Treating Constipation with Laxatives

Before heading to the laxative aisle at your local pharmacy to self-treat constipation, it’s important to be informed. With the many varieties and types of laxatives and therapies available, choosing the best one for your body’s needs, while avoiding those that are too aggressive, requires knowledge and understanding. Also, as with all treatments, proper use will help to avoid unwanted side effects.

Normally, if you’re eating a diet high in insoluble fibre, drinking at least 6-8 cups (250mL or 8oz) of liquids a day, and exercising daily, this is enough to maintain a healthy, constipation-free digestive system. Of course, many of us sometimes deviate from this and find that constipation is a problem. Some people with conditions such as diabetes or Parkinson’s disease are more likely to experience constipation. Additionally, some drugs cause constipation, for example, the codeine contained in many combination-type pain medications (e.g., Tylenol® #1, 2, or 3). However, when chronic constipation occurs, it’s possible that diet and lifestyle regimes may not be enough to remain symptom free without the assistance of over-the-counter or prescription laxatives.

Whether you need a short-term solution for constipation in an otherwise normal digestive tract, or you need relief on a regular basis, as prescribed by a healthcare professional for a specific situation, the following is a list of the different types of laxatives and treatments available. It’s best if your decision is guided by your healthcare provider so you can make an informed choice that is most suitable for you.


Your body does not digest bulk-forming laxatives; instead, the fibre they contain absorbs and retains a large quantity of fluid, thereby forming a soft, bulky stool (formed feces). The bulky size stimulates the intestinal muscles to naturally contract (peristalsis), causing digestive contents to move along, leading to an easier bowel movement. It can take anywhere from about 12 hours to 3 days for bulk-forming laxatives to show results, depending on individual digestive system transit times, so this laxative type will not provide immediate relief of constipation. They are best to use for ongoing digestive regularity and are helpful for conditions such as diverticular disease, irritable bowel syndrome, and hemorrhoids. Although bulk-forming laxatives are safe for long-term use and are usually well tolerated, sometimes these products can cause bloating, intestinal gas, cramping, and/or increased constipation, especially if you don’t consume enough water. To help prevent side effects, start consuming these products slowly, gradually increasing each dose while making sure to drink plenty of extra water. Examples of bulk-forming laxatives are psyllium (Metamucil®), inulin (Metamucil® Simply Clear), wheat dextrin (Benefibre®), methylcellulose (Citrucel®), and polycarbophil (FiberCon®, Prodiem®).

Stool Softeners

Stool softeners enable easier incorporation of water into the stool to keep it soft and easier to pass. By making the stool softer, it reduces or eliminates the need to strain, so stool softeners may be recommended after childbirth or surgery, or during a bout of hemorrhoids. Some individuals may form a tolerance to softeners and may require higher doses over time. Stool softeners do not directly affect the digestive tract muscles and are safe to use in pregnant women and elderly people. Some experts do not classify stool softeners as laxatives. An example of a stool softener is docusate sodium (Colace®). Long-term use, if bowel movements remain comfortable, is acceptable.


Lubricant laxatives simply coat the colon and stool in a waterproof film allowing it to remain soft and easier to slip through the intestine while retaining its moisture, usually within 6-8 hours. Don’t use these products for longer than a week, as some have been shown to cause vitamin deficiencies and they might also interact with some medications by affecting how the body absorbs them. Pregnant women and persons who have difficulty swallowing should avoid lubricant laxatives. An example of a lubricant laxative is mineral oil.


Stimulants increase muscle contractions of the digestive system (peristalsis) to move contents along, facilitating a shorter colonic transit time. Although individuals often use this type of laxative as a form of self-treatment, they should be reserved for use in extreme conditions and only under the recommendation or supervision of a pharmacist or physician. A risky side effect is that they may cause the colon to stop functioning correctly (cathartic colon), which often occurs with daily use after which the body becomes dependent on the stimulant laxative for normal peristaltic activity. Stimulants taken orally often take 6-10 hours to have an effect. For patients who have chronic constipation caused by irritable bowel syndrome, stimulants may be the only solution but, even then, should only be used for a short term. This form of laxative is not recommended for pregnant women. Examples of stimulants are bisacodyl (Ex-lax®, Dulcolax®), castor oil, and senna (Senokot®).


Osmotic laxatives encourage bowel movements by drawing water into the bowel from the nearby tissue (intestinal lumen) thereby softening the stool. Some of these laxatives can cause electrolyte imbalances as they draw out nutrients and other contents with the water, which increases thirst and dehydration. There are four main types of hyperosmotics: saline, lactulose, polymer, and glycerine.

