Bowel movements differ from person to person. Whatever the bowel movement pattern is, it’s unique for each person. Having fewer bowel movements (less than three a week) technically is constipation.
The key features that usually define constipation include:
- Dry and hard stools
- A painful bowel movement and stools are difficult to pass.
- Feeling that you have not fully emptied your bowels.
Laxatives: Constipation Remedy
Known by several different names – aperients, purgatives, cathartics; these drugs are used for management and treatment of conditions associated with GIT, wherein the normal motility is greatly reduced. Laxatives aid the patients with fecal retention problems directly by increasing the bulk and smoothening the bowel movement.
Upon long term use, they interfere with the natural bowel movement, causing discomfort.
The distinction of drugs is sometimes made on the intensity of action, as many drugs in low doses act as laxatives and as purgatives at larger doses.
How do Laxatives work?
The laxative drugs primarily aid in increasing the water content in the feces. The action can be achieved by several different mechanisms that form the basis of different types of drugs used for laxative action. The effect is generally achieved by one or more than one of the following mechanisms
- An osmotic action that causes water and electrolytes accumulation, in intestinal lumen. This increases the volume of fecal content and makes it easier to excrete.
- Action on mucosa epithelia, decreasing the overall absorption of water and electrolytes. The intestinal transit is enhanced indirectly by the liquid bulk.
- Cause an increase in the propulsive activity as a primary action that allows less time for absorption of water and salt as a secondary effect.
Laxatives thus modify the fluid dynamic and mucosal epithelia causing fluid accumulation in the lumen by regulating intracellular responses and physiological processes
Laxatives: Different classes of drugs
Bulk-forming laxatives – the laxatives under this class are high-fiber content compounds that absorb water to increase the bulk, hence the name. The formed bulk then distends the bowel movement to initiate reflex bowel activity. These compounds also help in softening the stool for easy passage.
Drugs – psyllium husk, methylcellulose, polycarbophil, bran
Emollient – these laxatives are stool softeners and lubricants. These soften stool by water accumulation in the lumen by action on bolus and increase the penetration of water into the feces. Other than water, they also promote fat into the stools, lubricating both fecal material and intestinal walls.
Drugs – docusate salts (DOSS), liquid paraffin
Hyperosmotic – these are solutes going unabsorbed in the intestine, have a property to retain water osmotically, and distend the bowel; increasing the peristalsis indirectly
Drugs – polyethylene glycol, sorbitol, glycerin, lactulose
Saline – saline laxatives increase the osmotic pressure within the intestinal tract, which results in a higher amount of water to move into the intestinal lumen. The action results in bowel distention, increased peristalsis, and evacuation
Drugs – magnesium sulfate, magnesium hydroxide, magnesium citrate, sodium phosphate
Stimulant – as the name suggests, these agents stimulate the intestinal nervous network. The action on myenteric plexes increases the peristalsis and motility. More importantly, they aid in intestinal water and electrolyte accumulation by modulating the absorptive and secretory activity of mucosal epithelia.
Drugs – castor oil, senna, cascara, bisacodyl
Indications in which they are preferred
- Adjunct in anti-helminthic therapy
- Chronic and acute constipation
- Hepatocellular failure
- Preparation and cleaning bowel before radiography of GIT, proctoscopy, or colonoscopy
- For rapid removal of poisonous substance in the GI tract
- As a post-operative medication to avoid strain
- In bedridden patients
- To avoid strain in patients with a hernia, hemorrhoids, and cardiovascular disease
Common side effects of all laxatives –
- Abdominal cramping
- Fluid and electrolyte imbalance
- Sympathetic reactions – sweating, palpitations, flushing, and fainting
- Cathartic dependence
Specific side effects –
- Bulk Forming Laxatives – Impaction and fluid overload
- Emollient Laxatives – Skin rashes and decreased vitamin
- Hyperosmotic Laxatives – Abdominal bloating and rectal irritations
- Saline Laxatives – Magnesium toxicity (renal insufficient patients), cramping, diarrhea, increased thirst
- Stimulant Laxatives – Nutrient malabsorption, skin rashes, gastric irritation, rectal irritation
- Appendicitis, diverticulitis, ulcerative colitis
- Absence of peristalsis
- A sudden, unexpected change in bowel movement
- Oesophageal obstruction
- Intestinal obstruction
- Fecal impaction
- Undiagnosed abdominal pain
- Colic pain and vomiting
- Drug-induced secondary constipation
- Secondary constipation due to – hypothyroidism, hypercalcemia, malignancies, stricture