GI BLOCK DRUGS Flashcards
Magnesium trisilicate MOA
Magnesium trisilicate works by increasing the pH of gastric juice via a neutralisation reaction. It also precipitates colloidal silica, which can coat gastrointestinal mucosa conferring further protection.
Used for dyspepsia and GORD.
Present in gaviscon
Magnesium trisilicate side effects and contraindications
Can be nephrotoxic.
Side effects include diarrhoea and nephrolithiasis (long term use).
Contraindications: hypophosphatemia
Aluminium/magnesium mixtures
Co-magaldrox is a mixture of aluminium hydroxide and magnesium hydroxide
Used for dyspepsia and GORD.
Present in Maalox or Mucogel.
Can be nephrotoxic.
Side effects include constipation diarrhoea and abdominal pain
Alginates MOA
When sodium alginate mixes with the acid in your stomach, it forms a “raft” that floats on the top of your stomach contents. This creates a physical barrier over your stomach contents, which stops acid reflux. Treatment with an alginate product can also help reduce the amount of pepsin and bile in your stomach contents – other digestive acids that can contribute to reflux symptoms.
Used for dyspepsia and GORD. Present in Gaviscon
Alginates side effects
Can be nephrotoxic.
Side effects include diarrhoea and nephrolithiasis (long term use).
Ranitidine
Stops histamine binding to h2 receptors so gastric acid not released.
Used for dyspepsia, GORD, peptic ulcers, prophylaxis of NSAID associated peptic ulceration.
H2-receptor antagonists might mask symptoms of gastric cancer; particular care is required in patients presenting with ‘alarm features’ in such cases gastric malignancy should be ruled out before treatment
Ranitidine is not currently available in the UK or globally. It has been discontinued as a precaution because it may contain a small amount of an impurity that has been linked to an increased risk of cancer in animals
Lansoprazole vs omeprazole
Proton pump inhibitors inhibit gastric acid secretion by blocking the hydrogen-potassium ATP pump gastric parietal cell. Used for dyspepsia, GORD, oesophagitis, peptic ulceration, prophylaxis of NSAID associated peptic ulceration, H. pylori eradication.
Avoided in pregnancy. Slightly hepatotoxic.
Omeprazole is the same as above but safe in pregnancy.
Codeine phosphate
Codeine is a painkiller that is part of a group of medicines called opiates. It’s used to treat pain, for example, after an operation or an injury. It’s also used for ongoing pain when other analgesics eg ibuprofen have not worked. Codeine is also used to treat diarrhoea as a side effect is constipation.
Contraindications include Acute respiratory depression; comatose patients; head injury/raised intracranial pressure (opioid analgesics interfere with pupillary responses vital for neurological assessment) risk of paralytic ileus. Acute ulcerative colitis.
Loperamide
non-selective calcium channel blocker which also binds to opioid mu-receptors in the myenteric plexus large intestine.
used for the control and symptomatic relief of acute nonspecific diarrhoea and of chronic diarrhoea associated with inflammatory bowel disease.
Contra-indications Include Active ulcerative colitis; antibiotic-associated colitis; bacterial enterocolitis; conditions where abdominal distension develops; conditions where inhibition of peristalsis should be avoided
Bulk-forming laxatives
Ispaghula (psyllium) husk: aka fybogel-granules you mix with water. Specific side effects include itchy eyes, nose or skin.
Methylcellulose: powder you mix with water
Osmotic laxatives
Lactulose: synthetic sugar, is useful specifically to treat constipation associated with hepatic encephalopathy.
Macrogols: powder you mix with water. High sodium content. Contraindications: Ileus; intestinal obstruction; intestinal perforation; risk of intestinal perforation; severe inflammatory bowel disease; toxic megacolon.
Stimulant laxatives.
senna (prolonged use can cause hypokalemia)
sodium picosulfate (can be used on children)
bisacodyl
Faecal softeners
docusate sodium co-danthrusate
which laxatives are safe in pregnancy
Senna, magnesium salts and docusate
laxatives which are suitable for the elderly or for the terminally ill with opioid-induced constipation.
Bisacodyl, co-danthramer and co-danthrusate
For opioid-induced constipation when other laxatives are ineffective, whats used
the peripheral opioid receptor antagonist methylnaltrexone can be used.
For people in whom neurological disease affecting bowel motility is the cause of constipation whats used
a faecal softener should be used, with regular enemas or rectal washouts.
mesalazine
usually first line anti-inflammatory drug used for IBD not used in people with clotting problems. Side effects include headache and can occasionally worsen ulcerative colitis.
Hydrocortisone
Prednisolone
Budesonide (ibd specific)
The short term effects of corticosteroids are decreased vasodilation and permeability of capillaries, as well as decreased leukocyte migration to sites of inflammation
Unlike other forms of anti-inflammatory drugs, corticosteroids are not used long-term to help patients to stay in remission. One of the reasons for this is that corticosteroids are not able to heal the damage to the lining of the intestines (called the “mucosa”) that IBD can cause. Instead, corticosteroid treatment for IBD is focused on:
* Short-term treatment to help relieve moderate or severe symptom flare-ups
* Helping the patient to enter remission more quickly
Azathioprine
Azathioprine’s mechanism of action is not entirely understood but it may be related to inhibition of purine synthesis, along with inhibition of B and T cells.
Common or very common- Bone marrow depression (dose-related); increased risk of infection; leucopenia; pancreatitis; thrombocytopenia.
Uncommon- Anaemia; hepatic disorders; hypersensitivity.
Used to treat Crohn’s disease.
azathioprine drug reactions
Two serious drug interactions with azathioprine or 6-MP are allopurinol and febuxostat, which slow the elimination of 6-MP by inhibiting xanthine oxidase.
Infliximab
Infliximab is a chimeric monoclonal which has a high specificity for and affinity to tumor necrosis factor (TNF)-alpha. Infliximab neutralizes the biologic activity of TNF-alpha by inhibiting binding to its receptors. Infliximab can also stimulate apoptosis of activated lymphocytes in the gut mucosa. Elevated TNFα levels have been found in involved tissues/fluids of patients with rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, plaque psoriasis, Crohn disease and ulcerative colitis. Contraindications: Moderate or severe heart failure; severe infections.
The most common side effects of infliximab include: respiratory infections, such as sinus infections and sore throat, headache, coughing, and stomach pain. and increased susceptibility to infections such as tuberculosis.
infliximab infusion reaction
Infusion reactions can happen up to 2 hours after your infusion of infliximab.
Symptoms of infusion reactions may include: fever, chills, chest pain, low blood pressure or high blood pressure, shortness of breath, rash, itching.
Adalimumab
Adalimumab is a recombinant fully human monoclonal antibody that binds to TNF-alpha, thereby interfering with binding to TNF-alpha receptor sites and subsequent cytokine-driven inflammatory processes. Contraindications, cautions and side effects all same as infliximab
