Prescribing - Gastroenterology Flashcards
What is Rantidine’s drug class?
H2 receptor antagonist
How does Ranitidine work?
reduces stimulation of gastric acid secretion
What are common side effects of Ranitidine?
Diarrhoea
Headache
Dizziness
When is Ranitidine contraindicated?
Hepatic or renal impairment requires dose reduction
Avoided in Pregnancy
In patients with red flags for gastric cancer- only prescribe if ruled out.
What is Cimetidine ?
H2 receptor antagonist
What is an important side affect of Cimetidine?
Gynaecomastia
What is an absolute contraindication of Cimetidine?
If on Warfrin, theophylline or phenytoin as cimetidine is a Cytochrome P450 inhibitor
What is Omeprazole?
A PPI
How does Omeprazole work?
inhibits final transport of hydrogen ions into the gastric lumen meaning less acid is secreted
What is the follow up for Omeprazole?
Prescribe at lowest effective dose for shortest period of time possible. If needed long term periodic reviews need to be had (every 8 weeks or so)
Magnesium levels need to be monitored
What are cautions of PPIs?
PPIs may mask symptoms of gastric cancer – in patients presenting with ‘alarm features’ (bleeding, dysphagia, recurrent vomiting, weight loss) it is important to rule out malignancy before commencing PPI therapy.
What drug interactions occur with Omeprazole?
Warfarin - increase anticoagulant effect)
Clopidogrel - may reduce antiplatelet effect)
What drug class is Loperamide?
Antimotility
How does loperamide work?
Is an agonist to the opioid mu receptors in the myenteric plexus of the large intestine. This reduces the tone in the large intestine muscles inhibiting peristalsis slowing motility
What are side effects of Loperamide
Abdominal cramps Dizziness Flatulence Headaches Nausea
Paralytic ileus!!!
What are contraindications to Loperamide?
Avoid in any kind of Colitis or if there is suspicion of infective diarrhoea
What is important to communicate to patients about loperamide?
Not to be given to children under 4
Maintain adequate fluids
Mesalazine (5 ASA) drug class?
Aminosalicylates
Olsalazine, Sulfasalazine, Balsalazide
how does Mesalazine work?
Inhibit mucosal production of arachidonic acid metabolites such as prostaglandins. Reducing colonic inflammation
What is Masalazine used
Crohns and Ulcerative colitis
What are side affects of Mesalazine?
GI upset (diarrhoea, nausea, vomiting, abdominal pain)
Acute pancreatitis!!
Agranulocytosis!!
Renal dysfunction!! (interstitial nephritis, nephrotic syndrome)
What is an important side effect of Sulfasalazine?
Lupus erythematosus-like syndrome
When is Mesalazine Contraindicated?
Complete contradiction in Renal impairment
elderly, pregnancy and breastfeeding, patients with a history of asthma
What are interactions of Aminosalycates?
Lactulose (reduces efficiency of 5 ASA)
Azathioprine (increased risk of leucopenia)
Mercaptopurine (increased risk of leucopenia)
Digoxin (absorption of digoxin may be reduced,)
What is the follow up for Aminosalycates?
FBC, LFTs, ESR, CRP, U+E should be checked monthly for the first 3 months then 3 monthly thereafter (U+E annually unless theres some renal impairment)
How would you check that blood dyscrasia wasn’t occurring?
apart from checking bloods asking about oral ulceration/sore throat, unexplained rash or unusual bruising at every consultation.
What is important to communicate to patients about aminosalycates?
Report any unexplained bleeding, bruising, purpura, sore throat, fever or malaise that occurs during treatment.
Sulfasalazine may cause yellow-orange discoloration of skin, urine and other body fluids.
What are the three types of laxatives
Bulk forming
Osmotic
Stimulant
What is an example of bulk forming laxatives
Fibrogel
How do bulk forming laxatives work
polysaccharide polymers which are not broken down in the upper GI tract.
They increase stool volume.
This activates the stretch relfex which stimulates peristalsis.
What is an example of Osmotic laxatives?
Lactulose
How do Osmotic laxatives work?
Solutes which are not absorbed producing an osmotic gradient within the bowel.
Water moves into the lumen and speeds the transfer of gut contents through the small intestine
This softens the stool and increases the distension of the lumen activating the stretch relfex which stimulates peristalsis.
What is an example of Stimulant Laxatives
Senna
How do stimulant laxatives work?
increase electrolyte and water secretion by the GI mucosa and to increase peristalsis.
Senna is an anthroquinone stimulant laxative which directly stimulates the myenteric plexus leading to increased peristalsis and defecation.
When would you specifically use lactulose?
In hepatic encephalopathy
What are side effects of laxatives?
Abdominal distension and cramps
Flatulence and Diarrhoea
Electrolyte disturbances!!
What are contraindications to Laxatives
Lactulose in patients who are lactose intolerant
Avoid in intestinal obstruction or perforation. In severe inflammatory bowel disease and severe
dehydration
What is important to communicate to patients?
Explain to patients that they should drink plenty of fluids while taking laxatives to avoid dehydration and/or bowel obstruction.
Patients should also maintain a healthy diet that includes fiber, fruit and vegetables.
Osmotic and bulk-forming laxatives won’t work immediately, take 2-3 days to reach their full effect.
