Laxative

Products

Laxatives are available in numerous dosage forms. These include, for example, tablets, drops, suppositories, powders, granules, solutions, syrups and enemas.

Structure and properties

Laxatives do not have a uniform chemical structure. However, groups can be identified (see below).

Effects

Laxatives have laxative properties. They stimulate bowel emptying by different mechanisms depending on the active ingredients:

• Stimulation of intestinal movements
• Binding of water in the colon
• Secretion of water and electrolytes into the large intestine.
• Increase the volume of the intestine
• Softening of the contents of the intestine
• Stimulation of the defecation reflex

Indications

Indications for use include:

• Constipation
• Softening of the stool, for example, hemorrhoids or an anal fissure.
• Bowel emptying before diagnostic or surgical procedures.

Agents

Swelling agents swell when absorbed with water, increase stool volume, stimulate intestinal activity and give the intestinal contents a soft texture. They should always be taken with plenty of water:

• Psyllium, Indian psyllium, flaxseed.
• Wheat bran
• Agar, guar
• Tragacanth
• Sterculia gum

Osmotic (saline) laxatives (salts) draw water into the intestine or retain water in the intestine via increased salt concentration:

• Epsom salt (magnesium sulfate), other magnesium salts.
• Glauber’s salt (sodium sulfate)
• Sodium citrate, sodium lauryl sulfoacetate (microclist – enema).
• Laxative salt mixture PH

Sugar alcohols osmotically retain water in the intestine:

• Sorbitol
• Mannitol

Isoosmotic laxatives bind water, make stool softer and more slippery, prevent water and salt loss, and do not irritate the intestines:

• Macrogols: macrogol 4000, macrogol 3350.

Sugars are fermented in the intestine by intestinal flora and lead to an increase in acidity. They stimulate the colon and retain water, resulting in softening of the stool:

• Lactulose (e.g. Duphalac).
• Lactitol (Importal)

Enemas cause stool softening and subsequent bowel evacuation. Glycerol suppositories form a slippery film on the intestinal wall and lead to softening of hardened stool masses by absorbing water from the rectum. This results in stimulation of bowel movements:

• Glycerol (eg Bulboid).

Lubricants soften and lubricate the intestinal contents and lead to an ease of passage in the rectum:

• Kerosene oil, see under kerosene as a laxative.

Stimulant laxatives cause active secretion of electrolytes and water into the intestinal lumen and inhibit reabsorption of electrolytes and water from the colon. Thus, via an increase in volume of the intestinal contents, the filling pressure in the intestine is increased and intestinal peristalsis is stimulated:

• Anthranoids: e.g., senna, aloe, buckthorn, Swedish herbs.
• Fatty oils: e.g. castor oil
• Bisacodyl (Dulcolax, generics)
• Sodium picosulfate (Laxoberon)
• Laxative tea PH
• Phenolphthalein (controversial, out of trade).
• Combination: paraffin-emodel duphalac (PED).

Medical gases:

• Carbon dioxide (lecicarbon, formation from sodium hydrogen carbonate).

Chloride channel activators stimulate the ClC-2 channel, promoting secretion of fluid into the intestine:

• Lubiprostone (Amitiza)

Prokinetics promote intestinal motility:

• Prucalopride (Resolor)

Guanylate cyclase C agonists:

• Linaclotide (Constella)
• Plecanatide (Trulance)

Detergents:

• Docusate sodium