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A13THP @ UoN > Lower GI Pharmacology > Flashcards

Lower GI Pharmacology Flashcards

1
Q

What is the clinical definition of Diarrhoea?

A

Frequent (>3/day) watery/soft stools OR 200g stool/day

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2
Q

What are the major infective causes of diarrhoea?

A

Rotavirus
Invasive bacteria
Adhesive enterotoxigenic bacteria

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3
Q

How does Rotavirus lead to diarrhoea?

A

Damages small bowel villi

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4
Q

How do Invasive bacteria lead to diarrhoea?

A

Damage epithelium

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5
Q

How do adhesive enterotoxigenic bacteria lead to diarrhoea?

A

Adhere to brush border

Increase cAMP - Cl/Na secretion, followed by water

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6
Q

What are the common drug related causes of Diarrhoea?

A 
Antibiotics - superinfection
Orlistat - pancreatic lipase inhibitor
Misoprostol - increases cAMP
PPIs - infection
Digoxin toxicity, acarbose, metformin, iron salts
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7
Q

What is ORT?

A

Oral rehydration therapy

Isotonic solution of electrolytes with glucose

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8
Q

Why is glucose needed in an ORT?

A

Allows transport of Na via a symporter

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9
Q

How do antibiotics lead to Diarrhoea?

A

Suppress normal gut flora

Leads to superinfection w/ normally dormant bacterium

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10
Q

When should antibiotics be used to treat Diarrhoea?

A

Infections mostly viral, often self-limiting
Use when causative bacteria identified
Use Ciprofloxacin empirally for traveller’s diarrhoea

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11
Q

What are the two most common types of antimotility agents?

A

Opioids

Anti-muscarinics

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12
Q

How do opioids lead to antimotility?

A

Presynaptic inhibition (u-opioid receptors) of AcH release
Reduces motility
Promotes reabsorption of water

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13
Q

What are opioids used for?

A

Symptomatic relief of diarrhoea

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14
Q

What are the possible negative effects of treatment with opioids?

A

Reduce clearance of infective organisms - prolong infection

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15
Q

What are the two most commonly prescribed opioids?

A

Loperamide - retained largely in the gut, doesn’t penetrate BBB, enterohepatic cycling
Codeine - analgesia

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16
Q

How do Alpha-2 adrenoceptor agonists work?

A

Agonise a2-receptors - causes constipation

CLONIDINE

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17
Q

How do antimuscarininc agents work?

A

Antagonise muscarininc receptors
Decreased activity of PNS - constipation
DICYCLOVERINE

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18
Q

What effect do TCAs have on diarrhoea?

A

Antagonise muscarinic receptors

Constipation as a side effect

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19
Q

Define constipation

A

Altered bowel habits

<3 motions/week

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20
Q

How is constipation treated?

A

Balanced diet w/ roughage

Avoid causative drugs

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21
Q

How do osmotic laxatives work?

A

Enter colon - converted to lactic/acetic acid (bacteria) - raises fluid volume osmotoically
LACTULOSE

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22
Q

What non-osmotic laxatives are available?

A

Magnesium
Bulking agents
Stimulant laxatives

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23
Q

How does Magnesium work?

A

Osmotic effect

Mg2+ release cholecystokinin - increases GI motility

24
Q

How do bulking agents work?

A

Increase bulk of faeces, trigger release
ISPAGHULA
METHYLCELLULOSE

25
Q

How do stimulant laxatives work?

A

Senna extracts - enter colon - metabolised to anthracene derivates - stimulate GI activity
Dantron - irritant

26
Q

What is Irritable Bowel Syndrome?

A

Long standing disorder (12/52)
Pain/bloating relieved by defecation
Episodes of diarrhoea/constipation

27
Q

What are the main pharmacological treatments for IBS?

A

Lactulose/Loperamide for symptoms
Antispasmodic agents
Amitryptyline (TCA)

28
Q

How do antispasmodic agents work?

