GI DRUGS

Question 1

mechanism of PPI

Answer 1

decrease HCl secretion and decrease pepsin

irreversibly inhibit parietal cells H/K ATPase in apical/canilicular membrane

Question 2

adverse effects of PPI

Answer 2

increased risk bony fracture in elderly
abdo pain/nausea
increased risk of C.diff
interacts with P450 potentiates warfarin 
decreases cloidogrel 
stop before endoscopy as can mask cancer

Question 3

how to they reach stomach

Answer 3

prodrug absorbed in small intestine and delivered to stomach in active form

Question 4

use of PPI

Answer 4

H.pylori eradication
prevent/treat Peptic ulcers
Dyspepsia + GORD symptom relief
Zollinger Ellison syndrome

Question 5

Antimotility drugs

Answer 5

loperamide and codeine phosphate (opioid agonists for receptors in CNS)

Question 6

what conditions are anti-motility drugs used

Answer 6

IBS

gastritis

Question 7

adverse effects of anti-motilities

Answer 7

constipation, flatulence and abdominal cramping

Question 8

contraindications of loperamide

Answer 8

no children less than 4
c.diff
acute UC (Risk of toxicmegacolon)
acute bloody diarrhoea eg. dysentry

Question 9

action of H2RAs

Answer 9

block histamine from ECL so decrease cAMP and PKA

Question 10

use of H2RAs

Answer 10

GORD symptom relief and dyspepsia

PUD (PPI preferred)

Question 11

when may H2RAs be used over PPI

Answer 11

pre op as they work faster

Question 12

side effect of cimetidine

Answer 12

gynaecomastia and potentiate warfarin

Question 13

what are alginates eg Gaviscon/peptac/mucogel (AlOH/MgOH)

Answer 13

increased pH of gastric juice and inactive pepsin

buffers (alginates increase gastric juice viscosity)

Question 14

what is Gavisocon used to treat

Answer 14

dyspepsia and GORD

Question 15

role of antimuscarinics eg. Hyoscine butyl bromide

Answer 15

blocks M3 Ach receptors: decreased muscle spasms, decreased peristalsis, decreased secretions

Question 16

when is hyoscine butyl bromide given

Answer 16

IBS

Question 17

Side effect of hyoscine butyl bromide

Answer 17

blurred vision, consitpation, dry mouth, tachycardia, urine retention

Question 18

caution antimuscarinics in?

Answer 18

cardiac arrhythmias, angle closure glaucoma

Question 19

3 types of laxative

Answer 19

stimulant, bulk, osmotic

Question 20

action of bulk laxatives eg. ispagula husk

Answer 20

hydrophilic indigestible in small intestine, attract water into stool increased bulk = increased peristalsis, improved consistency

Question 21

use of bulk laxatives

Answer 21

mild/chronic diarrhoea eg IBS, diverticular disease

constipation + faecal impaction

Question 22

when should bulk laxatives be avoided

Answer 22

intestinal obstruction and ileum (use Senna instead) do not use after surgery

Question 23

side effects of bulk laxatives

Answer 23

abdo pain and distention, ensure good hydration

Question 24

when are osmotic laxatives: citrate and phosphate enemas used

Answer 24

for rapid bowel evacuation

Question 25

action of osmotic laxative lactose

Answer 25

by osmosis water attracted to stool and increase peristalsis

Question 26

when is osmotic laxatives used

Answer 26

hepatic encephalopathy bowel surgery prep/before endoscopy consitpation + faecal impaction (use stimulant laxatives first)

Question 27

when should osmotic laxatives not be used

Answer 27

intestinal obstruction

Question 28

when should phosphate enemas be cautioned

Answer 28

HF and ascites as can cause fluid shift

Question 29

When are stimulant laxatives used eg. Senna, biscocdyl, glycerol suppository

Answer 29

constipation use suppository for faecal impaction avoid in intestinal obstruction can perforate avoid rectal preps in anal fissures and haemorrhoids offered to people taking opioid analgesia

Question 30

side effects of Senna

Answer 30

``` reverse melanosis coli irreversible atonic colon diarrhoea cramping abdo pain ```

Question 31

Aminosalcylates (5-ASA) eg. mesalazine action

Answer 31

anti-inflammatory and immune suppression | active in disral colon

Question 32

when is mesalazine used

Answer 32

1st line UC

Question 33

side effect of mesalazine

Answer 33

GI upset + headache

Question 34

what is enema mesalazine> suppository advantage

Answer 34

extends to sigmoid colon

Question 35

when is suppository > mesalazine advantage

Answer 35

better musosal headache

Question 36

when is D2 Dopamine receptor antagonise eg. metoclopramide/doperidone used

Answer 36

GORD if not PPI response Vomitting due to emergency hormone contraception N+V

Question 37

when is doperidone used

Answer 37

drug/chemo induced N+V (CINV)

Question 38

what does D2D receptor antagonists act on

Answer 38

CTZ (chemoreceptor trigger zone) | detects emetrogic substances in blood eg. chemo

Question 39

action of doperidone

Answer 39

antagonist activity 5HT3 agonist activity at 5HT4 doesn't cross BBB

Question 40

side effects of D2 receptor antagonists

Answer 40

metrclopramide: avoid in children, extrapyramidal effects: spastic tortacolis, motor restlessness, uculogynic crises

Question 41

H1 RA eg. cyclizine action

Answer 41

competitive inhibitor of H1 receptors in VC can cause sedation block M1 Ach vestibular apparatus

Question 42

when is cyclizine used

Answer 42

motion sickness vertigo post op sickness PONV

Question 43

2 anti motion sickness drugs

Answer 43

cyclizine, hyoscine hydrobromide

Question 44

when should cyclizine be avoided

Answer 44

risk of hepatic encephalopathy and prostatic hyperplasia | avoid in driving, heavy machinery as can cause sedation

Question 45

adverse effects of cyclizine

Answer 45

sedation transient tachycardia dry mouth drowziness

Question 46

action of phenothiazines eg. procloperazine

Answer 46

competitive antagonist of D2, H1 and M1 in VC, vestibular system and peripherally in gut

Question 47

use of procloperazine

Answer 47

vertigo N+V chemo induced (use doperidone first) psychiatric disorders

Question 48

avoid procloperazine in

Answer 48

liver disease and prosthetic hyperplasia

Question 49

adverse effects of procloperazine

Answer 49

drowsiness, postural hypotension, D2 block, parkonism, long QT

Question 50

action of 5HT3 eg. ondansetran

Answer 50

competitive antagonist of 5HT3 (inotropic) receptors act on CTZ, NTS and visceral afferens 5HT released from enterochaffin cells in gut stimulate vagal afferent that via NTS activate CTZ

Question 51

use of 5HT3 receptor antagonists

Answer 51

chemo and radon N+V post op N+V IBS

Question 52

adverse effects of 5HT3 receptor antagonists

Answer 52

long QT constipation diarrhoea bleeding

Question 53

contraindications of 5HT3 RA

Answer 53

``` stricture toxic megacolon ischaemic colitis intestinal obstruction crohns diverticulits UC intestinal obstruction sever prolonged consipation ```