Keele Constipation

Front 1

What are the functions of the large intestine?

Back 1

-Reabsorb water and compact material into faeces

-Absorb vitamins produced by bacteria

-Store faecal matter prior to defecation

Front 2

What are the different sections of the colon?

Back 2

-Ascending

-Transverse

-Descending

-Sigmoid

-Rectum

-Anal Canal

Front 3

What happens in the proximal half of the colon?

Back 3

Absorption

Front 4

What happens in the distal half of the colon?

Back 4

Storage

Front 5

What is the transit time through the large intestine?

Back 5

36-48 hours

Front 6

What are mixing movements known as?

Back 6

Haustrations

Front 7

What are propulsive movements known as?

Back 7

Mass Movements

Front 8

List the symptoms of constipation (at least two have to be present for more than 3 out of 6 of the past months)

Back 8

-Straining of the stool at least 25% of the time

-Hard stools at least 25% of the time

-A feeling of incomplete evacuation at least 25% of the time

-A feeling of anal blockage at least 25% of the time

-Manual maneuvers for rectal emptying at least 25% of the time

-Two stools or less per week

Front 9

What are the intrinsic factors causing constipation?

Back 9

-Abnormal intrinsic motility

-Lack of luminal factors (stretching, chemical and tactile stimuli)

-Lack of extrinsic innervation (in paraplegia)

-Hormones

Front 10

What factors cause constipation?

Back 10

-Intrinsic Factors

-Medications

-Impaired defecation

-Fluid handling & faecal impaction

Front 11

What is Iatrogenic Constipation?

Back 11

Constipation caused by medication

Front 12

What types of medicines can cause constipation?

Back 12

-Pain medications

-Iron

-Calcium

-Blood pressure medication

-Opiods

Front 13

How do Opioids cause constipation?

Back 13

Increase smooth muscle tone:

-Suppresses forward peristalsis

-Increases tone in anal sphincters

-Increases transit time and water absorption

Reduces sensitivity to anal distention

-Reduces urge to defecate

Front 14

What happens during laxative misuse?

Back 14

-Longer interval needed to refill colon> misinterpreted as constipation>further laxative use

Enteral loss of water and salts causes release of aldosterone:

-stimulates reabsorption in intestine, but increases renal excretion of K+

-double loss of K+ causes hypokalemia, causing reduced peristalsis

-Misinterpreted as constipation

-Further laxative use

Front 15

The Defecation Reflex

Back 15

Front 16

What are the three stages of defecation?

Back 16

1) Holding- Puborectalis external and internal anal sphincters contracted

2) Initiation- Puborectalis and external anal sphincter relax. Levator ani, abdominals and diaphragm contract

3) Completion- Internal and external anal sphincters relax. Rectum contracts

Front 17

What leads to impaired defecation?

Back 17

Loss of feedback between holding, initiation and completion.

Front 18

Faceal Impaction

Back 18

Front 19

What are treatments of constipation?

Back 19

-Dietry Modification

-Medication

Front 20

What are the different therapy classes for constipation?

Back 20

-Bulk-forming laxatives

-Osmotic laxatives

-Stimulant laxatives

-Stool softeners

-Other agents

Front 21

Mechanisms of Action of laxatives

Back 21

Front 22

What are the contraindications to using laxatives?

Back 22

-Undiagnosed abdominal pain

-inflamed organs-> could cause GI contents to spill into abdominal cavity-> peritonitis (life-threatening)

-Some drugs contraindicated when a GI disturbance is likely to be worsened by increased motility (intestinal obstruction, faecal impaction or inflammatory bowel diseases)

Front 23

What do bulk laxatives do?

Back 23

-Cause an increase in bowel content volume, which triggers stretch receptors in the intestinal wall

-Causes reflex contraction that propels the bowel content forward

Front 24

How long can it take for the effect of bulk laxatives to take place?

Back 24

-Several days to around 2 weeks

Front 25

What are the physical properties of bulk laxatives?

Back 25

Insoluble, non-digestible and non-absorbable

Front 26

What are some examples of bulk laxatives?

Back 26

-Isphagula

-Methylcellulose

-Sterculia

Front 27

What are the adverse reactions of bulk laxatives?

Back 27

-Bloating and flatulence, GI obstruction and impaction

Front 28

What are the contraindications of bulk laxatives?

Back 28

-Colonic atony (colon won't be stimulated by activation of strech receptors

-Facecal impaction & intestinal obstruction (increased motility won't lead to defecation)

Front 29

How long does it take for the effects of osmotic laxatives to occur?

