The basics : Constipation

Today I am gonna give some brief review about how to treat constipation .So let's start with basics

Why constipation occurs ?
-Water serves as a transporter of stools ,decrease in concentration of water in intestine can lead to constipation ,it may be either due to increase absorption from the extracellular space or decrease water content in body.
-Decrease bowel moment

How to treat constipation?
-As now we know cause of the constipation ,we can treat constipation either by :-increasing water content or decrease loss of water from intestinal lumen
And also by increasing bowel moments so less water or salts are absorbed (Yet some drugs uses another mechanism.)

Drugs used :-
1)We can use Dietary fibers which will just form a bulk in intestine and will increase water content of faeces ,also due to bacterial degradation some osmotic active substances are produces which further increases water content Hey but there is one drawback ,it may causes gas :D.
2)Stool softeners:
-They permit water and lipid to penetrate stool .
-They are either given orally or rectally!
(Yes a drug acting on intestine can also given rectally)
-Again there is one drawback ,prolong use can cause impair  absorption of fat soluble vitamins ( A,D,E,K)

3)Osmotic laxatives (Laxative is term used for drugs for treatment of constipation)
-Colon can neither concentrate /dilute fecal fluid  so fecal fluid is isotonic throughout the colon
-Generally we use non-absorable sugars /salts eg:-Magnesium citrate & sodium phosphate.
-Osmotic laxatives are commonly used but should not be used in patient with renal insufficiency.
-But patient using sodium phosphate must take adequate water to compensate fluid loss due to it
,It may causes hyperphosphatemia,hyper natremia , hypocalcemia,hypokalemia.
-So should not be used in cardiac patients

4)Stimulant laxatives
    a) Anthraquinones:It after hydrolysis produces bowel moment in 6-12hrs if given orally or within 2 hrs if given rectally.!
   -It may causes melanosis coli.
   b)Diphenylmethane derivatives : It increases  bowel moments in 6-10hrs when given orally and in 30-60mins when given rectally.
-It has minimum systemic absorption

5) Opioid receptor antagonism
-Now this is  an interesting type of drug mechanism rather than increasing motility it "decreases" motility .

Confused ?!!

Still it is used in prevention of constipation ?!

Yes ,by decreasing motility it prolonges the transient time required for absorption of water and salts from surrounding
Eg:-Methylnaltrexone & alvimopan.

~Ojas