Choice and use of Purgatives

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Chapter: Essential pharmacology : Drugs For Constipation And Diarrhoea

Laxatives are as important for their harmfulness as they are for their value in medicine.


CHOICE AND USE OF PURGATIVES

 

Laxatives are as important for their harmfulness as they are for their value in medicine.

 

All laxatives are contraindicated in:

 

i)     A patient of undiagnosed abdominal pain, colic or vomiting.

ii) Organic (secondary) constipation due to stricture or obstruction in bowel, hypothyroidism, hypercalcaemia, malignancies and certain drugs, e.g.—opiates, sedatives, anticholinergics including antiparkinsonian, antidepressants and antihistaminics, oral iron, clonidine, verapamil and laxative abuse itself.

 

The primary cause should be treated in these cases.

 

Valid Indications of Laxatives Are:

 

1. Functional Constipation

 

Constipation is infrequent production of hard stools requiring straining to pass, or a sense of incomplete evacuation. Constipation is a symptom rather than a disease. Various aspects of the patient’s lifestyle may contribute:

 

·          Misconception about the normal/necessary frequency, amount or consistency of stools.

·          Inadequate fibre in diet, less fluid intake.

·          Lack of exercise, sedentary nature of work.

·          Irregular bowel habits, rushing out for job. Proper assessment of the causative factor in the patient and its correction leaves only a minority of cases to be treated by drugs.

 

Constipation may be spastic or atonic.

 

Spastic Constipation (Irritable Bowel): The stools are hard, rounded, stone like and difficult to pass. The first choice laxative is dietary fibre or any of the bulk forming agents taken over weeks/months. Tegaserod is a new option available now. Stimulant purgatives are contraindicated.

 

Atonic Constipation (Sluggish Bowel): mostly due to advanced age, debility or laxative abuse. Nondrug measures like plenty of fluids, exercise, regular habits and reassurance should be tried. In resistant cases a bulk forming agent should be prescribed. In case of poor compliance or if the patient is not satisfied—bisacodyl or senna may be given once or twice a week for as short a period as possible.

 

2. Bedridden Patients

 

(myocardial infarction, stroke, fractures, postoperative): bowel movement may be sluggish and constipation can be anticipated.

 

To Prevent Constipation: Give bulk forming agents on a regular schedule; docusates, lactulose and liquid paraffin are alternatives.

 

To Treat Constipation: Enema (soapwater/ glycerine) is preferred; bisacodyl or senna may be used.

 

3. To Avoid Straining At Stools

 

(hernia, cardiovascular disease, eye surgery) and in perianal afflictions (piles, fissure, anal surgery) it is essential to keep the faeces soft. One should not hesitate to use adequate dose of a bulk forming agent, lactulose or docusates.

 

4. Preparation Of Bowel For Surgery, Colonoscopy, Abdominal X-ray

 

The bowel needs to be emptied of the contents including gas. Saline purgative, bisacodyl or senna may be used; castor oil only in exceptional circumstances.

 

5. After Certain Anthelmintics (especially for tapeworm)

 

Saline purgative or senna may be used to flush out the worm and the anthelmintic drug.

 

Fixed dose combinations of an anthelmintic (other than piperazine) with a purgative is banned in India, as are laxatives with enzyme preparations.

from the intestines. Only saline purgatives are satisfactory.

 

The choice of a purgative depends on the latency of action and type of stools desired. This is given in Table 48.1.

 


 

Some Combined Preparations

 

AGAROL: Liquid paraffin 9.5 ml, phenolphthalein 400 mg, agar 60 mg per 30 ml emulsion.

 

CREMAFFIN: Milk of magnesia 11.25 ml, liq. paraffin 3.75 ml per 15 ml emulsion; CREMAFFIN PINK with phenolphthalein 50 mg per 15 ml.

 

JULAX: Bisacodyl 10 mg, casanthranol 10 mg dragees. PURSENNIDIN (with DOS): Purified senna ext. (cal salt) 18 mg, docusates 50 mg tab.

 

Purgative Abuse 


Some individuals are obsessed with using purgatives regularly. This may be the reflection of a psychological problem. Others use a purgative casually, obtain thorough bowel evacuation, and by the time the colon fills up for a proper motion (2–3 days) they get convinced that they are constipated and start taking the drug regularly. Chronic use of purgatives must be discouraged. Once the purgative habit forms, it is difficult to break. Dangers of purgative abuse are:

 

1.       Flairing of intestinal pathology, rupture of inflamed appendix.

2.       Fluid and electrolyte imbalance, especially hypokalaemia.

3.       Steatorrhoea, malabsorption syndrome.

4.       Protein losing enteropathy.

5.       Spastic colitis.

 

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