GI BLOCK DRUGS

Question 1

Magnesium trisilicate MOA

Answer 1

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

Question 2

Magnesium trisilicate side effects and contraindications

Answer 2

Can be nephrotoxic.
Side effects include diarrhoea and nephrolithiasis (long term use).
Contraindications: hypophosphatemia

Question 3

Aluminium/magnesium mixtures

Answer 3

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

Question 4

Alginates MOA

Answer 4

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

Question 5

Alginates side effects

Answer 5

Can be nephrotoxic.
Side effects include diarrhoea and nephrolithiasis (long term use).

Question 6

Ranitidine

Answer 6

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

Question 7

Lansoprazole vs omeprazole

Answer 7

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.

Question 8

Codeine phosphate

Answer 8

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.

Question 9

Loperamide

Answer 9

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

Question 10

Bulk-forming laxatives

Answer 10

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

Question 11

Osmotic laxatives

Answer 11

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.

Question 12

Stimulant laxatives.

Answer 12

senna (prolonged use can cause hypokalemia)
sodium picosulfate (can be used on children)
bisacodyl

Question 13

Faecal softeners

Answer 13

docusate sodium co-danthrusate

Question 14

which laxatives are safe in pregnancy

Answer 14

Senna, magnesium salts and docusate

Question 15

laxatives which are suitable for the elderly or for the terminally ill with opioid-induced constipation.

Answer 15

Bisacodyl, co-danthramer and co-danthrusate

Question 16

For opioid-induced constipation when other laxatives are ineffective, whats used

Answer 16

the peripheral opioid receptor antagonist methylnaltrexone can be used.

Question 17

For people in whom neurological disease affecting bowel motility is the cause of constipation whats used

Answer 17

a faecal softener should be used, with regular enemas or rectal washouts.

Question 18

mesalazine

Answer 18

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.

Question 19

Hydrocortisone
Prednisolone
Budesonide (ibd specific)

Answer 19

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

Question 20

Azathioprine

Answer 20

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.

Question 21

azathioprine drug reactions

Answer 21

Two serious drug interactions with azathioprine or 6-MP are allopurinol and febuxostat, which slow the elimination of 6-MP by inhibiting xanthine oxidase.

Question 22

Infliximab

Answer 22

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.

Question 23

infliximab infusion reaction

Answer 23

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.

Question 24

Adalimumab

Answer 24

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

Question 25

Hyoscine butyl bromide:

Answer 25

Aka Buscopan. Used to receive stomach cramps and IBS. It blocks the neuro transmitter acetylcholine by binding with muscarinic acetylcholine receptors, which in turn prevents nervous impulses to the parasympathetic nervous system.
Side effects include Constipation; dizziness; drowsiness; dry mouth; dyspepsia; flushing; headache; nausea; palpitations; skin reactions; tachycardia; urinary disorders; vision disorders; vomiting.

Question 26

Mebeverine:

Answer 26

Mebeverine is an antispasmodic used for the symptomatic treatment of stomach pain and spasms associated with irritable bowel syndrome.
Contraindications include paralytic ileus. Side effects include Angioedema; face oedema; skin reactions.

Question 27

Peppermint oil

Answer 27

It is proposed that peppermint oil relaxes gastrointestinal smooth muscle and attenuates contractile responses by reducing the influx of extracellular calcium ions. (antispasmodic)
Side effects include: Ataxia; bradycardia; gastrointestinal discomfort; gastroesophageal reflux disease; headache; nausea; paraesthesia; rash erythematous; tremor; vomiting.

Question 28

Nystatin

Answer 28

effective against a wide variety of yeasts and yeast-like fungi, including Candida albicans, C. parapsilosis, C. tropicalis etc. Action is via binding to ergosterol in fungal cell membranes. This binding to ergosterol causes the formation of pores in the membrane, leading to potassium and other cellular constituents leakage causing cell death.
Side effects include Abdominal distress; angioedema; diarrhoea; face oedema; nausea; sensitisation; skin reactions; Stevens-Johnson syndrome; vomiting.

Question 29

Fluconazole

Answer 29

used to treat vaginal candidiasis. Its mechanism of action is the inhibition of 14-α demethylase, a cytochrome P-450 enzyme that converts lanosterol to ergosterol, an important component of fungal cell membranes. This inhibition leads to increased membrane permeability and possibly disruption of membrane bound enzymes.
Side effects include Common or very common- Diarrhoea; gastrointestinal discomfort; headache; nausea; skin reactions; vomiting.

Question 30

Metronidazole

Answer 30

Metronidazole is an antibiotic that is used to treat bacterial infections of the vagina, stomach, liver, skin, joints, brain and spinal cord, lungs, heart, or bloodstream.
Metronidazole is also used to treat trichomoniasis, a sexually transmitted disease caused by a parasite. Usually both sexual partners are treated at the same time, even if one has no symptoms.
Side effects include With intravenous use-Dry mouth; myalgia; nausea; oral disorders; taste metallic; vomiting. With topical use-Skin reactions. With vaginal use-Pelvic discomfort; vulvovaginal candidiasis; vulvovaginal disorders.

Question 31

Vancomycin

Answer 31

Vancomycin is often reserved as the “drug of last resort”, used only after other antibiotics have failed. Peptidoglycan inhibitor. In addition, vancomycin alters bacterial-cell-membrane permeability and RNA synthesis. Contraindications With intravenous use-Previous hearing loss. Some side effects Agranulocytosis; dizziness; drug fever; eosinophilia; hypersensitivity; nausea; nephritis tubulointerstitial; neutropenia, renal failure; severe cutaneous adverse reactions (SCARs); skin reactions; thrombocytopenia; tinnitus (discontinue); vasculitis; vertigo.

Question 32

antibiotics used to treat c difficile

Answer 32

metronidazole or vancomycin as last resort