Constipation remedies (a 2021 pharmacist review)

Make sense of over the counter remedies to treat constipation


Ok, so you’re constipated?  You decide to go to the pharmacy and you are looking at a massive wall of laxatives and are overwhelmed!  So many choices! So many brands !  Do you take a pill? A powder? A drink?  A suppository?     You could ask the pharmacist, but he’s your friend’s dad and do you really want to get into this kind of discussion with him?  No I did not think so!

Yes, there are a lot of choices and if you are lucky enough to stumble on this post, I will try to make sense of it-

Let’s dive right in:

There are 4 main groups of laxatives that you will find available without a prescription (aka OTC over the counter):

  1. Bulk-forming,
  2. Emollient,
  3. osmotic and stimulant; h
  4. high-dose osmotic agents that can also be classified as purgative laxatives

Other drug classes include that require prescription:

mu-opioid receptor antagonists (e.g., methylnaltrexone, naloxegol), prokinetic agents (e.g., domperidone, erythromycin, prucalopride), guanylate cyclase C-agonists (e.g., linaclotide) and serotonin 5-HT4 receptor agonists (e.g., prucalopride).  We will not get into those in this blog but will provide a link to the article here.

  1. Bulk-Forming Laxatives

Bulk-forming laxatives laxative increase stool volume and are considered the safest agents suitable for long- term use.

Their fermentation in the colon leads to gas formation, water

retention and wall stress, which stimulate motility. When you add bulk in the colon, it naturally stimulates movement in your gut.

Misterpharmacist Tip: Each dose of a bulk-forming laxative should take at least 250 mL of water or juice to prevent fecal impaction and/or esophageal obstruction. Do not use if your (or your “patient”)  is dehydrated or fluid restricted, as impaction may result – that’s a blockage in your gut from dried stool- not good!

On average, the bulk-forming laxative requires 12-72 hours for onset of effect so don’t think of using a bulk laxative if you want immediate relief!.

Psyllium improves stool frequency and consistency and bran reduces the use of laxatives in the elderly.

Inulin is a fermentable, nonviscous soluble fibre that has little water holding capacity and has less laxative benefit than viscous fibre. However, 3-4 g of chicory inulin has been proven to increase the number and softness of stools.

Although there is insufficient evidence regarding the efficacy of calcium polycarbophil and methylcellulose in the management of constipation, these agents are still recommended if patients cannot use or tolerate other bulk-forming laxatives.

Misterpharmacist Tip:  Fibre shows consistent beneficial effect for relieving overall symptoms and bleeding in the treatment of symptomatic hemorrhoids.  So if you tend to have hemorrhoids, use fibre regularly

2. Emollients (Stool Softeners)

Stool softeners (e.g., docusate sodium or docusate calcium) act as surfactants to soften the stool by allowing the mixing of aqueous and fatty substances.

Did you know? Not many health professionals do:  Although used commonly for many years, the supporting evidence for effectiveness is lacking and they do not improve symptoms of chronic Constipation! There is some weak evidence exists supporting the use of stool softeners post-urogynecological surgery and post myocardial infarct. Now there is something to impress your pharmacist or doctor with if they send you away with a recommendation for Colace®.

Heavy mineral oil is not generally recommended anymore due to risk of lipid aspiration and binding of fat-soluble medications.    Lipid aspiration is bad – it basically means that you can have some mineral oil seep into your lungs especially if you are bed ridden which needless to say is pretty bad on its own and also if you take mineral oil regularly, you will not be able to absorb Vitamins like A, D, E and K as they will dissolve in the mineral oil and you end up pooping them out.

Some physicians will recommend mineral oil or mineral jelly in toddlers.  It has shown to be better to senna-based laxatives for frequency and stool consistency and less effective to osmotic agents, which have fewer risks. More on that a little below.

3. Osmotic Laxatives

That sounds like quite a fancy word “osmotic”.    It comes from the word osmosis-  remember high school chemistry class?  I know, it’s very far away….

Osmotic agents contain poorly absorbed ions or molecules that create an osmotic gradient and retain

water within the intestinal lumen: the increased pressure on the lumen wall induces gastric motility.

Polyethylene glycol (PEG) and lactulose are examples of osmotic constipation remedies.  

Misterpharmacist Pro Tip: Sprinkle your PEG in soft foods as it practically has no taste!   I like to put mine in yogurt or pudding!  I have also patients that add it to their soup!

PEG is a safe, effective and well-tolerated agent and causes less flatulence and bloating in adults compared with other osmotic laxatives. PEG is superior to lactulose ) in outcomes of stool frequency per week, stool form and consistency, relief of abdominal pain and need for additional products. PEG is considered more palatable than lactulose. I find lactulose way too sweet!  Daily use of PEG (up to 6 months) is safe and effective and may facilitate the discontinuation of other laxatives. However, as many as 40% of patients may experience diarrhea with PEG or lactulose. Lower doses help prevent bloating, cramping, flatulence and electrolyte abnormalities.

