| Three main classes of laxatives are
: 1) Bulk forming agents, 2)Osmotic laxatives, 3) Stool
softeners.
Bulk forming agents--(bran,
psyllium, polycarbophil and methylcellulose)-- Increased bulk
stimulates the natural contractions of the bowel and also
bulkier stools are softer and easier to pass. Bulking agents
act gently and slowly and are among the safest method to
promote regular bowel movements These agents are to be taken
in small amounts at first and the dose is increased slowly
until regularity is achieved. Bulking agents should always be
taken with plenty of fluids.
Osmotic laxatives--appropriate
for short term use. Osmotic agents work by pulling large
amounts of water into the the large intestine making the
stools soft and loose. These laxatives work within 3 hours and
are useful for treating constipation rather than
for preventing it. Usual dose is 15 to 30 ml. once or twice
daily. Some of the osmotic laxatives are listed
below
Milk of magnesia 15-30
mL twice daily
Magnesium citrate
15-30 mL twice daily
Phosphate of soda
15-30 mL twice daily
Lactulose (Chronulac)
15-30 mL twice daily
Sorbitol 15-30 mL
twice daily
Alumina-magnesium
(Maalox, Mylanta)
Polyethylene glycol
(MiraLax) 17 g in 8 oz of water once daily.
Stool softeners
e.g.Docusate sodium (Colace) 100 mg twice daily
Stool softeners increase
the amount of water the stools can hold ,thus increasing the
bulk which in turn stimulates the natural contractions of the
bowel allowing the softened stools to move easily through the
bowels.
Stimulant laxatives
such as senna, cascara, bisacodyl and phenolphthalein are
often used to empty the bowels before diagnostic procedure and
to prevent and treat constipation caused by drugs that slow
the contractions of the large intestines, such as narcotics.
Prolonged use of stimulant laxatives can damage the large
intestine. |