GIT

Question 1

meclizine

Answer 1

1st gen antihistamine (H1)
minimal anticholinergic an sedating

Question 2

Vomiting centre

Answer 2

in lateral medullary reticular formation
receptors: H1, M1, NK1, 5HT3

Question 3

5HT3 antagonists

Answer 3

ondansetron, dolasetron (long QT), palonesetron (long half life)
post op nausea and post chemo (no effect on delayed nausea)

Question 4

Aprepitant

Answer 4

NK1 antagonist, central blockade CRTZ
chemo related vmiting in combo 5HT and steroid

Question 5

Steroids in post chemo

Answer 5

with 5HT3 antag to help with delayed nausea

Question 6

CRTZ

Answer 6

outside BBB 4th vent
blood and CSF
D2 receptors and opioid receptors

Question 7

Domperidone

Answer 7

D2 antagonist
Doesn’t cross BBB so EPSEs rare

Question 8

Contraindications D2 antagnists

Answer 8

e.g. metoclopromide, domperidone
phaeochromocytoma, previous EPSE, parkinsons, porphyria

Question 9

Loratadine

Answer 9

2nd gen antihistamine H1
high vD, does not cross BBB
inc QTc

Question 10

1st gen antihistamines

Answer 10

all sedating and anticholinergic ecept meclizine
diphenhydramine, promethazine

Question 11

Loperamide

Answer 11

opioid agonist doesn’t cross BBB

Question 12

Diphenoxylate

Answer 12

opioid agonist for diarrhoea
analgesic at high dose, contains atropine to stop OD

Question 13

Bulk forming laxative

Answer 13

psyllium, methylcellulose
SE bloating and flatus

Question 14

Softener laxative

Answer 14

docusate, glycerin suppository, mineral oil
mineral oil - aspiration pneumonitis and de absorption ADEK

Question 15

Stimulant laxatives

Answer 15

aloe, senna, cascara, bisacodyl
SE colonic dilation and atony
except bisacodyl cause brown pigmentation colon (melanosis coli)

Question 16

Osmotic laxatives

Answer 16

lactulos, magnesim hydroxicol,
high volume liquid stool
polyethylene glycol - pre endoscopy, isotonic and balanced with electrolytes

Question 17

Methylnaltrexone

Answer 17

opioid induced constipation

Question 18

Antacids

Answer 18

sodium bicarb - belching and metabolic alkalosis
calcium carbonate - less belching, milk alkali syndrome
Mg - osmotic diarrhoea
Aluminium - constipation
Mg +Al renally filtered - not for CRF

Question 19

H2 antagonist PK

Answer 19

A: F0.5 significent 1st pass
D: T1/2 1-4h, VD1L/KG, 70%PB
M: hepatic
E: glomerular filtration, tubular secretion

Question 20

Most and least potent H2 antagonists

Answer 20

cimetidine least 400mg BD
Famotidine most 20mg BD

Question 21

Effect of H2 antagonists

Answer 21

block 60-70% total acid
more effective inhibiting nocturnal acid secretion

Question 22

SE cimetidine

Answer 22

diarrhoea, headache fatigue
mental state change
gynecomastia and galactorrhoea
brady with rapid IV

Question 23

PPI drug type

Answer 23

prodrugs, irreversible H/K atpase inhibitors
pka 4-5 weak bases
lipophilic
inhibit 90-98% daily acid

Question 24

PPI bioavailability

Answer 24

bioavailability decreased by food
omeprazole 0.4-0.65
lansoprazole >0.8

Question 25

PK PPIs

Answer 25

A: PO/IV
D: Onset 05-2h, duration 1d, highly protein bound, small vD
M: p450 liver
E: renal

Question 26

SE PPIs

Answer 26

diarrhoea
interstitial nephritis
malabsorption B12, mg and Ca
hip #
risk C diff and other GI bugs + resp

Question 27

Sulfacrate

Answer 27

paste that binds GI ulcers 6h
SE constipation (contains aluminium)

Question 28

Bismuth compounds

Answer 28

coast GI ulcers
dark stool and tongue

Question 29

prostaglandin analogue GI

Answer 29

misoprostyl (PGE1)
dec H2 stimulated cAMP and therefore acid
inc mucous and bicarb

Question 31

Electrolyte abnormalities sodium phosphate enema

Answer 31

Hypicalcaemia and kalaemia
Hypernatraemia
Metabolic acidosis