GIT Lec 3 Pt 4 - Constipation Flashcards
What is constipation?
Constipation is defined as hard feces that are difficult to expel.
This typically occurs when there’s too much water and electrolyte absorption that occurs in the intestine due to many reasons, like slow intestinal movement; resulting in harder and drier feces that are more difficult to expel.
What are the other names for laxatives?
The term “laxative” has many synonyms like:
1. Purgatives
2. Evacuates
3. Cathartics
4. Aperients
What are the classes of medications that are used in the treatment of constipation?
Constipation medications are classified according to their observed clinical action into:
I. Those that cause watery evacuation within 1-3 hours (osmotics):
A. Saline and osmotic purgatives (magnesium citrate & hydroxide and sodium phosphate)
B. Polyethylene Glycol (PEG) (insoluble alcohol)
C. Lactulose (insoluble sugar)
II. Those that cause soft, semi-solid evacuation within 6-8 hours (irritants and stimulants):
A. Caster oil and diphenolmethane derivatives (Phenolphthalein, bisacodyl and sodium picosulfate)
B. Anthroquinone Derivatives (Senna, Cascara, danthron, rhubarb and aloes)
III. Those that cause evacuation within 1-3 days (bulking agents and emollients (softeners) or surfactant laxatives)
A. Bulking agents (methyl cellulose, psyllium, bran and ispaghula)
B. Emollients (Docusate Sodium, Docusate Calcium, and Docusate Potassium)
IV. Lubricative Laxatives (mineral oil and glycerin suppositories)
V. Prokinetic and other agents (Tegaserod and cisapride)
VI. Chloride-channel agonists (lubiprostone)
What is the general MOA of laxatives?
- By their hydrophilic or osmotic nature, they can cause fluid retention in the intestinal or colonic content, as well as increase their mass.
- They can inhibit fluid and electrolyte absorption by direct or indirect mechanisms
- They can increase the motility of the intestine thereby reducing the time available for absorption of water and electrolytes.
