Answer 25

Transportation of molecules across membranes ( passive or active )

Question 26

What is an intravenous injection

Answer 26

substance that is given directly into vein all of it enters systemic circulation useful for quick rapid response

Question 27

Disadvantages of intravenous injection

Answer 27

requires trained personnel sometimes difficult to find vein expensive ( sterility / cost of preparation and transport/storage)

Question 28

what is a subcutaneous injection

Answer 28

substance administered into the subcutis layer often used to deliver vac and meds ( insulin) layer has few BV - slows absorption - massage to help to maintains effect locally - vasoconstriction ( painful / finding site for repeated injection can be issue)

Question 29

what is an intramuscular injection

Answer 29

substance given directly into muscle lots of BV - faster absorption used to deliver large volume of meds - antipsychotic drugs - lasting effects - requires trained personnel

Question 30

sites for intramuscular injection depend on what?

Answer 30

pts age type of drug volume

Question 31

state the different sites for intramuscular injections

Answer 31

deltoid muscle of arm - small volume vastus lateralis - newborns and infants ventrogluteal - pts lying on side ( most comf and safe for adults ) dorsogluteal (less likely to be used due to proximity to sciatic nerve) last resort in adults.

Question 32

Explain the inhalation route of administration of a drug

Answer 32

pt inhales - lung , has a large SA and BF rapid absorption bypasses liver and first pass effect absorption of gasses relatively efficient - Larger particle size = less absorption and more local action, small particle size = favours systemic absorption

Question 33

What is absorption ?

Answer 33

transfer of drug from site of administration into the blood stream

Question 34

in order for a drug to get into the bloodstream what does it have to cross

Answer 34

several semi permeable membranes

Question 35

what is a cell membrane made up of

Answer 35

phospholipid bilayer - hydrophillic heads - phosphate - hydrophobic tails - two fatty acid chains - layer is 10nm thick

Question 36

how do small molecules cross cell membranes

Answer 36

- forces that hold the CM - weak - drugs may be able to slip through lipids in bilayer . Can only happen if drug is small , lipid soluble and lipophilic - some drugs may need help so travel through aqueous pores - specific molecules may recognise certain drugs and help them cross using carrier molecules passively ( s energy) or actively - pinoocytosis

Question 37

what do you know about diffusion

Answer 37

``` passive process requires conc gradient particle size - small membrane - permeable ability of drug to pass through membrane depends on lipid solubility ```

Question 38

what is lipid solubility

Answer 38

ability of drug to dissolve in lipid

Question 39

what is facilitated diffusion

Answer 39

drug molecules combine with carrier proteins to transport through membrane specific - only recognised molecules flows with conc gradient

Question 40

what is active transport

Answer 40

requires energy ATP | goes against conc gradient

Question 41

what is pinocytosis

Answer 41

form of endocytosis molecules bought into cell when part of cell membrane encloses around them and makes then move from outside to inside of cell molecules may be released into cell or remain in vesicle

Question 42

What is distribution?

Answer 42

once drug has reaches bloodstream it circulates around the body - and will move into tissues of the body and site of action

Question 43

quantify distribution

Answer 43

apparent volume of distribution linked to conc present in plasma

Question 44

water of body can be distributed into four parts in the body . what are they and how much does each represent

Answer 44

Refer to notes

Question 45

Briefly explain the effect of solubility on a drug

Answer 45

if a drug is lipid soluble it will be able to pass through the cell membrane easily and reach all fluid compartments and have widespread distribution if a drug is water soluble it will be difficult to cross the cell membrane , it will stay in the plasma and interstitial fluid and continue circulating leaving itself open to be metabolised by the liver and eliminated without reaching tissue

Question 46

Give an example of plasma protein and give an example of a drug which binds to a protein

Answer 46

Albumin - warfarin 97% binds to protein leaving only 3% to be active , metabolised and excreted

Question 47

what drugs will bind to the protein albumin

Answer 47

- bind likely to acidic drugs if that becomes saturated - lipoprotein - basic drugs - alpha 1 acid glycoprotein

Question 48

what is volume of distribution

Answer 48

theoretical volume required to contain the total amount of administered drug at the same conc as the plasma Vd = total amount of drug in body/ drug blood plasma conc

Question 49

importance of blood flow

Answer 49

heart liver kidney and brain - seconds to mins muscles , skin , fat mins - hours bones - days - weeks