Constipation (and also hemorrhoids) is an embarrassing condition that no one likes to discuss.

The truth is constipation is something many people in the Western world suffer from on a chronic (long-term) basis.

Both chronic and acute (abrupt onset) constipation can be a significant source of discomfort. Moreover, the extra straining to pass stool can cause hemorrhoids, or make pre-existing hemorrhoids worse, so constipation is something to avoid if at all possible.

Laxatives are frequently used to treat constipation yet most people don’t know exactly what they are, how they work or that the long-term abuse of self-administered stimulant laxatives can have long-term effects on the way your bowel works.

This article is going to give a description of how laxatives work. It is also going to discuss the worrisome side effects of stimulant laxatives, and the dangers of laxative abuse.

Finally, it will suggest safe ways to take stimulant laxatives on a long-term basis.


Why Do We Become Constipated?

In order to understand how laxatives work, it’s important to know why we become constipated in the first place.

One of the reasons we become constipated is because there’s not enough gut motor activity to propel the stool toward the rectum and completely evacuate the bowels.

Stool is formed in the colon, which is at the lower end of the gastrointestinal tract. By the time digested food reaches the colon, most of the nutrients have been absorbed.

It’s your colon’s job to remove fluid from the intestinal contents and expel the waste.

Your colon does this by absorbing fluid and using muscular peristaltic contractions to push the stool to the rectum which acts as a temporary storage facility for the unneeded material. As the rectal walls expand, a nervous signal is generated, stimulating the desire to defecate.

Normally, waste products are excreted within 35 – 70 hours, resulting in a normal bowel movement 3-12 times per week. However, if there’s a slowing of peristalsis then the colon has more time to soak up water from the stool and it can become hard and dry so it’s difficult to expel.

Equally, if there’s anything affecting the muscles, then it doesn’t matter how many nerve impulses arrive, not much will happen. That’s a form of constipation.


How is Constipation Treated?

There are a number of different approaches to treating constipation including lifestyle measures and laxatives.

Lifestyle measures as a treatment for constipation

Potentially beneficial lifestyle changes for temporary constipation include increasing intake of dietary fiber, increasing fluid intake, and enhancing physical activity.

Slowly increasing the amount of fiber in the diet to 20-25 g per day may improve bowel function by adding bulk and softening the stool.

There aren’t any data from placebo-controlled studies that support the use of hydration, or even exercise as primary therapies forchronic constipation. Nevertheless, some people may benefit from these easy first line types of therapies. And, there are other benefits that could accrue from things such as increasing exercise.

Laxatives as a treatment for constipation

If lifestyle measures are not effective, you should try laxatives.

Basically, there are four types of laxatives as summarized in Table 1: Bulking agents, osmotic laxatives, stimulant laxatives, and stool softeners.i

Table 1. Laxatives Commonly Used for Constipation
Type of Laxative Maximal Recommended Dose

How It Works

How Long It Takes
Bulking Agent
Bran fiber

Psyllium (Metamucil)

Methylcellulose (Citrucel)

Polycarbophil (Fibercon)

Titrate up to 20 g

Absorbs water to form soft, bulky stool

12-72 h
Osmotic Laxative
Saline laxative:

Magnesium hydroxide

Sodium phosphate

Poorly absorbed sugar:

Lactulose, sorbitol, mannitol, lactitol, glycerin suppositories

Polyethylene glycol 3350 (Miralax)


15-30 ml once or twice daily

10-25 ml with 12 oz of water as needed

15-30 ml once or twice a day

17-36 g once or twice a day

Draws water into the colon from surrounding tissues prompting normal contraction of intestinal muscles

1 h-several days



.30 min- 3 h

Stimulant Laxative
Diphenylmethane derivatives:

Bisacodyl (Dulcolax, Correctol)

Sodium picosulfate (Lubrilax, Sur-lax)


Senna (Senokot, Ex-Lax)

Cascara sagrada (Colamin, Sagrada-lax)

Castor oil (Purge, Neoloid, Emulsoil)

5-10 mg every night

5-15 mg every night

187 mg daily (equivalent to 20-30 mg sennoside B)

300 mg (or 5 ml) daily (equivalent to 20-30 mg cascaroside A)

15-30 ml daily

Triggers peristalsis in addition to water and electrolyte secretion to eliminate stool

6- 24 h
Stool Softener
Ducosate 100 mg twice a day

Works by making your stools more permeable to fat and water making them softer and easier to pass.

