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5 - Pharmacology > Laxatives and Anti-diarrhoeals > Flashcards

Laxatives and Anti-diarrhoeals Flashcards

1
Q

Give the different types of laxatives

A

Bulk laxativeOsmotic laxativesFaecal softenersIrritant/stimulant laxatives

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2
Q

Mechanism of bulk laxatives

A

Increase volume of non-absorbable solid residue in gut to stimulate gut distension. This stimulates peristalsis

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3
Q

Give some examples of bulk laxatives

A

BranIspaghulaMethylcellulose

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4
Q

ADRs of bulk laxatives

A

Gut obstructionFlatulenceAbdominal distention

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5
Q

Give some examples of faecal softeners and how they would be given

A

Arachis oil - enemaGlycerol - suppository

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6
Q

When would you give faecal softeners?

A

ConstipationAnal fissuresHaemmorrhoidsFaecal impaction

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7
Q

Mechanism for faecal softeners

A

Loosen and soften stools

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8
Q

Give some examples of osmotic laxatives

A

LactuloseSodium and magnesium saltsMovicol

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9
Q

Give the routes of administration for the osmotic laxatives

A

Lactulose = oralMg & Na salts = rectalMovicol = orally with fluid as is a powder

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10
Q

Mechanism for osmotic laxatives

A

Increase the water content of the bowel via osmosis

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11
Q

Give the specific mechanism for lactulose

A

Lactulose is a disaccharide that cannot be hydrolysed by digestive enzymes. The fermentation of lactulose by colonic bacteria gives rise to acetic and lactic acid which have an osmotic effect.

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12
Q

ADRs for osmotic laxatives

A

FlatulenceCrampsAbdominal discomfortNeed to take care to prevent intestinal obstruction

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13
Q

How long does each form of osmotic laxative take to work?

A

Mg and N- work quite quickly and are quite severeLactulose = 48 hoursMovicol = 2-4 days

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14
Q

Give some examples of irritant laxatives

A

SennaDanthronBisacodyl

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15
Q

Mechanism of irritant laxatives

A

Increase GI peristalsis and water and electrolyte secretion by the mucosa. Potentially is due to excitation of sensory enteric nerves.

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16
Q

ADRs of irritant laxatives

A

HypokalaemiaColonic atony and therefore contipation

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17
Q

How can you detect abuse of irritant laxatives?

A

Melanosis cell which is pigmentation of the bowel wall.

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18
Q

Give some causes of diarrhoea

A

InfectionsToxinsDrugsChronic diseaseAnxiety

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19
Q

How do you treat diarrhoea generally?

A

Treat the symptoms, not the cause. Give appropriate fluid and electrolyte balance.

20
Q

What are the general classes of antidiarrhoeals?

A

Anti-motility antidiarrhoealsBulk forming antidiarrhoeals

21
Q

Examples of anti-motility antidiarrhoeals

A

Codeine - opiate analgesicImodium - opiate analogue

22
Q

Mechanism of anti-motility antidiarrhoeals

A

Act on opioid receptors in the bowel to reduce the gut motility. They also increase anal tone and reduce the sensory defecation reflex.

23
Q

ADRs of anti-motility diarrhoeals

A

NauseaVomitingAbdominal crampsConstipationDrowsiness

24
Q

When would you not give an anti-motility antidiarrhoeal?

A

With inflammatory bowel disease as it can give rise to toxic megacolon

25
Q

Give some examples of bulk-forming antidiarrhoeals

A

Isphagula

26
Q

Mechanism for bulk forming antidiarrhoeals

A

Absorb faecal fluid to increase bulk, therefore decreasing diarrhoea.

27
Q

Give the main features of irritable bowel syndrome

A

Abdominal painDiscomfortBloatingAlteration of bowel habits

28
Q

How would you treat IBS?

A

Mebeverine- affects colonic hypermobility by decreasing the spasming of intestinal muscles which is the main symptom complained about with IBS

29
Q

Describe the process of emesis

A

Pyloric sphincter closes, cardia and oesophagus relax. Gastric contents are propelled by contraction of the abdominal wall and diaphragm. Glottis closes, soft palate elevates to prevent aspiration of vomit.

30
Q

When is there a higher rate of aspiration of vomit?

A

Alcohol intoxicationCranial nerve lesion

31
Q

How is the process of vomiting controlled?

A

Stimulation of the Postrema, which is found on the floor of the 4th ventricle. This is where the vomiting centre is found. It detects toxins in the blood and then stimulates vomiting. ORStimulation of the vestibular apparatus (motion sickness) which goes on to stimulate the medullry centre

32
Q

Give some examples of anti-emetics

A

Dopamine receptor antagonistsSerotonin antagonistsAnti-muscarinicsHistamine antagonistsCannabinoidsBenzodiazepines

33
Q

Give some examples of D2 antagonists

A

DomperiddoneMetoclopramidePhenothiazines

34
Q

Mechanism for D2 antagonists

A

Acts on postrema and stomach to inhibits the rate of gastric emptying

35
Q

ADRs of D2 antagonists

A

Stimulates prolactin releaseMetoclopramide - extra-pyramidal side effects, so avoid in Parkinsons

36
Q

Give some examples of serotonin antagonists

A

OndansetronGranisetron

37
Q

Mechanism for serotonin antagonists

A

Reduces release of 5HT from the guts, as it acts on the vagus nerve. This helps to deactivate the postrema. Also blocks serotonin receptors in the chemoreceptor trigger zone.

38
Q

ADRs of serotonin antagonists

A

HeadachesConstipationFlushing

39
Q

Give a drug-drug interaction with serotonin antagonists

A

Anti-emetic effect can be enhanced by a single dose of corticosteroid

40
Q

Give some examples of anti-muscarinics

A

Hyoscine

41
Q

Mechanism for anti-muscarinics

A

Directly antagonise the muscarinic cholinergic M1 receptors which stimulate emesis

42
Q

ADRs for anti-cholinergics

A

Systemic anti-cholinergic effectsBradycardia

43
Q

Give some examples of histamine antagonists

A

Cyclizine

44
Q

Mechanism for histamine antagonists

A

Antagonise H1 receptors

45
Q

ADRs of histamine antagonists

A

Prolong QT intervalCross the BBB and have a sedative effect.

5 - Pharmacology (17 decks)

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