Saline laxatives are essentially salts in liquid; they rapidly empty all the contents of the bowel and are not intended for long-term use or for pregnant women. These generally work within 30 minutes to 3 hours. Examples of saline laxatives are citrate salts (Royvac®), magnesium preparations (Phillips’® Milk of Magnesia), sulfate salts, and sodium phosphate.

Lactulose laxatives are a sugar-like agent that work similarly to the saline laxatives but at a much slower rate and are sometimes used to treat chronic constipation. Often they will have an effect in 6 hours, but can take up to 2 days. Lactulose comes in a liquid form taken orally and several manufacturers make it.

Polymer laxatives consist of large molecules that cause the stool to hold and retain water. They are usually non-gritty, tasteless and are well-tolerated for occasional constipation. Results can be expected within 6 hours, but it can take longer depending on the dose. An example of a polymer laxative is polyethylene glycol (Lax-A-Day®, PegaLAX®, RestoraLax®).

Glycerine is available as a suppository and mainly has a hyperosmotic effect but it may also have a stimulant effect from the sodium stearate used in the preparation. Glycerine is available as a laxative through several manufacturers.


An enema may be preferred occasionally to relieve severe constipation or to empty the bowel prior to surgery. This method involves insertion of liquid, usually water or hyperosmolar salt solution, described above, which acts as a mechanical stimulant and osmotic, into the rectum via the anus. You can purchase prepared enemas, an enema bulb, or fountain syringe at your local pharmacy to use for this sole purpose. Typically, after holding the liquid in place for a few minutes, there is an intense urgency to move the bowels. An enema may cause uncomfortable bloating and cramping; however, it usually leads to urgent elimination of the contents of the rectum and colon, doing away with constipation.

Colonic Irrigation

It is important to note that although many holistic advertising campaigns recommend colonic irrigation to ‘re-program the bowel’s motility and assist in the reduction of constipation’, there is no medical evidence that colonic irrigation or colon cleansing is effective in either of those claims, or the myriad of other cure-alls promoted on late-night television shows. Physicians and other healthcare providers associated with the GI Society do not recommend the use of colonic irrigation. In fact, these procedures could negatively affect the natural pH balance of the colon, cause electrolyte imbalances, upset the natural bacterial and yeast milieu necessary for good digestion, and could even cause permanent physical damage to the bowel. This approach may worsen existing digestive conditions.

Pregnancy and Childbirth

A common complication of pregnancy is constipation. If making the appropriate dietary and lifestyle adjustments to reduce constipation for a pregnant or nursing woman do not work, then her primary physician may recommend either stool softeners or bulk-forming laxatives, depending on the frequency and duration of constipation. It is very important that she drink plenty of water while taking a laxative, as some can be high in salt and might dehydrate the expectant or nursing mother. Others require sufficient fluid intake to work properly, as with bulk-forming laxatives. Always consult a pharmacist or physician before taking medications while pregnant or nursing, as some formulas of over-the-counter or prescription laxatives can negatively affect the infant. By preventing straining during a bowel movement, dietary fibre and bulk-forming laxatives can also assist in the prevention of hemorrhoids, a common pregnancy and delivery concern.

Proper Use of Laxatives

It is important for individuals to follow the instructions given by a healthcare provider and those supplied by the product manufacturer when taking an over-the-counter laxative. Unless otherwise directed by a medical professional, remember that over-the-counter and prescription laxatives are only intended for short-term use and you should not exceed the dosage on the label.

With all types of laxatives, it is important to consume at least 6-8 cups (250mL or 8oz) of liquids (preferably water) every day plus an additional glass with every laxative dose taken, unless otherwise advised by your healthcare provider. As described above, laxatives often draw fluid into the digestive system to soften the stool and/or pass it out with the bowel movement. Ensure plenty of fluid intake to prevent dehydration.

Laxative abuse can lead to serious dysfunction of bowel motility such as intestinal paralysis, cathartic colon, lazy or laxative gut, irritable bowel syndrome, pancreatitis, and other problems. Using laxatives regularly, except for bulk-forming agents and stool softeners, can lead to these problems. Therefore, it is important to use laxatives in moderation and under the supervision of a physician or other regulated healthcare provider. If you have chronic constipation, where it is a daily issue or occurs more than once a week, then seek the care of a medical professional before self-treating with over-the-counter laxatives.

Alan Low, BSc. (Pharm.), Pharm. D., RPh, ACPR, FCSHP, CCD
Pharmacist and Clinical Associate Professor,
Faculty of Pharmaceutical Sciences, UBC
First published in the Inside Tract® newsletter issue 174 – 2010
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