GI Pharmacology Flashcards
Why do patients get constipate? The mechanism behind constipation
Decreased peristalsis which could be a result of medication or age etc
Give an example of medication which can contribute to constipation?
Opioids
What is senescence?
the condition or process of deterioration/downregulate with age
Why are older people more likely to have constipation?
process of senescence
What are the 2 forms of laxatives?
Bulk laxatives
irritant laxatives
What are the 2 types of bulk laxatives?
hydrophillic gels
osmotically active laxatives
alcohol and dissacharide based laxatives
Where in the GI tract are faeces found?
colon and rectum
What’s the name of the dehydratable slime in the small intestine?
chyme
What are the characteristic of bulk forming laxatives?
Insoluble
non-absorbable, cannot permeate through epithelial gut lining
Describe how bulk forming laxatives work
contains large macromolecules which increases coloidal pressure in the intestine thus drawing more water into intestine.
Form larger, softer stool which activate stretch receptors in the bowel, causing it to contract and relax moving bolus of faeces forward.
Before administering bulk laxatives to a patient, what must you ensure about the patient’s condition?
That they are thoroughly hydrated otherwise, insufficient amount of water will be drawn into the stool
List examples of hydrophilic gell bulk forming laxatives
Bran
Ispaghula Husk
Methyl cellulose
Sterculia
What is the name of the nerve fiber network which is solely found in the GI tract and controls it’s motility?
Myenteric Plexus
How many muscle layes are in the GI tract and what are they called
2 muscle layers,
Circular and Longitudinal
Where is the Myenteric plexus found?
In the GI tract, sandwhiched between the circular and longitudinal muscle layers.
What is the Myenteric plexus?
nerve fiber network which is solely found in the GI tract and controls it’s motility
What does the efficacy of bulk laxatives (hydrophillic gel) laxatives depend on?
Patient being hydrated
What are osmotically active
bulk forming laxatives?
Made up of epsom salts or glauber salts which increase osmotic pressure in the bowels.
What are the contraindications for epsom salts for laxative use?
Renal Failiure
What are the contraindications for Glauber salts?
Hypertension
Heart Failiure
Oedema
What is the name of the dissacharride found in Macrogol?
polyethylene glycol
Why does macrogol contain electrolytes aswell?
Reduces possibility of electrolyte imbalance and dehydration
What is addes to macragol to help reduce possibility of electrolyte imbalance and dehydration?
electrolytes
Why is Lactulose a useful laxative for those wth hepatic failiure?
Acidifies intestine and destroys gut flora to stop production of ammonia gas and ammonium ions.
Which laxative should be indicated for someone with hepatic failiure?
Lactulose
What is the mechanism of stimulant laxatives?
Irritates mucosal layer of GI tract causing reabsorbtion of electrolytes resulting in some fluid to enter.
Irritation of mucosal layer also triggers irritation of muscle layer which cause the muscles to contract
Why should you not give someone with a bowel obstruction laxative? especilly stimulant laxatives?
Forfully contracting the bowels on an obstruction can potentially cause a rupture
What are the potential cause for decreased peristalsis?
medication -opiods
spinal injury
bowel obstruction
What are the two elements for controlling the passing faeces?
autonomic and somatic control
How long does it normally take for an empty colon to fill?
24-48 hours
How does a patient develop laxative dependence?
Patient takes laxative without allowing time for faeces to move down colon. results in expulsion of material from ascending and transverse colon.
Patient loses water and electrolytes because of this which dehydrates patient.
Retention of sodium due to dehydration results in loss of potassium.
Low potassium (hypokalaemia) means reduces peristalsis since potassium is integral for the contraction of muscle.
This in turn means that the patient will need to take more laxatives
Which laxative is less likely to result in laxative dependence?
movicol
How do we prevent the occurence of laxative dependence on patients?
Educate patients on the use of laxatives:
explain it will trake longer for the patient to defecate afterwards.
Ensure that the patient is thoroughly hydrated
awareness that it may take a while to get
What are the indication for laxative use?
Preperation for surgery/bowel pathology (bowel prep)
constipation
Which groups need to be give special consideration before administering laxatives?
Older people
young children
According to Paediatric guidelines, what should be the first line laxative given to a paeds patient?
polyethylene glycol 3350 (movicol) +elecetrolytes.
May be mixed in with a cold drink
What should be administered to a paeds pateient if after giving a first line laxative disimpaction does not occur?
A stimulant laxative
when should a stimulant laxative be administered to a paeds patient if first line laxative does not work?
2 weeks if disimpaction does not occur
What is the nurse role in terms of caring for a p[atient taking laxatives?
Assessing their need for laxatives
Monitoring the patient whilst they are on laxative medication
Evaluate the patients cureent situation to develop care
Which cells in the stomach secrete gastric acid?
The parietal cells in the inner lining of the stomach
What substances are secreted by parietal cells?
HCL (gastric acid) and intrinsic factors
What is the purpose of gastric acid interms of digestion?
activates enzymes required for digestion
What is another term (scientific) for indigestion?
dyspepsia
List the types of acid reducing medications you need to know for the exam
Antacids
H-2-receptor anatagonists - HR2 As
Proton pump inhibitors-PPIs
What are the consequences of giving acid reducing medication?
affects homeostasis of the digestive system
Which part of the GI tract is acidic fat-soluble likely to absorbed and why?
The stomach because it is an acidic environment
How do Antacids work?
They are basic and help neutralise the acid in the stomach.