12 h- 5 days


Bulking agents, mainly fiber, but also other polymers, accomplish their action by increasing the volume of the stool, and will both soften the stool and increase colonic activity. This stimulates the bowel to pass the stool in a normal manner; gas and bloating are common side effects. Bulking agents may work as quickly as 12 hours after use or take as long as 3 days to be effective.

Osmotic laxatives pull water into the bowel from surrounding tissues which increases the size and pliability of the stool. When ingested on an empty stomach, they may take only 1 to 2 hours to take effect. Dehydration can occur when osmotic laxatives are overused.

Stimulant laxatives increase colonic motility and secretion by stimulating the colonic nerves. They work within 6 hours when administered orally and within 30 minutes to 2 hours when given intrarectally. Stimulant laxatives may cause abdominal cramps.

Stool softeners soften stool by allowing water to interact more effectively with solid stool. Ducosate is also thought to exert a stimulant laxative effect. A laxative effect usually occurs within 1 to 3 days of administration. But your body can quickly get tolerant of these, so they’re unlikely to be much use for a chronic situation.


What Are the Major Stimulant Laxatives?

The major stimulant laxatives are diphenylmethane derivatives and anthraquinones.

Diphenylmethane stimulant laxatives (e.g., bisacodyl) have a profound effect on colonic stimulation and are unique in that dosing titration is based on an individual’s response versus a conventional dosing range.

Anthraquinone stimulant laxatives are naturally occurring herbal products (glycosides) found in extracts of senna leaf and pod (a Middle Eastern laxative), aloe (known worldwide), cascara sagrada (a North American laxative), buckthorn (also known as frangula; a European laxative), and rhubarb root (the prominent Chinese laxative).

Anthroquinone glycosides are converted by colonic bacteria to their active form. These molecules promote water retention in the stool and stimulate increased peristalsis. Onset of action is 6 hours, which is the time required for transport of the laxative to the colon. With rectal stimulation, the time to evacuation is within 30 minutes to 2 hours.

As summarized in the Table below, anthoquinone laxatives include senna, aloe, cascara sagrada, buckthorn, and rhubarb root.


Herbal Stimulant Laxatives Plant Active Ingredient Intermediates
Senna Cassia angustifolia

Cassia acutifolia

Sennoside A+B Rhein
Aloe Aloe ferox

Aloe barbadensis

Aloines A+B Aloe-emodin
Cascara sagrada Rhamnus purshiana Cascaroside A+B Aloe-emodin
Buckthorn (frangula) Rhamnus frangula Franguline A+B Emodin
Rhubarb root Rheum palmatum Sennoside A+B Rhein, emodin

Note: To clear up any confusion, the active ingredients in the table above are all types of Anthroquinones. For example 20mg of sennoside B is also the same as saying 20mg of anthroquinones. It is important to understand this, to understand fully the discussion below.

Senna. The dried leaflets and pods of Cassia senna is most often referred to as senna. These preparations contain the strong glycosides sennoside A and B. The typical dose is 187 mg (equivalent to 20-30 mg of sennoside B). Similar activities are found in Rhubarb root preparations, although rhubarb is more commonly used in Asia.

Cascara sagrada. Considered “sacred” bark by those using it, cascara sagrada comes in a variety of forms, in tablets, capsules, and liquid extracts. It is cascaroside A+B which give cascara sagrada its laxative action. A typical dosage of cascara sagrada is 300 mg capsule (corresponding to 20-30 mg cascaroside A) taken in the early evening to stimulate a bowel movement in the morning.

