pharmacogenetics/metabolism

Question 1

Discuss the factors which affect the bioavailability of a drug.

Answer 1

Determined by balance between pharmacodynamic response and concentration of drug at the site.
The concentration of the drug depend on the kinetics of the drug but also on the efficacy of the delivery system. (ADME).

Question 2

Discuss the strengths and weaknesses of the different routes of administration via the GI tract.

Answer 2

BUCCAL/ SUBLINGUAL:

• overcomes first-pass metabolism
• small-dissolve under tongue

RECTAL:
-localised effect
-overcomes first-pass metabolism 
VAGINAL:
-pessaries
-local effect

ORAl: TABLETS

• convenient
• accurate dose with tablets
• rapid
• reproducible
• stable
• enteric capsule to overcome breakdown by stomach acid

Question 3

Discuss the strengths and weaknesses of different preparation forms suitable for oral administration.

Answer 3

Administered via the GI tract
A. suspensions and solutions:
-good for those who cannot swallow well
-fast through nano-gastric tube or PEG tube so patient does not have to be conscious
-suspensions: particles in small volume of liquid
B. tablets/capsules
-breakdown of tablet is the rate-determine step
-enteric capsules: prevent drug from being broken down before it reaches the SI- not broken down in stomach.

Question 4

Discuss the strengths and weaknesses, with examples, of locally administered medication (topical, inhaled).

Answer 4

Topical:
-transdermal- patches allow ideal concentration to pass across skin according to difference in concentration.
bypasses the first-pass hepatic inactivation so can enter systemic circulation

Inhaled: 
pressure aerosol to lungs 
-very rapid
-direct
-small dose

Question 5

new technologies

Answer 5

Monoclonal antibodies- can target specific cancer antigens. Are used now to deliver specific cytokines.
Nanotechnologies- target precise location
Liposomes- drug is surrounded by lipid bilayer