MD3002

Question 1

What is bioavailability?

Answer 1

The fraction of unchanged drug which reaches the systemic circulation.

Question 2

What would the bioavailability of an IV drug be?

Answer 2

100% bioavailability - all drug directly to blood stream.

Question 3

What will the bioavailability of an oral drug be?

Answer 3

Will never be 100% due to barriers to absorption.

Question 4

What must be bio equivalence of generic brand be?

Answer 4

Around 80-125%.

Question 5

What percentage of drugs are now given as generics?

Answer 5

80%.

Question 6

What are some reasons against using generic drugs?

Answer 6

Clinical difference of up to 20-25%.
Subtle differences in absorption (epilepsy drugs).
Mechanical differences (eg asthma inhalers).

Question 7

What are 3 advantages of the oral route?

Answer 7

Cheap.
Safe.
Convenient.

Question 8

What are two disadvantages to using the oral route?

Answer 8

Patient compliance.

Bioavailability.

Question 9

Where is the main site of drug absorption?

Answer 9

The small intestine.

Large surface area and more neutral pH.

Question 10

Where are weak bases ionised?

Answer 10

In an acidic pH.

Question 11

Where are weak acidis unionised?

Answer 11

In an acidic pH.

Question 12

Why are weak acids still absorbed in the small intestine, where the oH is neutral and not acidic?

Answer 12

Large surface area of the small intestine compensates for the fact that most drug will be unionised in a neutral pH.

Question 13

What is the Henderson Hasselbach equation for a weak acid?

Answer 13

pKa-pH= log (AH)/(A)

Question 14

What is the Henderson Hasselbach equation for a weak base?

Answer 14

PKa-pH=log(BH)/(B).

Question 15

Why would there be a delay in drug absorption?

Answer 15

Gastric emptying.

Question 16

What will be the results of increased GI motility on drugs absorption?

Answer 16

Drug absorption will be decreased due to an increased transit time.

Question 17

What will be the effect on drug absorption when given SUBCUTANEOUSLY.

Answer 17

Slow absorption due to blood flow.

This slow release can be used as an advantage.

Question 18

What would be the effects on drug absorption when given INTRAMUSCULARLY?
Lipophilic?
Polar drugs?
High MW/very lipophobic drugs?

Answer 18

Lipophilic drugs rapidly.
Polar dugs via bulk flow.
Lipophobic drugs via lymphatics.

Highly perfumed and rapid uptake of drug.
Can still be used as a depo if in eg oil.

Question 19

Which route of admin has the highest risk of accidental overdose and why?

Answer 19

Inhalation.

Due to rate of onset

Question 20

Which route of administration is commonly used to avoid the risk of a needle stick injury.

Answer 20

Intranasal - rich, easily accessible, vascular plexus which I also avoids first pass metabolism.

Question 21

Where are the two units of control in the reflex mechanism of vomiting?

Answer 21

The Vomiting centre in the medulla.

The CTZ in the 4th ventricle.

Question 22

What is the CTZ sensitive too?

Answer 22

Chemical stimuli.

Question 23

Where is the site if action of drugs which stimulate/inhibit emesis?

Answer 23

The CTZ.

Question 24

How is motion sickness caused?

Answer 24

Caused by a discrepancy between what your eyes see and semi circular canals feel.
Origin of stimulus is therefore the semi circular canal.

Question 25

What are the four areas which feed into the vomiting centre in the medulla.

Answer 25

Higher cortical centres (emotions). CTZ. Stomach and intestine. Labyrinths (vestibular apparatus).

Question 26

Name 8 different factors which can stimulate vomiting.

Answer 26

Sensory nerve endings in the stomach or intestine. Vagal sensory endings in the pharynx. Drugs/endogenous emetic substances. Disturbances of the vestibular apparatus. Sensory stimuli from the heart and viscera. Rise in ICP. Smells, emotions and sights. Endocrine factors (oestrogen and progesterone). Migraines.

Question 27

Which drug is used to induce emesis?

Answer 27

Ipechachuana.

Question 28

How does ipechachuana work?

Answer 28

It acts locally in the stomach. | Action is important due to the presence of alkaloids.

Question 29

What alkaloids are present in ipechachuana?

Answer 29

Emetine. | Cephaline.

Question 30

What are the 5 categories of anti emetics?