PEG may also be effective in the management of opioid-induced constipation. Both are safe for use in diabetics as the osmotic agents (e.g., lactulose) are not absorbed but remain in the intestinal lumen. Osmotic laxatives require 24-72 hours for onset of action and are best used regularly rather than as needed, as onset of action is delayed due to mechanism.

Glycerin suppositories act osmotically and have a quicker onset of action (approximately 15-30 minutes). They are less effective if the stool is dry and hard or higher in the colon.

Misterpharmacist Pro tip: A Glycerin suppository should be moistened with lukewarm water by running it under a running tap right before insertion; they should be retained as long as possible. So pucker up and try to keep it in at least 10 minutes for a more complete effect.

There is some evidence that milk of magnesia (ex Phillips ®) can be used for chronic constipation in patients with normal renal function. Limitations include frequent diarrhea, multiple electrolyte abnormalities (e.g., hypomagnesemia, hyperphosphatemia, hypercalcemia, hyponatremia, hypokalemia) and hypovolemia. These side effects may occur even in the absence of pre-existing renal failure. They should be administered with sufficient water to prevent dehydration. Due to lower level of proof that it works and effect on electrolytes, milk of magnesia should be considered a second-line osmotic laxative.


Both high-volume PEG with added electrolytes and low-volume PEG without electrolytes have been shown to be safe and effective when used at high doses as purgatives; however, repeated or prolonged

use of high-volume PEG with electrolytes may result in electrolyte imbalance. Caution should also be exercised in the use of PEG with electrolytes If you have renal impairment, take diuretics and in kids and older patients.

Oral sodium phosphate products should not be used as purgatives since they may cause serious electrolyte, kidney, cardiovascular and neurologic problems, but they are still considered safe and effective for laxative use. Magnesium citrate is generally reserved for bowel cleansing.

Osmotic laxatives alone or in combination with stimulants are most commonly used before surgery or colonoscopy or gastroscopy.

4. Stimulant Laxatives

This group of laxatives (e.g., bisacodyl, senna, sodium picosulfate) increase colonic movement (“peristalsis”) by producing rhythmic muscle contractions in the intestines and may be recommended if osmotic laxatives fail or are not tolerated.

 All 3 medications are prodrugs. Senna is activated in the large

bowel whereas bisacodyl and sodium picosulfate are activated in the alkaline medium of the small intestine. Bisacodyl has an NNT = 3 based on a moderate level of evidence. By contrast, there is

low-quality evidence to support the use of sennosides.

Higher level of abdominal cramping may ensue with bisacodyl.

Limiting their use helps minimize melanosis coli (rare), abdominaldiscomfort, electrolyte imbalances, allergic reactions and hepatotoxicity. Stimulant laxatives are likely safe in the treatment of chronic constipation. Some evidence supports the short-term (4 weeks) efficacy and safety of bisacodyll69! and sodium picosulfate in chronic constipation.

Continuous daily usage may cause hyponatremia, hypokalemia and dehydration.

MisterPharmacist Pro Tip:  Stimulant laxatives are usually administered at bedtime due to 6-12 hour delay in onset

MisterPharmacist added Pro tip: Stimulant laxatives are the constipation remedies of choice for opioid-induced constipation. So if you are on a narcotic painkiller, make sure you take one of there types of laxatives to keep you bowel moving.

Castor oil is no longer recommended as a laxative and is contraindicated in pregnant and elderly patients. It produces abdominal cramping and pain, stimulates uterine contractions during pregnancy and can be aspirated.


There is only anecdotal evidence for the value of enemas in the management of chronic constipation.

However, many clinicians and patients find them useful and effective for the treatment of acute

constipation and as a means of preparing or cleansing the distal colon for endoscopic or surgical

procedures. Enemas generally have faster onset than suppositories and produce cleansing within an hour of administration.

 They are, however, less socially accepted by North Americans for chronic

constipation and are mainly used for bowel cleansing prior to intestinal procedures.

Caution is warranted when using enemas in the elderly since they are associated with increased mortality.(?)

Soap suds, tap water and milk of molasses enema have fallen out of use due to a high level of colonic irritation.

Instructions for Administering an Enema

The patient should:

■             Lubricate the enema nozzle if it is not pre-lubricated

■             Lie on left side with knees bent

■             Insert the enema nozzle into the rectum, with the nozzle pointing towards the navel

■             Gently squeeze the container until the dose is expelled; if discomfort is felt at this point, the flow is

probably too fast

■             Retain the solution until definite abdominal cramping is felt


Evidence is growing to support the use of probiotics in the treatment of chronic idiopathic constipation. A meta-analysis including 21 studies of 2656 subjects who used probiotics containing

Lactobacillus or Bifidobacterium species showed a mean increase in weekly stool frequency and a mean reduction in intestinal transit time.

Another meta-analysis of 9 studies in elderly patients showed an improvement in constipation of 10-40% with probiotics compared with placebo,

with Bifidobacterium longum the most common strain studied. The lack of heterogeneity among probiotic trials makes it difficult to determine the most beneficial strains, dosage, dosing frequency and duration of treatment.