GI cards Flashcards Preview

Smart Revision > GI cards > Flashcards

Flashcards in GI cards Deck (10)
Loading flashcards...
1

Bulk Laxatives

Examples
Ispaghula
Bran
Methylcellulose

Route of Administration
Oral

Indications
Constipation, particularly when hard stools are present

Contraindications
Dysphagia
Intestinal obstruction (Adhesions, ulceration)
Colonic atony
Faecal impaction

Mechanism of Action
Increases the volume of the non-absorbable solid residue in the gut, distending the colon and stimulating peristaltic movement.

Adverse Drug Reactions
Flatulence
Abdominal distension
GI obstruction

Therapeutic Notes
A normal fluid intake is essential
Clinical effects may take several days to develop

2

Faecal Softeners

Examples
Arachis Oil
Glycerol

Route of Administration
Arachis Oil – Enema
Glycerol – Suppository

Indications
Constipation
Faecal impaction
Haemorrhoids
Anal fissures

Contraindications
Children less than 3 years old

Mechanism of Action
Lubricate and soften stools

Therapeutic Notes
Safe, but not always effective
Relatively slow to take effect

3

Osmotic Laxatives

Examples
Lactulose
Magnesium and Sodium Salts
Movicol

Route of Administration
Lactulose – Oral
Magnesium and Sodium Salts – Rectal
Movicol – Orally with fluid (powder)

Indications
Constipation
Lactulose - Liver failure (reduced production of ammonia)

Contraindications
Intestinal obstruction

Mechanism of Action
Increase water content of the bowel via osmosis
Lactulose – Disaccharide (galactose/fructose) that cannot be hydrolysed by digestive enzymes. The fermentation of lactulose by colonic bacteria gives acetic and lactic acid. This has an osmotic effect

Adverse Drug Reactions
Flatulence
Cramps
Abdominal discomfort
Caution required to prevent intestinal obstruction

Therapeutic Notes
Magnesium and Sodium act quickly and are quite severe, so should be reserved for ‘resistant’ constipation if urgent relief is required
Lactulose takes 48 hours to work
Movicol takes 2-4 days to get relief

4

Irritant / Stimulant Laxatives

Examples
Anthraquinone Group
Senna
Danthron
Bisacodyl

Route of Administration
Oral

Indications
Constipation and bowel evacuation prior to medical/surgical procedures

Contraindications
Intestinal obstruction

Mechanism of Action
Increase gastrointestinal peristalsis and water and electrolyte secretion by the mucosa. Possibly by excitation of sensory enteric nerves.

Adverse Drug Reactions
Colonic atony (thus constipation)
Hypokalaemia (Changing electrolyte balance in the gut)

Therapeutic Notes
Anthraquinone group is the most frequently used.
Senna can be bought O.T.C. (Senokot)
Abuse can be detected via Melanosis Coli (pigmentation of bowel wall)

5

Anti-Motility Antidiarrhoeals

Examples
Codeine (opiate analgesic)
Imodium (opiate analogue)

Contraindications
Inflammatory Bowel Disease – Toxic Megacolon

Mechanism of Action
Act on opioid receptors in the bowel
Reduce motility (increase time for fluid reabsorption)
Increase anal tone and reduce sensory defecation reflex

Adverse Drug Reactions
Nausea, vomiting, abdominal cramps, constipation drowsiness

Therapeutic Notes
Imodium is 40 times more potent than Morphine as an antidiarrhoeal agent, and penetrates the CNS poorly

6

Bulk Forming Antidiarrhoeals

Examples
Ispaghula

Route of Administration
Oral

Indications
Particularly useful for patients with IBS and those with ileostomy

Contraindications
Intestinal obstruction

Mechanism of Action
A relatively small amount of faecal fluid (10-20ml) influences composition. Bulk forming antidiarrhoeals absorb this fluid.

7

Dopamine (D2) Receptor Antagonists (Anti Emetics)

Examples
Domperidone
Metoclopramide
Phenothiazines

Route of Administration
Oral
Rectal (extensive 1st pass metabolism)

Indications
Acute nausea/vomiting
Especially induced by L-DOPA or dopamine agonists

Mechanism of Action
Acts on the Postrema on the floor of the 4th ventricle
Acts on the stomach to increase the rate of gastric emptying

Adverse Drug Reactions
Stimulates prolactin release
Metoclopramide – extra-pyramidal reactions (dystonia) occur in 1%, therefore is avoided in Parkinson’s disease

8

Examples
Domperidone
Metoclopramide
Phenothiazines

Route of Administration
Oral
Rectal (extensive 1st pass metabolism)

Indications
Acute nausea/vomiting
Especially induced by L-DOPA or dopamine agonists

Mechanism of Action
Acts on the Postrema on the floor of the 4th ventricle
Acts on the stomach to increase the rate of gastric emptying

Adverse Drug Reactions
Stimulates prolactin release
Metoclopramide – extra-pyramidal reactions (dystonia) occur in 1%, therefore is avoided in Parkinson’s disease

Examples
Ondansetron
Granisetron

Route of Administration
Oral, IV or IM

Indications
In high doses in radiation sickness, chemotherapy sickness, post operatively

Mechanism of Action
5-HT is released into the gut, reducing Vagus activity, therefore effective at deactivating the vomiting centre (the Postrema on the floor of the 4th ventricle)
Blocks Serotonin receptors in Chemoreceptor Trigger Zone

Adverse Drug Reactions
Headaches, constipation, flushing

Drug-Drug Interactions
Anti-Emetic effect can be enhanced by a single dose of a corticosteroid

9

Anti-Muscarinics (Anti Emetic)

Examples
Hyoscine

Route of Administration
Oral or patch

Indications
Motion sickness

Mechanism of Action
Direct antagonist of muscarinic cholinergic receptors (M1)

Adverse Drug Reactions
Systemic anti-cholinergic effects, bradycardia

10

Histamine H1 Receptor Antagonists (Anti Emetic)

Examples
Cyclizine

Route of Administration
Oral, IV or IM

Indications
Acute nausea and vomiting

Contraindications
Myocardial ischaemia

Mechanism of Action
Antagonises H1 receptors

Adverse Drug Reactions
Can cause QT prolongation
Crosses the BBB – Sedative effect