Aloe. Alois powder is the solid residue obtained by evaporating the liquid which drains from the cut leaves of Aloe ferox. It is the aloin that is converted into emodin-derivatives within the colon that is responsible for its laxative effect. The optimum dose is the smallest dosage necessary to obtain a soft stool; for many this is one 250 mg capsule while others may need 450 mg or more to obtain this effect.

Anthroquinones are also present in vegetables such as cabbage and lettuce, being particularly high in beans (36 mg/kg fresh weight). Needless to say, these vegetables are very effective in helping overcome constipation.

Herbal stimulant laxatives are frequently used to treat constipation because they are assumed safe. However, you should understand that herbal products are not reviewed or approved by the US Food and Drug Administration, and that many questions regarding their efficacy and safety profiles remain unanswered. The use of herbal stimulants should be considered only after lifestyle, and bulk laxatives have proven ineffective.

They are contraindicated in cases of bowel obstruction, acute intestinal inflammation and abdominal pain of unknown origin. They should not be used in children under 12 or in pregnant or nursing mothers.


What Are the Side-Effects of Stimulant Laxatives?

The side-effects of stimulant laxatives are:

  • Diarrhea
  • Loose stools
  • Vomiting
  • Abdominal cramps
  • Bloating
  • Rectal irritation

Cascara sagrada and senna commonly cause yellow-brown urine; this is harmless.

Stimulant laxatives work by increasing rhythmic muscle contractions (peristalsis) in the colon. Thus, they may induce abdominal discomfort and even cramping abdominal pain, ii as you might expect.

There are other side-effects of stimulant laxatives. If you have any of the following symptoms, stop taking them and call your doctor immediately:

  • Bloody stools
  • Severe cramping
  • Pain
  • Weakness
  • Dizziness
  • Unusual tiredness
  • Rectal bleeding
  • Unrelieved constipation

Overuse and abuse of stimulant laxatives can cause diarrhea and potassium deficiency, which can lead to muscle weakness and heart function disorders.


Safety Issues Affecting Stimulant Laxatives

Are stimulant laxatives dangerous?

Yes. Although anthraquinone stimulant laxatives are generally considered harmless because of their natural origin, several health problems may arise from their prolonged use, including electrolyte imbalance, particularly potassium deficiency, cathartic colon,iii melanosis coli,iv and increased risk of colorectal cancer.v

Let’s look at the concerns regarding the safety of aloe as an example.

Safety of aloe a concern

Aloe, a popular houseplant, has a long history as a multipurpose folk remedy. Because aloe is well-known as a gently external treatment for minor burns and skin irritations, it’s easy to assume that it would be safe for use internally as well. But this is not necessarily true. Even though aloe vera is a plant, it contains anthroquinones (aloines A+B, aloe-emodin) which produce a laxative effect by increasing colonic peristalsis and intestinal water content. In plain English, this means that aloe causes faster and stronger contractions of the colon which may produce violent abdominal cramps, painful spasms, and diarrhea, especially at higher doses.

All anthroquinone-containing stimulant laxatives (not just aloe, but senna and cascara sagrada as well) can cause melanosis coli, cathartic colon, and possibly increase the risk of colorectal cancer. In fact, genotoxicity studies show that aloe-containing laxatives pose cancer risks to humans even when used as directed!

And if this isn’t bad enough, chronic use of aloe can also lead to serious medical consequences such as potassium deficiency, which can lead to muscle weakness and heart function disorders, steatorrhea, gastroenteropathy, osteomalacia, and vitamin and mineral deficiencies. In addition, aloe may interact negatively with a number of pharmaceuticals, including thiazide diuretics. Even after discontinuing the use of laxatives, changes in the colon may only partially return to normal because of permanent drug-induced nerve damage to the colon.

What’s really scary about aloe is that it’s a very common ingredient in all sorts of liquid vitamin, energy boost drinks, and these product labels won’t note that aloe is a laxative.

Aloe is even specifically marketed to people with Irritable Bowel Syndrome or chronic constipation as a “digestive aid”, “soothing to the bowel”, with an emphasis on the fact that it’s an all-natural plant ingredient, which again just hides the fact that it is without doubt a harsh stimulant laxative.

