How the body handles Drugs

Question 1

Drug Disposition

Answer 1

Intake 
Absorption
Distribution
Drug cell interaction
Metabolism
Excretion

Question 2

Oral Administration

Answer 2

+ Convenient for patient
+ Absorption from small intestine : large surface area
- Absorption can be variable
- Absorption can depend on stomach contents
- Rate of gastric emptying
- Low bioavailability

Question 3

Bioavailability

Answer 3

Amount of drug which reaches the circulation as intact drug. Proportion of drug that makes it to the blood stream

Question 4

Topical Administration

Answer 4

+ Poorly absorbed - minimises risks of overdosing
+ Patient can take at home
- Negative effect on skin
e.g Hydrocortisone cases thining of the skin.

Question 5

Transdermal Administration

Answer 5

+ Long acting
+ Useful when you want low blood levels for long periods of time.
- Variable absorption
- Drug must be very lipid soluble (has to get through cell membrane)
- Must be potent

Question 6

Rectal Administration

Answer 6

+ Local or systemic effect
+ Useful if unable to swallow
- Need training to administer
- Unreliable absorption

Question 7

Sublingual Administration

Answer 7

+ Rapid response

+ Directly to systemic circulation so avoid Liver and gut wall

Question 8

Inhalation Administration

Answer 8

+ Rapid changes in plasma concentration

+ Local or systemic effect- Difficult to ensure drug reaches site of action

Question 9

Parenteral Administration

Answer 9

Intravenous – e.g. thiopental, heparin
Intramuscular – e.g. pre-meds
Intradermal – e.g. local anaesthetics
Subcutaneous – e.g. insulin
Intrathecal (into subarachnoid space) – e.g. antivirals, chemo
Epidural (into epidural space) – e.g. during labour

+ Rapid action with lower doses
+ Bypasses stomach and liver
- Extreme care required
- Accidental overdose