controlled release drugs

Question 1

role of small intestine

Answer 1

main site of absorption and gastric uptake

Question 2

role of duodenum

Answer 2

regulates supply of material to the small intestine

Question 3

persorption

Answer 3

mode of permeation across the intestinal wall, cells are sloughed off during digestion leaving gaps so the drug can slip into circulation

Question 4

drug classification I

Answer 4

high solubility and permeability

Question 5

drug classification II

Answer 5

low solubility and high permeability

Question 6

drug classification III

Answer 6

high solubility and low permeability

Question 7

drug classification IV

Answer 7

low solubility and permeability

Question 8

high solubility

Answer 8

highest dose soluble in <250ml water over 1-7.5pH

Question 9

high permeability

Answer 9

extent of absorption in humans is >90% of administered dose

Question 10

uncontrolled delivery

Answer 10

no formulation constraint on the release of the drug from delivery system

Question 11

controlled delivery

Answer 11

a formulation constraint on the release of the drug from the delivery system

Question 12

structure of monolith devices

Answer 12

solid, all in one matrix that is hydrophobic (implants) or hydrophilic (gel layer formed on contact with water) usually made with hydroxypropyl methyl cellulose

Question 13

how do monolith devices work

Answer 13

hydroxypropyl methyl cellulose hydrates in contact with water to form a viscous gel, drug diffuses out and matrix erodes

Question 14

kinetics of monolith devices

Answer 14

zero order, square root relationship between drug release and time

Question 15

structure of membrane limiting systems

Answer 15

film coated, housed by a reservoir with a membrane limiting release, ethyl cellulose or eudragits - dose dumping!

Question 16

how do membrane limiting systems work

Answer 16

water in - drug out, immobile until water penetrates and forms a channel in which the drug can diffuse out

Question 17

structure of osmosis controlled systems

Answer 17

water insoluble core containing active drug and insoluble semi-permeable coating

Question 18

how do osmosis controlled systems work

Answer 18

osmotic pressure used to pump drug out at a constant rate, core materials undergo dissolution, suspension and solubilisation

Question 19

advantages of osmosis controlled systems

Answer 19

cheap, compatible with lots of drugs, zero order release

Question 20

disadvantages of osmosis controlled systems

Answer 20

expensive to drill, precise, integrity and consistency of coating is important

Question 21

structure of multi-particulate systems

Answer 21

multiple units typically loaded into a capsule

Question 22

how do multi-particulate systems work

Answer 22

multiple units in one capsule, same rate limiting film as membrane limiting systems

Question 23

advantages of multi-particulate systems

Answer 23

dose dumping less likely, consistent GI transit and reduced irritation

Question 24

disadvantages of multi-particulate systems

Answer 24

high cost and some technical issues

Question 25

types of gastroretentive systems

Answer 25

effervescent, bio adhesive and swelling

Question 26

structure of effervescent gastroretentive systems

Answer 26

low density systems that generate gas and float - sodium alginate/carbonate

Question 27

structure of bioadhesive gastroretentive systems

Answer 27

adhere to biological membranes to form a protective layer

Question 28

structure of swelling gastroretentive systems

Answer 28

superporous hydrogels swell rapidly to be too large to pass through the stomach - large floating system

Question 29

how do gastroretentive systems work

Answer 29

retained within the stomach for an extended period of time

Question 30

advantages of gastroretentive systems

Answer 30

useful for drugs with narrow absorption window in the intestine, good for local action

Question 31

disadvantages of gastroretentive systems

Answer 31

some controversy over safety and efficacy - bioadhesive

Question 32

why use colon targeting drugs

Answer 32

for local treatment, systemic protein absorption and chronopharmacology

Question 33

chronopharmacology

Answer 33

creates delays in the times that medications are taken

Question 34

rectal delivery

Answer 34

for more distal regions of colon, <50ml will stay in the rectum - usually pH controlled system

Question 35

colonic bacterial azoreduction delivery

Answer 35

5-aminosalicylic linked via azo bridge, cleaved by colonic bacteria so the drug can exert its therapeutic effect

Question 36

colonic bacterial polysaccharides delivery

Answer 36

using polysaccharides that are only degraded in the colon in dosage forms

Question 37

timed release systems delivery

Answer 37

insoluble capsule sealed with hydrogel plug that swells and releases drug