It’s possible to find aloe from which the anthraquinones have been removed. If this is the case, the label should specifically say so, or something to the effect that “diarrhea-causing ingredients”, “aloin and aloe emodin” have been removed from the product.


What Is Cathartic Colon?

Cathartic colon is a historic term for the anatomic alteration of the colon secondary to chronic stimulant laxative use.

Physicians generally warn against the use of stimulant laxatives due to concern the colon resulting in a “sluggish” colon.

Studies have shown that chronic (>3 times/week for 1 year or longer) use of anthraquinone glycosides is associated with destruction of nerves within the colon, suggesting that chronic use causes the colonic tissues to get worn out over time and not be able to expel stool due to long-term overstimulation.vivii Both oral (sodium phosphate and anthraquinones) and rectal (bisacodyl) administration of anthraquinones have been reported to cause colon damage.viii,ix Thus, all attempts should be made to move to bulk-forming laxatives and refrain from chronic use of stimulant laxatives.

Signs and symptoms of cathartic colon include chronic constipation, bloating, and a feeling of fullness, abdominal pain, and incomplete fecal evacuation.

Melanosis coli

What is Melanosis coli?

Melanosis Coli is asscoiated with the long term use of stimulant laxatives

Melanosis coli in the above picture is the dark circular looking area. This picture of melanosis coli was apparently taken from the wikipedia commons, where it’s license for use can be found.

A common finding reported with chronic use of anthraquinone laxatives is increased pigmentation of the intestinal mucosa called melanosis coli. Melanosis coli usually develops 9 to 12 months after the daily use of anthroquinone-containing laxatives, and is diagnostic of laxative abuse.

While this has been determined to be a benign condition that decreases over time with discontinuation of stimulant laxatives,xxi it often alters the ability to diagnose other colon problems.

Melanosis coli has been observed more frequently in patients with colorectal cancer although the significance of this finding is unclear.xii


Do Stimulant Laxatives Cause Colorectal Cancer?

There is no evidence to support the idea that anthroquinone stimulant laxatives cause colorectal cancer.xiii

However, more individuals with colorectal cancer display signs of stimulant laxative abuse than individuals without colorectal cancerxiv

In a prospective study of 1095 patients, the incidence of melanosis coli was 18.6% for patients with colorectal cancer. As discussed earlier, melanosis coli is a fairly reliable marker of chronic stimulant laxative abuse (>9 to 12 months).xv Thus, a significant number of patients with colorectal cancer were chronically using stimulant laxatives. In fact, all patients with melanosis coli acknowledged abuse of anthraquinones for between 10 and 30 years.


How Long Can Stimulant Laxatives Be Used?

Stimulant laxatives are traditionally advocated for short-term use (< 2 weeks) because they can damage the colon, cause melanosis coli and cause laxative dependence (see below).

But most warnings against over use of stimulant laxatives are, I think, aimed at people who might use them occasionally without knowing why they are constipated and end up using them more and more without ever getting checked out. Then, if one day what you have is a bowel obstruction or colon cancer, you might have put off seeing a doctor and instead relied upon the laxatives for symptom control for much too long.

That said, if you know that your gut is in good condition, you should know that it is common practice in pain management centers to recommend stimulant laxatives for DAILY use in patients who are on long-term opiates for pain control. Opiates slow down peristaltic activity so even if your stool is softer, that won’t necessarily help it to come out any easier (that’s where a stimulant laxative comes in).

Many patients who were on this regimen, who no longer needed opiates, returned to normal regularity without a problem.

Anthraquinones (20-30 mg sennosides daily) were found to be safe when administered daily to elderly patients with chronic constipation for 6 months.

In short, don’t be unduly concerned that you have had to use a stimulant laxative a few times in the past few weeks. Nevertheless, all attempts should be made to move to bulk-forming laxatives to avoid potential dangers.


How To Take Stimulant Laxatives

When to take stimulant laxatives?

Anthraquinones work within 6 to 12 hours so you should take them at night for an effect the next morning.

How much stimulant laxatives do you take?