A

Antimuscarinics - inhibit PNS

Mebeverine - direct relaxant of GI sm, phosphodiesterase inhibitor

29
Q

How does Amitryptyline work?

A

Antimuscarinic effects

Alters sensitivity of sensory ner

30
Q

What is Inflammatory Bowel Disease?

A

Ulcerative Colitis AND Chron’s Disease

31
Q

Describe UC/Chron’s

A

Distinct inflammatory conditions
Relapsing/remitting courses
Unclear causes (genetics, microbial, environmental)

32
Q

What are the clinical features of UC/Chron’s?

A 
Diarrhoea
Faecal incontinence
Rectal bleeding/bloody diarrhoea
Passing of mucus
Cramping pains
Weight loss
Mouth ulcers + anal skin tags (Chron's)
33
Q

What are the complications of Chron’s disease?

A

Malabsorption

Folate/iron deficiencies - anaemias

34
Q

What is the main complication of Ulcerative Colitis?

A

Iron deficiency anaemia

35
Q

What are the shared complications of IBD?

A

Arthritis
Iritis
Uveitis
Thromboembolism

36
Q

What are the defining characteristics of UC?

A

Inflammation of rectum, spreads to colon

Superficial, affecting mucosa

37
Q

What are the defining characteristics of Chron’s?

A

May affect any part of GI, usually Ileum/Colon

Activation of T-lymphocytes - transmural inflammation - fistulae

38
Q

What is the mainstay treatment for UC?

A

5-Aminosalicylates

39
Q

What are the three main 5-Aminosalicylates?

A

Sulphasalazine - metabolised to 5-ASA (gut flora)
Mesalazine - pH change produces 5-ASA
5-ASA

40
Q

How does 5-ASA have its effect?

A

Inhibits leukotriene/prostanoid formation
Scavenges free radicals
Decreases neutrophil chemotaxis

41
Q

What are corticosteroids used for?

A

To induce remission in IBD?

42
Q

What are the main corticosteroids?

A

Prednisolone

Budenoside - poorly absorbed so fewer s/e

43
Q

How do corticosteroids work?

A

Anti-inflammatory, immunosuppressive

44
Q

What immunosuppressants are used to treat Chron’s?

A

Azathioprine
Cyclosporine
Methotrexate

45
Q

What is Inflixmab?

A

Monoclonal antibody to TNF-a used to treat severe Chron’s

46
Q

What are the ADRs associated with 5-ASAs?

A

Rashes
Headaches
Diarrhoea

47
Q

What is the specific ADR associated with Mesalazine?

A

Blood dyscrasia (abnormal materials in blood)

  • sore throats
  • fevers
  • easy brusing/bleeding
48
Q

What dietary changes can be used to treat IBD?

A

Avoid fatty food
Avoid bolus foods (nuts/corn/fruit)
Fish oils/probiotic recommened
Amino acids/proteins

49
Q

What is the main ADR of Aziothioprine?

A

Risk of pancreatitis
Risk of myelosuppression
Requires FBC monitoring (6-8 wks)

50
Q

What is Methotrexate used for?

A

Immunosuppressant used for Chron’s disease

51
Q

What is the main ADR associated with Methotrexate?

A

Interaction w/ NSAIDs leading to toxicity

52
Q

What is the dosing schedule for Methotrexate?

A

Once weekly

53
Q

How should Methotrexate be monitored?

A

FBC
Renal function
LFT
Report fever/cough/dyspnoea

54
Q

What is Ciclosporin?

A

Immunosuppressant used to induce remission in Chronh’s

55
Q

What is the main ADR associated with Ciclosporin?

A

When given w/ steroids increased risk of P. carinii

Prophylactic co-trimoxazole is used

56
Q

What antibiotics should be used when treating IBD?

A

Metronidazole + Ciprofloxacin for 3/12

prophylaxis?

57
Q

What is the main ADR associated with Infliximab?

A

Infusion reactions (20%)

A13THP @ UoN (19 decks)

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