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Constipation: Types Of Laxatives And How They Work

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Constipation is a gastrointestinal disorder that affects people of all ages, although it is common in women and the elderly. Diet and lifestyle modifications are mostly considered as a first-line of treatment to improve chronic (long-term) constipation. But if it fails to alleviate the symptoms of constipation, laxatives are recommended to manage the condition. Here are common causes of constipation you need to know about!

In this section of Know Your Medicine, we will be explaining about different types of laxatives and how they work.

What are laxatives?

Laxatives are compounds which promote bowel movements and are used to relieve and prevent constipation. Some of these medicines are available over the counter (OTC) and come in the form of capsules, suppositories, enemas, pills, gums, and liquids. Most laxatives are advised to be used only for a short period of time. According to a 2014 study published in the journal Gastroenterology Nursing, around 8% of Indians were reported to have used laxatives to relieve constipation.

Types of laxatives

There are different types of laxatives which are categorized based on their mechanism of action. Some laxatives work on the intestine, some on stools and some on both the intestine and stools. Here is the list of the common types of laxatives:

1. Bulking agents

Bulking agents (such as bran and psyllium) are nothing but fiber supplements, which are usually recommended for normal constipation. Dietary fiber is known to be effective for relieving mild to moderate constipation but not a severe case. People on bulking agents should drink water to maintain hydration. These agents can cause bloating and flatulence.

How does it work: Bulking agents contain fiber which increases the weight of the stools (adds bulk) and improves its consistency by retaining fluid in the stool. This helps the stool to quickly move through the colon (large intestine).

2. Emollient laxatives

Commonly known as stool softeners, emollient laxatives (docusate or mineral oil) act slowly in to help easy elimination of stools. These medicines work best for people who must avoid straining such as those recovering from surgery or those suffering from hemorrhoids (piles).

How does it work: It contains surfactants which increase the water content in the stools. This softens the stools and helps in emptying the bowels. Moreover, it also stimulates the natural contractions of the large intestine.   

3. Osmotic agents

These medicines (milk of magnesia or polyethylene glycol) work on the principle of ‘more the water, softer the stools’. As these laxatives pull excess water from surrounding tissues, it is important to drink more water when taking these medicines to increase efficacy and prevent cramping and gas.

How does it work: Osmotic agents contain poorly absorbable compounds which draw water into the intestine. As compared to other types of laxatives these are known to draw more water, thus softening the stool.

Also read about Common Myths About Constipation.

4. Stimulant laxatives

Stimulant laxatives can act as a medicine to prevent as well as treat constipation. These are usually given to people to empty the intestine before undergoing any diagnostic procedure. It works for a short period of time and may lead to abdominal cramps. It should not be used very often or for long periods as the large intestine might become dependant on the laxative causing the bowel to become lazy.

How does it work: This contains substances which stimulate the intestinal walls, causing it to contract and defecate easily.  

5. Enemas

These are available in bottles as small volume enemas and large volume enemas. Plain water is considered the best fluid for an enema. However, sometimes certain ingredients are added to it. In some cases, it can lead to rectal irritation.

How does it work: Enemas are medicines which help in flushing stool from the rectum and large intestine by causing rectal distention.

Tips for using laxatives:

If you are planning to use a laxative, ensure that you use it only for a short period of time and to treat occasional constipation.

Do not use it regularly.

Stay hydrated when using laxatives.

If you suffer from chronic constipation or if these medicines fail to improve the symptoms, do consult your doctor as constipation can be an underlying symptom of a serious disease like colon cancer.

(The article has been reviewed by Dr. Lalit Kanodia, General Physician)

References:

Rajput M, Saini SK. Prevalence of constipation among the general population: a
community-based survey from India. Gastroenterol Nurs. 2014 Nov-Dec;37(6):425-9.

Portalatin M, Winstead N. Medical management of constipation. Clin Colon Rectal Surg. 2012 Mar;25(1):12-9.

Müller-Lissner S. Classification, pharmacology, and side-effects of common laxatives. Ital J Gastroenterol Hepatol. 1999 Nov;31 Suppl 3:S234-7.

Liu LW. Chronic constipation: current treatment options. Can J Gastroenterol. 2011 Oct;25 Suppl B:22B-28B.

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