Over-the-counter stimulant laxatives are deemed safe and effective when administered in amounts of 20 to 30 mg of sennosides per day.xvi Individual dosages should be the smallest amount possible to achieve the desired effectiveness. Look for products which specify the anthraquinone content whenever possible.

With products whose active components are not listed on the label, be conservative in use. You can always take more if you need it, but you can never take less once you have consumed a dose.

In order to evaluate the dosage of various herbal preparations, it is necessary to know the content of anthroquinones in the crude dried herbs and prepared teas.

Senna teas labeled as laxatives typically contain 7-10 mg of sennosides per cup; a dieter’s tea contains 19 mg/cup.

For how long can you take stimulant laxatives?

Limiting the daily intake of anthraquinones to 20-30 mg and limiting duration of use to less than 9 months may be reasonable to avoid the adverse health consequences related to melanosis coli.

Melanosis coli is usually found after a minimum of 9-12 months of stimulant laxative use.xvii

If after this course of therapy, constipation cannot be relieved by fiber supplementation then stimulant laxatives can be used again after an interval of a few weeks while relying on osmotic laxatives (e.g., lactulose; 10 gm twice daily) as a substitute.

After a break in the use of anthraquinones for several weeks, the colon will return to normal and a course of stimulant laxative therapy can be safely repeated if necessary.


Are Stimulant Laxatives Addictive?

Yes. In Germany, about 80% of people chronically abuse anthroquinone-containing stimulant laxatives.xviii

Since stimulant laxatives do not enter the brain, there is no pharmacologic basis for addiction. However, there are people abusing stimulant laxatives and taking exaggerated, diarrhea-promoting doses for extended periods of time in the belief that it contributes to weight loss or from a false belief that frequent bowel movements are necessary.


What Is and What Causes Laxative Dependence?

After using a stimulant laxative, it may be several days before a spontaneous bowel movement occurs. You will probably assume that you are constipated and a vicious cycle develops in which you become dependent on the daily use of a stimulant to induce defection.

Chronic use of laxatives is often said to result in habituation, that is, the reduction or even disappearance of a laxative response, and tolerance, the need to increase the laxative dose in order to maintain the desired response. In other words, where one laxative dose produced results, now two, then three doses a day are required.

Laxative dependence may be caused, at least in part, from the destruction of nerves in the colon, dulling the natural responses that stimulate peristalsis. That is, stimulated peristalsis begins to replace natural peristalsis. The link between the use of stimulant laxatives and colon nerve damage or other structural changes has been established in people with chronic constipation who use them routinely. xix

However, laxative dependence may simply be a psychological dependence.


What Should I Do If I Am Dependent On Stimulant Laxatives?


  • Stopping laxatives may be done gradually or by going “cold turkey” (stopping in one day).
  • Changing to products containing psyllium twice a day may help if you gradually withdraw from laxatives.
  • Also, drink lots of water (6-8 glasses a day) and eat salad with extra ingredients like canned kidney beans or green beans.
  • Dried prunes are good too. Just don’t eat too many of them.
  • Vitamin supplementation and maybe some acidophollis or probiotics to help reestablish your intestinal flora may also be good since your body has been depleted of many nutrients.
  • Withdrawal symptoms may include nausea, constipation, bloating or gas. Some people even report feeling “uncomfortable and depressed”. These symptoms will stop as your body recovers and learns how to regulate itself again.


Recommendations for using laxatives

  • Bulk laxatives are the safest laxative for most individuals and should be considered first in the way of treatment for constipation if lifestyle options do not give adequate relief. Consider psyllium (5g twice a day).
  • If you don’t have a response to bulk laxatives, try an osmotic laxative such as lactulose, or polyethylene glycol. The dose should be adjusted until soft stools are attained.
  • Stimulant laxatives should be reserved for individuals with severe constipation who don’t respond to fiber or osmotic laxatives, for example, individuals receiving opioids for pain management.
  • If you must take a stimulant laxative, limit the daily intake of anthraquinones to 20-30 mg and the duration of continuous therapy to less than 9 months.
  • Remember that herbal stimulant laxatives are not reviewed or approved by the US Food and Drug Administration, and that many questions regarding their efficacy and safety profiles remain unanswered.
  • Stimulant laxatives are contraindicated in cases of bowel obstruction, acute intestinal inflammation and abdominal pain of unknown origin.
  • They should not be used in children under 12 or in pregnant or nursing mothers.
  • If you suffer from long-term constipation, see your physician to rule out other gastrointestinal disorders such as defecatory disorders, fecal impaction and colorectal cancer.


