GIT Lec 5 Pt 2 - Irritable Bowel Syndrome Flashcards
What is IBS?
It is a functional disorder characterized by abdominal pain and disordered defection; either diarrhea or constipation or both.
In the absence of detectable structural abnormalities, symptoms include:
1. Increased belching or flatulence
2. Heartburn
3. Nausea and vomiting (non-ulcer dyspepsia)
What are the clinical features of IBS?
IBS is a disease of the outhouse, which occurs almost twice as much in females compared to males.
IBS patients can be categorized in two groups:
1. Patients with abdominal pain associated with diarrhea, constipation or both (most common presentation)
2. Patients presenting with painless diarrhea (less than 20% of cases with IBS)
What are the treatment methods for IBS?
A. Patient counseling and dietary alterations:
Reassurance and careful explanation that IBS is a functional disease that can be prevented by avoiding obvious precipitants like certain foods is helpful in counseling of patients.
The most common precipitants are: coffee, cabbage and legumes.
B. Medications:
1- Stool-bulking agents.
2- Chloride channel activator as lubiprostone.
3- Antispasmodics.
4- Antidiarrhoeal drugs.
5- Antidepressant drugs.
6- Antiflatulence therapy.
7- Serotonin receptor agonist and antagonists.
8- Probiotics.
What are examples of anti-muscaranic drugs?
Scopolamine (hyoscine), atropine, dicyclomine and mebeverine
What is the MOA of anti-muscaranic drugs?
The principle effect of these drugs is to competitively block the binding of acetylcholine to its receptor at:
a- postganglionic cholinergic endings.
b- non-innervated receptors in blood vessels.
c- CNS.
d- some have blocking effect at autonomic ganglia but they don’t block the NMJ (neuromuscular junction) at clinical doses.
What is the MOA of mebeverine (duspitaline)?
It acts directly at the cellular level.
In the gut, it has two actions (components):
1. First, it exerts an anti-spasmodic effect by reducing the sodium ion permeability of smooth muscle cells.
2. Second, it reduces the efflux of potassium ions thereby preventing hypotonia.
What is the pharmacokinetics of Mebeverine?
- It is rapidly and completely absorbed after oral administration.
- It is completely metabolized.
- It is 75% protein-bound
- It’s less effective with chronic use
How do we administer mebeverine?
- It can be taken as needed (p.r.n.) up to 3 times a day for acute attacks.
- It can be taken prior to meals when postprandial pain is to be expected.
What are the side effects of mebeverine?
- Xerostomia
- Headache
- Blurred vision
- Dizziness
- Drowsiness
- Constipation
- Urinary hesitancy and retention
What are the contraindications of mebeverine?
- In children less than 2 years of age
- In patients with paralytic ileus
- In patients with hypersensitivity to it
It should be used cautiously in pregnancy and lactation.
What are examples of anti diarrhea medications, their dosages and their indications?
- Loperamide (2-4mg up to four times dayily)
- Diphenoxylate with atropine (2.5mg Diphenoxylate and 0.025mg atropine)
Both can reduce stools, urgency and fecal soiling.
3.cholestyramine: can be used in patients with cholecystectomy or bile salt malabsorption.
What is an example of anti-depressant drug used in IBS?
Imipramine
What things should be avoided during IBS?
- Chewing gum
- Carbonated beverages
- Artificial sweeteners
- Legumes and foods of the cabbage family
What are examples of anti-flatulence agents?
Simethicone
What are examples of serotonin receptor agonists and antagonists and their use cases?
- Alosetron is A 5-HT3 receptor antagonist, although provides relief in pain and loose motions, .
- Cilansetron, is a newer 5-HT3 receptor antagonist, produces similar beneficial effect.
- The selective serotonin reuptake inhibitor (SSRI), paroxetine has been found to be useful in constipation predominant patients, accelerating orocaecal transit.
4.Mianserin, a serotonin 5-HT2 and HT-3 receptor antagonist with α-adrenoceptor antagonist effects, has record for reducing, pain, distress and functional disabilities.
5.Tegaserod: It is an aminoguanidine indole. It has 5HT-4 partial agonist activity. The effective dose is 6mg twice daily. The serotonin 5-HT4 receptor agonists exhibit prokinetic activity by stimulating peristalsis.
