Factors affecting GIT

Question 1

what is the major site of absorption,

Answer 1

regardless of the dominant ionization state the small intestine is the major site of absorption

Question 2

describe the different states in terms of absorption

Answer 2

if tablets api has to be released from the formulation in order that it can be absorbed

if suspension, api is in solid form but at least already dispersed and so can dissolve more quickly

solution, API already dissolved so faster transit and absorption

Question 3

what can occur as long as some API absorbed

Answer 3

distribution
action at site of action
side FX elsewhere
metabolism by liver
excretion of API and its metabolites

Question 4

what are granules

Answer 4

tablets are mostly by compressing api in the form of granules made with excipients, when the tablet breaks down it breaks into these granules.

Question 5

what do granules break down into

Answer 5

particles

Question 6

what do API particles dissolve into

Answer 6

api molecules i

Question 7

what physicochemical factors affect dissolution

Answer 7

particle size, smaller particle = larger surface area so faster dissolution

dissolution rate depends upon the api solubility because the more soluble faster the dissolution

Mixing and stirring can reduce conc gradient encouraging more to dissolve

Question 8

what affects sollubility

Answer 8

salt form have higher solubilities

crystal form of API (polymorph)

hydration state of API

Question 9

what passes through the GIT wall

Answer 9

unionised

Question 10

what is an enteric coating

Answer 10

a special acid insoluble polymer coating designed to protect the APi from the acidic environment of the stomach

polymer only dissolves in the higher pH environment of the small intestine

therefore dosage form stays intact until is has passed through the stomach

Question 11

what is the site of action for aminosalicylates

Answer 11

large intestine and it is used for inflammatory bowel disease

Question 12

what effect the time it takes for a drug to leave the body

Answer 12

when fed the formulation empties along wit hte food more slowly than it would on an empty stomach so on a large meal it increases the rate of gastric emptying, relative to a small meal.

Question 13

what interacts with milk

Answer 13

tetracycline + calcium ions

Question 14

what interacts with grapefruit juice

Answer 14

statins as there is an increased risk of side fx

Question 15

why do we avoid grapefruit juice when taking statins

Answer 15

compounds in the juice inhibit GIT enzymes that normally break down some % of the statins in the GIT

thus bioavailability increased leading to potential overdosing

Question 16

what does transit time change with

Answer 16

Age (elderly)
Varies with disease state, diet and GIT flora
Varies with medication

Question 17

what effect does first pass metabolism on cP

Answer 17

leads to significant variations in Cp between patients depending upon liver enzyme activity

Question 18

what alternative routes exist

Answer 18

parenteral

• sublingual
• inhalation
• transdermal
• injection

Question 19

when does something go through first pass metabolism

Answer 19

Anything absorbed from the GIT undergoes through first pass metabolism

Question 20

once a drug is in the blood what can happen

Answer 20

act at the target site (what we want)

act at other sites i.e. side effects

reversibly bind to proteins in the blood

be metabolised

be excreted

Question 21

what can happen with adsorption

Answer 21

drug can adsorb ont oa foot and not be released for absorption by the body

Question 22

what is efflux

Answer 22

some compounds once absorbed are actually pushed back out into the GIT lumen to avoid toxicity

Question 23

how is efflux achieved

Answer 23

p- glycoproteins which handles xenobiotics and therefore handles a lot of APIs

Question 24

what does buccal mean

Answer 24

cheek

Question 25

what does sub lingual mean

Answer 25

under the toungue