References Used for this article on stimulant laxatives

i Lembo A, Camilleri M. Chronic constipation. N Engl J Med 2003; 1360-8.

ii Shelton MG. Standardized senna in the management of constipation in the peurperium. S Afr Med J 1980; 57: 78-80.

iii Sik JJ, Ehrenpreis ED, Gonzalez L, Kaye M, Breno S, Wexner S, Zaitman DBS, Secrest K. Alterations in colonic anatomy induced by chronic stimulant laxatives: The cathartic colon revisited. J Clin Gastroent 1998; 26: 283-286.

ivSpeare GS. Melanosiscoli. Experimental observations on its production and elimination in twenty-three cases. Am J Surg 1951; 82: 631-7.

v Siegers C-P, von Hertzberg-Lottin E, Otte M, Schneider B. Anthranoid laxative abuse – a risk for colorectal cancer? Gut 1993; 1099-1101.

vi Riemann JF, Schmidt H, Zimmermann W. The fine structure of colonic submucosal nerves in patients with chronic laxative abuse. Scand J Gastroenterol 1980; 15: 761-8.

vii Riemann F, Schmidt H. Ultrastructural changes in the gut automonic nervous system following laxative abuse and in other conditions. Scand J Gastroenterol 1982; 71: 11-24.

viii Meisel JL, Bergman D, Graney D, et al. Human rectal mucosa: Proctoscopic and morphological changes caused by laxatives. Gastroenterology, 1977; 72: 1274-1279.

ix Riecken EO, Zeitz M, Emde C, et al., The effect of an anthraquinone laxative on colonic nerve tissue: a controlled trial in constipated women. Z Gastroenterol 1990; 28: 660-664.

xSpeare GS. Melanosiscoli. Experimental observations on its production and elimination in twenty-three cases. Am J Surg 1951; 82: 631-7.

xi Willems M, van Buuren HR, de Krijger R. Anthranoid self medication causing rapid development of melanosis coli. Neth J Med 2003; 61: 22-4.

xii Siegers C-P, von Hertzberg-Lottin E, Otte M, Schneider B. Anthranoid laxative abuse – a risk for colorectal cancer? Gut 1993; 1099-1101.

xiii Borrelli R, Aviello G, Capasso R, Capasso F. Senna: a laxative devoid of carcinogenic effects. Arch Toxicol 2006; 81: 873.

xiv Siegers C-P, von Hertzberg-Lottin E, Otte M, Schneider B. Anthranoid laxative abuse – a risk for colorectal cancer? Gut 1993; 1099-1101.

xv Speare GS. Melanosis coli: experimental observations on its production and elimination in 23 cases. Am J Surg 1951; 81: 631-7.

xvi Loscutoff S. Adverse reactions cause the department of health services to require a label notice on foods and dietary supplements containing ingredients with stimulant laxatives effects. California Morbidity, 1998 (September): 1-2.

xvii Siegers CP et al. Anthranoid laxative abuse- a risk factor for colorectal cancer? Gut 1993; 34: 1099-1101.

xviii Van Gorkom BAP, De Vries EGE, Karrenbeld A, Kleibeuker JH. Review article: anthranoid laxatives and their potential carcinogenic effects. Aliment Pharmacol Ther 1999; 13: 443-452.

xix Preston DM, Lennard-Jones JE. Severe chronic constipation of young women: “Idiopathic slow transit constipation”. Gut 1986; 27: 41-8.


Research and write by Dr. Annette Kirchgessner, a medical university Professor in a Dept of Gastroenterology, with a Phd (Neuroscience), minor editing by Donald Urquhart.


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