Routes Of Administration

Question 1

Define pharmacokinetics

Answer 1

What the body does to the drug

• relationship between drug administration and exposure to drug (conc, time)

Question 2

Define pharmacodynamics

Answer 2

What drug does to the body

• relationship between exposure to drug (conc of drug) + response
• response: desired / adverse effect

Question 3

Exposure

Answer 3

Area under the curve (conc of drug and time)

Question 4

What are the 3 classes of routes of administration

Answer 4

1. Enteral
2. Parenteral
3. Topical

Question 5

Enteral administration

Answer 5

Administration via GI tract
Drugs becomes systemically available - gets into patients circulation and gets distributed

Question 6

Parenteral administration

Answer 6

Administered via non-GI route that allows delivery into systemic circulation

Question 7

Topical administration

Answer 7

Administrated directly to where desired therapeutic route would be
- no requirement for drug to enter the circulation

Question 8

Factors to consider when choosing the route

Answer 8

• therapeutic considerations (rapid / sustained delivery)
• effects of disease on route (medicating a vomiting patient - no oral route)
• drug properties (e.g. drug not absorbed from GI tract / drug not stable in gastric acid)
• adverse events (e.g. drug toxic of systemically bioavailable)
• patient preference

Question 9

More info on topical administration

Answer 9

• limited systemic exposure = not absorbed / or relatively small dose -> administered directly so conc low in patients when disturbuted
• anatomical sites can be used for topical and systemic administration e.g. skin

Question 10

Adv + Disadv of topical administration

Answer 10

Adv
- fast (direct)
- local
- allows high local doses to be achieved with relatively small quantities
- avoids systemic side effects

Disadv
- skills required to administer inhalers & drops
- absorption may be affected by disease
- accessibility of site

Question 11

Adv of enteral administration (oral route)

Answer 11

Adv
- convenient
- patient compliance good
- consistent absorption

Question 12

Factors that needs to be considered for enteral administration (disadv)

Answer 12

• drug must survive gastric acid (solubility may be affected)
• ^ would affect absorption from small intestines
• absorption relatively slow (fastest with empty stomach) - as with food delay in drug reaching SI
• drug must be sufficiently lipophilic (because wall of SI are lipophilic membrane) or taken up by transporter
• first pass effect - drug passes through liver before entering systemic circulation

Question 13

First pass metabolism

Answer 13

• happens when route is oral. So to prevent it administer drug via diff route
• occurs before entering systemic circulation and liver would be the site of metabolism for the drug
• ^ would mean prevents absorption of drug from SI in systemic circulation because lots of drug gets metabolised in the liver

Question 14

First pass metabolism leads to

Answer 14

• reduced bioavailability p.o.
• drug specific
• saturable
• affected by liver disease (rate of metabolism reduced = rate of first pass metabolism reduced. Can be bad because of adverse effects, reduced meta = high conc. of drug in circulation = side effects

Question 15

Enterohepatic recycling

Answer 15

• recirculating between liver and intestines
• liver produces bile which is excreted into SI via bile duct to help with absorption of cholesterol and provides a route to recycle drug.
• some drug from liver excreted into bile duct which are excreted back into SI = exposure to drug gets prolonged

Question 16

What are the ways of enteral administration

Answer 16

1. Oral
2. Sublingual
3. Buccal
4. Rectal

Question 17

Sublingual - enteral administration
Adv + disadv

Answer 17

• under tongue
• absorbed through mucosal membrane
• no first pass effect - enters systemic circulation before liver

Disadv
Some drugs aren’t absorbed by this route
Some drugs cause irritation

Question 18

Buccal - enteral administration

Answer 18

• absorbed by mucosal membrane of cheek
• no first pass effect - enters systemic circulation before liver

Question 19

Rectal - enteral administration

Answer 19

• useful in patients who are vomiting, unconscious or drug has unacceptable taste
• no first pass effect - absorbed into internal prudenal veins to inferior vena cava

Disadv
Absorption may be irregular + irrational of rectal mucosa

Question 20

Parental administration

Answer 20

Routes that leads to systemic bioavailability without going through GI tract

Question 21

Parental administration adv + disadv

Answer 21

[can control conc. of drug achieved in patient’s plasma]
Fast
slow infusion
I.m. Injection allows depot - drug slowly released into systemic circulation over a period of time

Disadv
- injection: inconvenient, requires asepsis, requires training
S.c. Only with non-irrational drug

Question 22

Drug in plasma can be

Answer 22

Bind to serum proteins (in plasma)
- binds to drugs and limits distribution into tissues
- protein- large so traps drug to serum

Question 23

ADME

Answer 23

A - absorption [needs to get into systemic circulation]
D - distribution
M - metabolism [chemical transformation of drug. Lost/gained pharmacological activity]
E - excretion [common via kidneys]

Question 24

Elimination

Answer 24

By metabolism and excretion
-> both remove pharmacology active version of drug

Question 25

Disposition

Answer 25

Everything that happens after drug absorbed - DME
- distribution and elimination

Question 26

Whole blood

Answer 26

Uncoaggulated and contains red and white blood cells

Question 27

Plasma

Answer 27

Uncoaggulated blood and red + white cells are removed

Question 28

Serum

Answer 28

Coaggulated blood and red + white cells removed

Question 29

kinetics of i.v drug administration

Answer 29

• Cmax of i.v reaches max conc. instantaneously and conc decrease as drug distributed into diff tissues + some drug gets eliminated via metabolised or excreted

Question 30

Kinetics of p.o drug administration

Answer 30

• delay corresponded due to swallowing drug then to stomach then to SI. Drug absorbed, conc in plasma increases. When conc decrease less drug = less absorption