GI tract Flashcards
Bulk forming Laxatives
(hydrophillic gels)
Insoluble
Non-absorbable
- Bran
- Ispaghula Husk
- Methyl Cellulose
- Sterculia
Osmotic laxatives
Affect stretch receptors
Epsom salts
MgSO4
Glauber’s Salts NaSO4
However Epsom Salts:
Contraindicated in renal failure
Glauber’s salts:
Contraindicated in hypertension
Alcohol and disaccharide laxatives
Sorbital, manitol:
Can’t permeate the intestinal wall
Macrogol (movicol)
Polyethylene glycol + electrolytes help reduce the possibility of electrolyte imbalance and dehydration
Lactulose
Acidifies the intestine and destroy gut flora, useful in hepatic failure to stop the production of Amonia and ammonium
Common Stimulant laxatives
Bisacodyl
Danthron
Docusate Sodium
Glycerol
Senna
Sodium Picosulphate
Mechanisms of Stimulant
Direct Stimulation of Intestinal Smooth Muscle:
* Stimulant laxatives activate nerve endings in the intestinal wall (enteric nerves), leading to increased peristalsis (contractions of the intestinal muscles). This propels stool through the colon more rapidly.
* Enhanced peristalsis reduces the time available for water absorption from the stool, keeping it softer and easier to pass.
Electrolyte and Fluid Secretion
* Stimulant laxatives promote the secretion of water and electrolytes (e.g., sodium, chloride) into the intestinal lumen.
* They inhibit the absorption of water and electrolytes by the intestinal cells, increasing the fluid content of the stool.
Laxative defecation
Normal defecation–> descending colon emptied
With laxative defecation the whole colon is emptied
The empty colon will take 24-48 hours to fil, so patient thinks they are constipated again so take more laxtives which leads to expulsion of material from the ascending and traverse colon
Problems with Laxative dependence
Loss of semi fluid material from the ascending colon
Loss of constituent fluid causes dehydration
Kidneys secretes Aldosterone which retains Na+ at the expense of losing K+
Loss of K+ leads to hypokalemia which in turn leads to a loss of peristalsis Which causes constipation
indications for use of laxatives
Preparation for Surgery / Radiological Procedures
Bowel pathology
Constipation
-Natural
-Drug induced
Nursing considerations
Determine a patient’s regular bowel habit
what is normal for them
Is the patient constipated?
Nurse’s role
Assess
Monitor
Evaluate
Separate laxative (bulk forming)administration from other medications (minimum 30 ideally 1 hour)
Don’t prescribe laxatives if there is suspected:
Intestinal obstruction or perforation.
Paralytic ileus.
Colonic atony or faecal impaction (bulk-forming laxatives).
Crohn’s disease or ulcerative colitis.
Toxic megacolon.
Severe dehydration (bisacodyl).
Galactosaemia (lactulose).
History of hypersensitivity to peanuts (arachis oil enema).
Prescribe laxatives with caution if there is:
Fluid and electrolyte disturbance —discontinue treatment if there are symptoms of fluid and electrolyte disturbance.
A history of prolonged use — due to the risk of electrolyte imbalance, such as hypokalaemia.
Cardiovascular disease — do not prescribe more than two sachets of full-strength macrogol compound oral powder in any one hour, and advise the person to discontinue if symptoms of fluid and electrolyte disturbance occur.
Lactose intolerance (lactulose) — may cause diarrhoea.
Ischaemic heart disease or arrhythmias (prucalopride).
Ischaemic colitis (macrogel).
Movicol is considered high in sodium, this should be taken into account for those people on a low salt diet.
choice of laxatives in children
The choice of laxative will depend on the age of the child, the formulation preferred (liquid or tablet), and individual preference.
osmotic laxatives
Polyethylene glycol 3350 plus electrolytes (macrogol) — Movicol® Paediatric Plain is the only macrogol licensed for use in children. It is unflavoured, but fruit squash may be added if preferred.
Each sachet should be dissolved in 62.5 mL (quarter of a glass) of water.
Movicol® is also available in a sachet containing a ready to take oral solution for children aged 12 years and above.
Lactulose — this is a very sweet liquid, and it may be given with water.
stimulant laxatives for children
Senna — many children find the liquid formulation unpalatable; however, the tablets can be taken from 2 years of age (off-label use below 6 years of age) if preferred.
Docusate — has a relatively weak stimulant effect, but also stool-softening properties. It is available as both a liquid formulation and capsules. Only the liquid formulation is licensed for use in children younger than 12 years of age.
Bisacodyl — tablets are licensed for use in children aged 12 years and older.
Sodium picosulfate — the liquid formulation is very sweet; the capsules are licensed for use in children aged 4 years and older.
antacids
class of medications used to neutralize stomach acid, providing symptomatic relief for conditions like heartburn, acid indigestion, and gastritis. They act quickly but provide short-term relief.
Mechanism of Action
of antacids
Neutralization of Gastric Acid:
Antacids are weak bases that react with hydrochloric acid (HCl) in the stomach to form water and a neutral salt. This increases the pH of the stomach contents, reducing acidity.
The chemical reactions vary depending on the active ingredient
