Magnesium Hydroxide (Milk of magnesia 8% suspension). This is a mild purgative which can be used even in pregnant women and children. It absorbs water from the intestines to form the bulk and make the stools soft. Besides purgative action, it counteracts acidity in the stomach.
Dosage: Its usual dose is 15 to 30 ml. Its action starts after 2 to 6 hours.
Adverse Effects: It is a mild purgative without any adverse effect, except to produce flatulence in some people.
Precautions
Take plenty of fluids along with this purgative.
Patients with chronic kidney disease who may have difficulty excreting magnesium, should be wary of Milk of magnesia.
Magnesium Sulfate (Magsulf or Epsom salt)
Magnesium Sulfate is a useful purgative for preparation of bowels before surgery, X-ray examination, colonoscopy and some times to remove dead tapeworms after drugs and poisoning: This is an osmotic purgative which causes total evacuation of the bowel in 1 to 3 hours. Therefore it is given early in the morning in a dose of 5 to 15g.
Lactulose (Duphalac, Livo-Luk)
It is undigestable sugar and retains water. It is useful in constipation and is given in doses of 4 to 109 twice a day. It is broken down in large bowel by resident bacteria into sugar which have osmotic effect. An important use of lactulose is in liver failure. Here it reduces formation and absorption of ammonia which is responsible for causing coma (20 g
twice a day).
Strong Purgatives (Stimulant Purgatives)
They stimulate the musculature of the large bowel and also increase fluid secretion in the bowel. There is passage of semi-solid/liquid stools in 6-8 hours. Often cramping abdomen pain may also occur. Irritant substances such as senna (sennosides), phenolphthalein, bisacodyl (Dulcolox tab and suppositories) and castor oil are included in this class. Because of excess of fluid and ions loss (potassium and sodium) bowel movements ultimately may be reduced (colonic atony). The uterus at full term gets stimulated and therefore they are never used in pregnancy. These are mostly used after deworming treatment, before X-ray examination bowels and before abdominal surgery.
Adverse Effects: The irritation of the intestines may cause griping or cramping pains in the abdomen. Sometimes there may be erosion of the inflamed mucosa passage of mucous in the stools and colonicy atony (inactivity of large bowel). Other adverse effects include an excessive loss of fluids and electrolytes. Phenolphthalein turns stool pink in colour (harmless but patient needs this information). Allergic skin rashes may occur with phenolphthalein, senna an bisacodyl. Colonic mucosa may develop dark pigmentation on regular use of senna.
Precautions
These agents should not be taken regularly for treatment of chronic constipation.
If there is any previous history of abdominal pain, avoid the use of these drugs.
These should never be used by pregnant women as premature uterine contractions may cause abortion.
These are secreted in the milk and should not be used by feeding mothers.
We suggest that purgatives should be avoided as far as possible, especially the strong ones. Most cases of constipation get cured without the aid of drugs. If a purgative must be taken, the the simple, cheap, and effective isapgol is the best option. Cashing on the agony of the constipated individuals, pharmaceutical companies are flooding the market with expensive
preparations containing various combinations of purgatives. In our opinion, no combination is superior to an individual purgative.
Note: Castor oil has been used for many years but its use has gradually declined as more user friendly drugs are now available. In many western countries, specially in Europe, Senna tea is very popular. It does not contain any tea and does not taste like tea. It is a nice a hot decoction whIch also helps move their bowels the next morning.
Purgative Abuse: Some persons take purgatives regularly to keep bowel clean. Habitual use may lead to functional and structural changes in bowel like fluid and electrolyte loss; loss nutrients particularly fat soluble vitamins and proteins; colonic inactivity or spasm; aggravation of disease such as appendicitis and its rupture.
Strong purgatives should not be used in acute abdominal pain and constipation - unless diagnosis is ascertained; if constipation is due to intestinal obstruction; pregnancy; and underfunction of thyroid.
Article Tags: Large Bowel
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