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Human Diseases > 19.2 Gastrointestinal drugs > Flashcards

19.2 Gastrointestinal drugs Flashcards

1
Q

Which first line medication is used to treat gastro-oesophageal reflux disease?

A

Proton pump inhibitors e.g. omperazole, lansoprazole

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2
Q

Give examples of drugs used to treat GORD, dyspepsia, peptic ulcers and upper gastrointestinal haemorrhages.

A
  • Alkali alginate mixtures e.g. gaviscon
  • H2 receptor antagonists e.g. ranitidine, cimetidine
  • PPIs e.g. omeprazole
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3
Q

Describe the action of H2 receptor antagonists.

A
  • Antagonise (block) the H2 receptor on the gastric parietal cells
  • Reduces gastric acid secretion
  • Less effective than PPIs
  • Preferable for long term use
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4
Q

Do H2 receptor inhibitors interact with other drugs?

A

Yes, they interfere with a range of drugs.
E.g. Cimetidine interacts with warfarin, erythromycin, antifungals, carbamazepine

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5
Q

Give examples of proton pump inhibitors.

A
  • Esomeprazole
  • Lansoprazole
  • Omperazole
  • Pantoprazole
  • Rabeprazole
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6
Q

How do H2 receptor antagonists act on the gastric parietal cells?

A

They block histamine 2 from binding to the H2 receptor of the parietal cell, thus preventing the production of cAMP and therefore preventing the function of the proton pump.

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7
Q

How do proton pump inhibitors act on gastric parietal cells?

A

Irreversibly inhibit the proton pump H/K-ATPase thus preventing acid secretion.

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8
Q

Describe the main features of PPIs.

A
  • Prodrugs which require gastric acid for their conversion
  • Good oral bioavailability
  • Short plasma half life, approx.1 hour
  • Duration of action is longer than 1 hour as they covalently bond causing irreversible inhibition of the proton pump - duration of acid suppression = 48 hours
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9
Q

Which enzymes metabolise PPIs?

A
  • CYP2C19
  • 3A4
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10
Q

What are the possible adverse side effects of PPIs?

A
  • Hyponatraemia (low sodium)
  • Fractures
  • C.difficile infection
  • Hypomagnesaemia
  • Gastric cancers
  • B12 deficiency
  • Acute intestinal nephritis
  • Pneumonia
  • Cardiovascular disease
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11
Q

Which drug does omeprazole interact with?

A

Omeprazole interacts with clopidogrel, reducing its antiplatelet effects

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12
Q

What is H. pylori?

A

Helicobacter Pylori is a bacteria which infects the stomach, it is a major risk factor for peptic ulcers and stomach cancer.

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13
Q

How can we test for H. pylori?

A
  • Carbon-13 urea breath test
  • Stool antigen test
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14
Q

How is H. pylori treated?

A
  • 7 day, twice daily course of treatment with: a PPI, amoxicillin and clarithomycin or metronidazole
  • Pencillin allergy: 7-day, twice daily course of treatment with a PPI and clarithromycin and metronidazole
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15
Q

How should patients take PPIs?

A
  • Prescribe the lowest effective dose for the minimum period of time
  • Advise patients to take them 30-60 minutes before breakfast
  • Risk of rebound hypersecretion on discontinuation for possibly 2-4 weeks after
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16
Q

Name 6 anti-emetics.

A
  • Histamine-1 receptor antagonists
  • Dopamine-2 receptor antagonists
  • Muscarinic cholinergic receptor antagonists
  • 5HT-3 receptor antagonists
  • Neurokinin receptor antagonists
  • Cannabinoids
17
Q

Give examples of histamine-1 receptor antagonists.

A
  • Cyclizine
  • Cinnarizine
18
Q

Give examples of dopamine-2 receptor antagonists.

A
  • Metoclopramide
  • Phenothiazines
19
Q

Give an example of a muscarinic cholinergic receptor antagonist.

A

Hyoscine (anti-motion sickness)

20
Q

Give an example of a 5HT-3 receptor antagonist.

A

Ondansetron (for severely emetogenic chemotherapy), risk of cleft lip/palate in pregnancy.

21
Q

Give an example of a neurokinin receptor antagonist.

A

Aprepitant

22
Q

Give an example of a cannabinoid.

A

Nabilone

23
Q

What are the 3 major modes of actions for medicines used on the GI tract to manage constipation and diarrhoea?

A
  • Laxatives and purgatives: affect fluid absorption and secretion
  • Drugs that increase gastric motility: increase smooth muscle motility
  • Drugs that decrease gastric motility: decrease smooth muscle motility
24
Q

Non-drug management of constipation.

A
  • Increase dietary fibre
  • Adequate fluid intake
25
Q

What are the main medicines used for the management of constipation?

A
  • Bulk forming laxatives e.g. methylcellulose
  • Stimulants e.g. senna, bisacodyl
  • Faecal softeners
  • Osmotic laxatives e.g. lactulose, macrogol, magnesium hydroxide
  • Bowel cleansing for colonoscopy or bowel radiology investigation
26
Q

Describe diarrhoea.

A
  • Frequent passage of loose stools
  • Increased GI motility
  • Increased secretions
  • Reduced absorption
27
Q

What are the possible causes of diarrhoea?

A
  • Infection e.g. norovirus, campylobacter, salmonella
  • Toxins
  • Drugs
  • Anxiety
28
Q

How is diarrhoea managed?

A
  • Fluids and electrolyte replacement e.g. dioralyte
  • Cautious use of anti-motility agents
  • Possible antimicrobial treatments
29
Q

What agents decrease GI motility?

A
  • Opiates: increase tone but diminish propulsive activity, act on pyloric, ileocecal and anal sphincters e.g. codeine, loperamide
  • Adsorbants: absorb toxic substances that cause infective diarrhoea e.g. Kaolin, pectin
30
Q

Describe irritable bowel syndrome.

A
  • Has no demonstratable pathology
  • Could be associated with depression and anxiety
31
Q

How is IBS managed?

A
  • Anti-motility drugs for diarrhoea
  • Laxatives for constipation (avoid lactulose)
  • Antispasmodics and peppermint oil for pain and diarrhoea
32
Q

What diseases does IBD cover?

A

Crohn’s disease and ulcerative colitis

33
Q

Give examples of steroids used to treat IBD.

A
  • Budesonide
  • Beclometasone
34
Q

Give examples of aminosalicylates used to treat IBD.

A
  • Mesalazine
  • Sulfasalazine
35
Q

Give examples of drugs used to treat IBD which affect the immune response.

A
  • Methotrexate
  • Azathioprine
  • Cytokine modulators: inflixamab and adalimumab
36
Q

What precautions need to be taken if a patient is prescribed infliximab or adalimumab?

A
  • Pre-treatment screening for TB
  • Regular blood tests
  • Patients provided with an alert card
37
Q

What are the risk factors for gall stones?

A
  • Female, especially if they have had children or are on high dose oestrogen
  • Over 40
  • Raised BMI
  • Rapid weight loss
  • Crohn’s/IBS
  • Cirrhosis / Primary sclerosing cholangitis / Obstetric choletstasis
  • Family history
38
Q

What is cholecystitis?

A

Inflammation of the gall bladder, usually caused by a gallstone blocking the cystic duct. Can also be caused by a bacterial infection.
Treated with antibiotics (if caused by infection) and elective surgery.

39
Q

What is biliary colic?

A

Pain in the abdomen as a result of obstruction in the cystic duct or common bile duct.
Managed with pethidine (an opioid).

Human Diseases (47 decks)

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