Gastro drugs

Question 1

Dosage of Ranitidine

Answer 1

150mg BD or 300mg nocte

Question 2

Dosage of Omeprazole

Answer 2

20-40mg OD

Question 3

Dosage of Loperamide

Answer 3

Acute diarrhoea: 4mg then 2mg after each loose stool for up to 5 days, usual dose 6-8mg daily

Question 4

Dosage of Mesalazine

Answer 4

1.2g-4.8g

Question 5

Fybogel dose

Answer 5

1 sachet BD after meals

Question 6

Lactulose dose

Answer 6

15ml BD in constipation
30-50ml TDS in hepatic encephalopathy

Question 7

Macrogol dose

Answer 7

1-2 sachets daily

Question 8

Senna dose

Answer 8

2-4 tablets ON

Question 9

Mechanism of Ranitidine

Answer 9

Histamine H2 receptor antagonist in gastric parietal cell. This reduces stimulation of gastric acid secretion

Question 10

Mechanism of omeprazole

Answer 10

PPI
H+K+ATPase pump at the secretory surface of gastric parietal cells
Inhibits final transport of H+ into gastric lumen, therefore inhibiting acid secretion

Question 11

Mechanism of loperamide

Answer 11

Slows intestinal motility by targeting opioid mu receptors in the myenteric plexus of the large intestine (agonist), reducing tone of circular muscle

Question 12

Mechanism of mesalazine

Answer 12

Aminosalicylate (5-aminosalicylic acid)
Inhibits COX enzymes in the colon, inhibiting mucosal production of arachidonic acid metabolites such as prostaglandins, Therefore reduces colonic inflammation

Question 13

Mechanism of bulk-forming laxatives (e.g. ispaghula husk)

Answer 13

Polysacchiaride polymers, increase stool volume activating the stretch reflex, stimulating peristalsis

Question 14

Mechanism of osmotic laxatives (e.g. lactulose, macrogol)

Answer 14

Draw water into the bowel. Accelerates transfer of gut contents through the small intestine

Question 15

Mechanism of Senna

Answer 15

Stimulant. Increases electrolyte and water secretion by the GI mucosa and increase peristalsis. Directly stimulates the myenteric plexus

Question 16

Cimetidine (H2 receptor antagonist) can cause what side effect in men?

Answer 16

Gynaecomastia and impotence

Question 17

Cimetidine should be avoided with which other medications?

Answer 17

Warfarine
Theophylline
Phenytoin
(it is a CP450 inh)

Question 18

What can PPIs and H2 receptor antagonists mask?

Answer 18

Gastric cancer symptoms - rule out red flag symptoms before starting

Question 19

What group of patients is PPIs and H2 agonists contraindicated in?

Answer 19

Pregnancy and breast feeding

Question 20

What interactions does omeprazole have?

Answer 20

Warfarin - increases anticoagulant effect
Clopidogrel - reduces antiplatelet effect

Question 21

What are some important side effects of omeprazole?

Answer 21

Rebound acid hypersecretion
Hepatitis
Interstitial nephritis
Blood disorders
C. diff
Hypomagnesaemia

Question 22

What electrolyte may you consider monitoring before and during prolonged PPI treatment?

Answer 22

Magnesium

Question 23

What is an important side effect of loperamide?

Answer 23

paralytic ileus

Question 24

What are some contraindications to loperamide?

Answer 24

Active colitis or any other condition where inhibition of peristalsis should be avoided
Should not be given to children below age 4

Question 25

What are important adverse effects of mesalazine?

Answer 25

Acute pancreatitis Blood disorders including agranulocytosis Lupus erythematosus-like syndrome (sulfasalazine) Renal dysfunction (interstitial nephritis, nephrotic syndrome

Question 26

What haematological condition must you be careful with in prescribing sulfasalazine?

Answer 26

G6PD deficiency - observe closely for signs of haemolytic anaemia

Question 27

What conditions should you have caution in prescribing aminosalicylates to?

Answer 27

Elderly Pregnancy Breastfeeding Asthma Hepatic or renal impairment

Question 28

What are the interactions for aminosalicylates?

Answer 28

Lactulose - reduces 5-ASA efficacy Azathioprine (increased risk of leucopenia) Mercaptopurine (increased risk of leucopenia) Digoxin (absorption may be reduced)

Question 29

What must you counsel patients on for aminosalicylates such as mesalazine?

Answer 29

To report any unexplained bleeding, bruising, sore throat, fever, malaise Let them know that sulfasalazine can cause yellow-orange discolouration of skin, urine and other body fluids

Question 30

Which laxative do you have to use with caution with those who are lactose intolerant?

Answer 30

Lactulose