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Drugs for Constipation

Last updated on November 22nd, 2021

Laxative Addiction

The huge sale of cathartics and the large variety of preparations offered for the treatment of constipation are not an index of their value and need, but rather serve to emphasize the misconceptions which exist in relation to colon function. The volume of stool evacuated is governed by the quantity of fibre in the food ingested. The frequency of stool passage is related to the size of the colon, and the state of irritability of the rectum and sigmoid. A daily evacuation may be as normal for one individual as one every two or three days is for another.

An unduly rigid concept of the necessity of daily evacuation is often followed by the habitual use of cathartics, resulting in overstimulation and irritability of the intestine by increasingly potent drugs. Flatulence, abdominal pain, and even heartburn can be the result of the motility disorder thus induced. Thus, for the most part, treatment of functional constipation is the management of a patient with laxative addiction.

Laxative Addiction

Bowel Re-Education

To successfully handle patients with laxative addiction, all laxatives must be stopped and a brief, simple explanation given regarding the physiology of colon function and defecation; emphasis should be placed on the necessity of an adequate fluid intake and the importance of a breakfast sufficient to stimulate peristalsis. Time must be provided so that the individual can go to the bathroom before leaving for business or school in the morning, or at least a regular time for defecation should be established. The patient must understand that it is impossible to establish a normal rhythm of defecation as long as the laxatives and enemas are continued.

The apprehensive patient may be helped initially by the rectal instillation with a bulb syringe of 2 oz. of olive or corn (Mazola) oil at bedtime. This keeps the rectal contents soft and gives the patient something to evacuate in the morning. This procedure is seldom needed after the first few days but may be continued until a regular habit is re-established. The patient must understand that failure to have a bowel movement daily at the outset is not critical; encouragement to persist in the regimen is essential to success. Initially, when bowel irritability is present, phenobarbital gr. ¼ combined with atropine gr. 1/100 to 1/200 three times daily before meals (t.i.d., a.c.) may be of help.

In this stage, also, a diet with a large amount of fibre is not well tolerated and both fruit and vegetables often have to be eliminated until irritability, as judged by pain or flatulence, has subsided. Bland fruits, such as bananas, can then be started, progressing to the addition of more laxative fruits such as prunes. The laxative quality of the food may be increased by the addition of lactose, 2-4 oz. daily.

Physical Aids to Defecation

In addition to this bowel re-education program, other aids to defecation should not be overlooked. These include, especially in the training of children, proper posture with thighs flexed on the abdomen and feet on the floor or adequate support so that good use can be made of the abdominal musculature. Abdominal exercises may be indicated, and when the pelvic floor has been weakened, levator ani exercises should be prescribed.

Physical Aids to Defecation

Special Problem Patients

Bed-ridden patients Bed-ridden patients and those with anal lesions require special consideration. When a patient is confined to bed and has to cope with the discomfort and indignity of a bed pan, constipation leading to impaction must be prevented by the use, when possible, of a bedside commode and by avoiding constipating medications. In many patients, straining is contraindicated and may be avoided by the regular and nightly use of the mildest possible laxative which will achieve the desired result.

In order of preference, milk of magnesia, an anthracene derivative or a hydrophilic colloid may be used. Anal fissure or inflammation of the anus, with or without hemorrhoids, may contribute to constipation through locally induced reflex sphincter spasm. It is most desirable in this instance that the patient have a well-lubricated, soft, single stool daily. Sitz baths and local anesthetic agents may be used along with mineral oil to achieve this objective.

Classification of Cathartics

Agents increasing the intestinal bulk.

Those which increase intestinal bulk by osmotically attracting water into the small intestinal lumen include the saline cathartics. The most drastic of these is magnesium sulfate (45-60 c.c. of saturated solution); less drastic but bad-tasting is sodium sulfate (15 g. in saturated solution). Milk of magnesia (aqueous solution of magnesium oxide) 15-30 c.c. gives a mild laxative action by the same general mechanism. Hypertonic sodium phosphate enemas (Fleet or Travad, 4 fl. oz.) act by a similar mechanism on the rectum and sigmoid and are effective and safe.

In the same general group are the hydrophilic colloids including dried fruits such as figs, apricots and prunes, methyl cellulose in tablet form (sodium carboxymethylcellulose U.S.P., Carmethose 1-2 tablets in water), and a wide variety of agents derived from gums or seeds, such as psyllium hydrophilic mucilloid (Metamucil, 1-2 teaspoonsful in water) and Plantagoovata (Konsyl, 1-2 teaspoonsful in water), Plantagoloeflingii, a vegetable hemicellulose (Mucilose, 1-2 tablets in water), and many other similar preparations.

All of these bulk-producing agents, which should be taken with a large glass of water, act by increasing the volume of intestinal contents, and so encourage normal reflex bowel activity. Their greatest use in functional constipation is when dietary intake is lacking in fibre content, or they may be substituted for bulk-containing food in people with irritable colon syndrome. They are best taken in the morning, since they require in most instances one to three hours to act. These should not be used by patients under treatment with ganglionic-blocking agents, where constipation is best treated by cascara or senna.

Agents lubricating the stool

The only preparation of importance in this category is mineral oil (liquid petrolatum, 15-45 c.c. at night). Flavouring is added in some preparations for increased palatability. Wetting agents or stool softeners, dioctyl sodium sulfosuccinate (Colace or Regulex, 200-240 mg. two to three times daily), soften the stools and appear to allow a better admixture of stool with mineral oil. I have not been greatly impressed with the value of these agents.

Agents producing catharsis by irritation.

— Castor oil, the most potent of this widely used group, affects the small bowel in a matter of a few hours, and should not be used in functional constipation. Compound powder of senna, 10 g., acts in much the same way as castor oil. Senokot (the total active principle of Cassia acutifolia pods), 1-2 teaspoonsful at bedtime, is a milder-acting member of this family. A milder irritant of the anthracene group which stimulates only the colon is aromatic Cascara sagrada fluid extract (1-2 ml. at bedtime). Bisacodyl (Dulcolax, 5-mg. tablets, two to three at bedtime) is a newer colonic irritant preparation of great current popularity. This is also available as a 10-mg. suppository, which exerts its irritant action only on the rectum.


— Tap water at body temperature is the most satisfactory enema when irritation of the colon is to be avoided (500-1500 c.c). Reference has been made to the hypertonic phosphate enemas. Soapsuds enemas produce their action by water stimulation and soap irritation, and are contra-indicated in inflammatory conditions of the colon.

Oil retention enemas of either corn oil (Mazola) or olive oil are useful to soften and lubricate hard fecal masses, and have their greatest value in the relief of fecal impaction and in the management of acutely painful anal lesions.

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