Back 29

1-3 hours

Front 30

What are osmotic laxatives used for?

Back 30

To purge intestine (prior to surgery or poisoning)

Front 31

How do osmotic laxatives work?

Back 31

Fluid is drawn into or retained in the bowel by osmotic force> increases volume> triggers peristalsis

Front 32

What are the two classes of osmotic laxatives?

Back 32

-Nondigestible sugars and alcohols

-Salts

Front 33

What are some examples of nondigestible sugars and alcohols?

Back 33

-Lactulose (broken down by bacteria to acetic and lactic acid> causes osmotic effect)

-Macrogol 3350- polymer of ethylene glycol

Front 34

What are some examples of salts used as laxatives?

Back 34

-Magnesium hydroxide

-Sodium phosphates (enemas)

-Epsom salts (MgSO4)

Front 35

What are the two main issues of osmotic laxatives?

Back 35

-Increased GI activity

-Electrolye & Osmotic imbalances

Front 36

What are the ADRs of osmotic laxatives?

Back 36

Abdominal discomfort, diarrhoea

Front 37

What are the cautions of osmotic laxatives?

Back 37

-Broadly those at danger of dehydration and those at risk of electrolyte imbalance

Front 38

What are the contraindications of osmotic laxatives?

Back 38

-Acute GI conditions

-Intestinal obstruction and inflammation

Front 39

What are stimulant laxatives indicated for?

Back 39

Severe constipation where more rapid effect is required (6-8 hours)

Front 40

How do stimulant laxatives work?

Back 40

Irritate GI mucose and increase intestinal motility

Front 41

What are some examples of stimulant laxatives?

Back 41

-Bisacodyl

-Anthraquinones: Co-danthramer, Co-danthrusate, Senna

-Cascara, Castor oil

Front 42

Pharmacology of Stimulant Laxatives

Back 42

Front 43

Which laxatives show evidence of carcinogenicity and genotoxicity?

Back 43

Co-danthrusate and Co-danthramer (used limited to patients with terminal illnesses)

Front 44

What are some examples of stool softeners/emollients?

Back 44

-Docusate sodium (surfactant and stimulant)

-Arachis oil (enema- contains peanut oil)

-Liquid paraffin (oral solution, extemporanoues preparation)

Front 45

What is the oral dose of docusate sodium?

Back 45

Up to 500mg daily, divided doses

(acts within 1-2 days)

Front 46

What is the rectal dose for docusate sodium?

Back 46

120mg for 1 dose (acts within 20 minutes)

Front 47

What are the ADRs of docusate sodium?

Back 47

Abdominal pain, diarrhoea, hypokalaemia

Front 48

What are the cautions of docusate sodium?

Back 48

Patients where hypokalaemia tobe avoided; Rectal preparation notindicated with haemorrhoids

Front 49

What are the contraindications of docusate sodium?

Back 49

Intestinal blockage

Front 50

Opioid Antagonists for Opioid-Inducedconstipation

Back 50

Front 51

What is Methylnaltrexone?

Back 51

Peripherally acting opioid antagonist

Front 52

How is Methylnaltrexone administered, and what dose is given?

Back 52

Subcutaneous injection; 8-12 mg 4-7doses/week

Front 53

What are the ADRs of Methylnaltrexone?

Back 53

Abdominal pain, diarrhoea;flatulence

Front 54

What are the cautions and contraindications of Methylnaltrexone?

Back 54

-Cautions: Patients with damaged GI tract-Contraindications: Acute surgicalabdominal conditions; Intestinal blockage

Front 55

What three opioid antagonists are used for opioid-induced constipation?

Back 55

Methylnaltrexone, Prucalopride and Lubiprostone (Amitiza)

Front 56

What is Prucalopride, and what dose do you give?

Back 56

• Selective 5HT-4 agonist with prokineticproperties• 2mg once daily, review after 4 weeks

Front 57

What are the ADRs, Cautions and Contraindications of Prucalopride?

Back 57

• ADRs - wide range of abdominal side effects associated with action• Cautions – arrythmias & ischaemic heart disease (hERG)• Contraindications – Crohn’s disease, abdominal obstruction and other serious GI conditions

Front 58

What is Lubiprostone (Amitiza), and what dose do you give?

Back 58

• Chloride channel blocker – acts locally toincrease fluid secretion and motility• 24 µg (micrograms) twice daily for 2-4weeks

(Has low oral bioavailability-actions in GI tract)

Front 59

What are the ADRs and CIs of Lubiprostone?

Back 59

-ADR’s – wide range of abdominal sideeffects associated with action-Contraindications – GI obstruction