Answer 30

``` H1 Receptor antagonists. Muscarinic antagonists. Phenothiazines. Metoclopramide. Cannabinoids. Steroids. 5-HT3 antagonists. ```

Question 31

What do H1 antagonists do?

Answer 31

Effective against motions sickness. Meclozine. Cyclozine. Diphenhydramine - sedative effects.

Question 32

What do muscarinic antagonists do?

Answer 32

Block Muscarinic receptor impulses from the labyrinth and visceral afferent. Widely used to prevent motion sickness. Eg hyoscine.

Question 33

What are phenothiazines?

Answer 33

``` They are neuroleptics. Eg chlorpromazine. Used for sedation in schizophrenia. Used in 1/10th dose for Emesis. Effective against CTZ triggered vomiting, not stomach induced. ```

Question 34

What is metoclopramide?

Answer 34

A dopamine antagonist which acts in the CTZ.

Question 35

What are cannabinoids?

Answer 35

Tetrahydrocannobinol (THC) and its synthetic derivative Nabollne. Effective in decreasing emesis caused by cytotoxic drugs.

Question 36

What do steroids do in emesis?

Answer 36

Effective against chemotherapy evoked emesis. | Will also help to decreased intracranial P which may be evoking emesis.

Question 37

What are examples of steroids used to help emesis?

Answer 37

Dexamethosone and methyl prednisalone.

Question 38

What do 5-HT3- antagonists do in emesis?

Answer 38

Neuroleptics which are only provided for severe emesis. | Ondansetron.

Question 39

What are the 4 classes of purgatives?

Answer 39

Bulk laxatives. Osmotic laxatives. Faecal softeners. Stimulant laxatives.

Question 40

What are some examples of bulk laxatives?

Answer 40

Bran, methyl cellulose, agar.

Question 41

How do bulk laxatives work?

Answer 41

Speed up the transitions through the gut. | Take water with it to mechanically increase peristalsis.

Question 42

How do osmotic laxatives work?

Answer 42

Chemicals retain water to = a bonus of fluid which mechanically triggers peristalsis.

Question 43

What are some examples of osmotic laxatives?

Answer 43

Magnesium sulphate, lactulose.

Question 44

How do faecal softeners work?

Answer 44

Faeces absorb water and help break up.

Question 45

What are some examples of facial softeners?

Answer 45

Liquid paraffin, sulphicuccinate.

Question 46

What do stimulant purgatives do?

Answer 46

Trigger sensory nerves to increase peristalsis.

Question 47

What are some examples of stimulant purgatives?

Answer 47

Castor oil. | Senna.

Question 48

How do muscarinic agonists/anticholinesterases work to help constipation?

Answer 48

Increase parasympathetic effect on the gut. | Used in life threatening paralysis.

Question 49

How does domperidome/motililium work?

Answer 49

Dopamine antagonist. Blocks at stomach. Tightened entry, relaxes exit and increases contractions. Decreases vomiting and feelings of sickness. Prevents regurgitation of food.

Question 50

Which two factors come together to result in diarrhoea?

Answer 50

An increase in GI motility and a decrease in absorption.

Question 51

What are the 3 approaches for treatment?

Answer 51

Maintenance of fluid balance. Anti infective agent. Anti inflammatory agent to absorb toxin.

Question 52

What are the two categories of anti motility agents?

Answer 52

Opiates/Muscarinic antagonists. | Adsorpants.

Question 53

What are some Muscarinic antagonists used in diarrhoea?

Answer 53

Codeine. Morphine. Loperamide.

Question 54

What are some adsorbents used in diarrhoea?

Answer 54

Pectin, chalk, charcoal, methyl cellulose | Bind to toxin.

Question 55

What is the most common bile pathology?

Answer 55

Gall Stones. Cholesterol choleliathiasis. Is these are calcified surgery will be needed.

Question 56

What two drugs will be used to dissolves gall stones?

Answer 56

``` Chenodeoxycholic acid (CDCA). Ursodeoxycholic acid (UDCA). ```

Question 57

Which drugs will be used to decrease the synthesis of cholesterol?

Answer 57

Statins.

Question 58

Which drugs will be used to help gall stone pain?

Answer 58

Not morphine - contraction SO oddi. Buperenone or Pethidine are better. Atropine and organic vasodilators also play a role.