Pathophysiology and Pharmacology6.

Posted: December 26th, 2022

Pathophysiology and Pharmacology6.

Irritable Bowel Syndrome (IBS): Pathophysiology and Treatment
Irritable bowel syndrome (IBS) is a condition affecting the gastrointestinal tract that is hallmarked by repeated abdominal pains and changes in bowel habits. It is more common in women than in men (Huether&McCance, 2017). There is abscence of any overt organic pathological process and the changes in bowel activity alternate between diarrhoea and constipation (Hammer & McPhee, 2014). IBS patients are likely to have psychological symptoms like depression and anxiety. The exact pathophysiology of IBS is not yet well understood. Pathophysiology and Pharmacology6.

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Pathophysiology
The pathophysiologic evidence that is available points at changes in the gastrointestinal tract (GIT) normal flora (microflora). The others are altered immune responses, genetics and disturbances in the brain-GIT axis (Huether&McCance, 2017). The result is changes in motility, visceral sensitivity, and permeability. For those with the IBS of diarrhoea (IBS-D), there are abnormal secretions leading to faster colonic transit and raised intestinal permeability. On the other hand, those with IBS of constipation (IBS-C) have lowered transit times and reduced intestinal motility. These changes are attributed to altered regulation of the brain-gut axis and changes in the neuro-endocrine cells.Other pathophysiologic factors have been found to be food allergies and psychosocial factors like stress and trauma (epigenetic factors). Infectious processes may also play a part. Pathophysiology and Pharmacology6.
Patient Education
The patient education strategies that will be aimed at these patients with IBS will focus on several fronts. Avoiding stimulants will prevent interference with the brain-gut axis. Relaxing and avoiding stress will calm the nerves, while avoiding specific foods will eliminate the allergic trigger. Finally is eating fibre, drinking lots of water, and exercise.
Drug Treatment of IBS
Several medications can be used to manage the symptoms of IBS. Three of these are described below. Their main aim is to relieve abdominal pain and discomfort, and improve bowel function (Katzung, 2018, p. 1,101).
1. Lubiprostone (Amitiza) Pathophysiology and Pharmacology6.
This is a calcium channel activator that is used in IBS with dominant constipation (IBS-C). It acts by stimulating type 2 chloride channel (CIC-2) in the small intestines (Katzung, 2018, p. 1,099). This increases secretion of chloride-rich fluid into the intestines, increasing motility and shortening transit time. Normally it is given 8mcg twice daily. The main side effect to be monitored is nausea.Lubiprostone (Amitiza) interacts with methadone, which appears to reduce its efficacy.
2. Alosetronhydrochloride (Lotronex) Pathophysiology and Pharmacology6.
This drug is used to treat IBS with diarrhoea (IBS-D). It acts by way of being a selective receptor agonist. It undergoes significant first pass metabolism in the liver and is excreted by the kidneys.It is usually given 1mg once or twice daily (Katzung, 2018, p. 1,102). Its side effects include GIT toxicity, constipation, and ischemic colitis. It interacts with the drug fluvoxamine, and should not be given together.
3. Rifaximin(Xifaxan)
This is an antibiotic active against both Gram positive and Gram negative microbes. It acts by inhibiting bacterial protein synthesis. Its side effects include pruritus (itching), dizziness, nausea, and fatigue amongst others.Rifaximin interacts with amiodarone, and concomitant use is not advisable as they affect each other’s efficacy. Pathophysiology and Pharmacology6.