Magnesium citrate how long

Have you ever purchased Citrate of Magnesia?

Read and follow all directions on the product package. If your doctor has directed you to use this product before surgery or a bowel procedure, he or she should tell you how long before the surgery/procedure you should take this product. If you are uncertain about any of the information, consult your doctor or pharmacist. To improve taste, this product may be chilled in the refrigerator before use. Do not freeze.

Dosage is based on your medical condition, age, and response to treatment. Drink a full glass of water (8 ounces or 240 milliliters) after taking this product unless otherwise directed by your doctor. Doing so will help prevent serious side effects (e.g., a loss of too much body water-dehydration).

If this product is used too frequently, it may cause loss of normal bowel function and an inability to have a bowel movement without using the product (laxative dependence). If you notice symptoms of overuse, such as diarrhea, abdominal pain, decreased weight, or weakness, contact your doctor promptly.

Avoid taking tetracycline/quinolone antibiotics (e.g., doxycycline, tetracycline, ciprofloxacin) within 2 hours before or after this product. Doing so may decrease the effect of the antibiotic.

If this product fails to produce a bowel movement, or if you think you may have a serious medical problem, contact your doctor promptly.

Magnesium Citrate for Constipation

Constipation can be a thoroughly uncomfortable experience, yet is surprisingly common. Scientific studies suggest that up to 20% of the population may suffer from constipation at one time or another.

Generally speaking the evidence suggests that the chance of suffering from constipation increases with age, and is far more common in women than men. It’s little wonder, then, that so many people are searching for effective constipation remedies like magnesium citrate.

What is Constipation?

Doctors have long noted that many people define constipation differently. At its most basic, constipation is defined as a difficulty in passing stools effectively. However, there are a range of elements that may indicate a case of constipation including:

  • Hard or lumpy stools
  • Difficulties with passing stools
  • Excessive straining or discomfort while on the toilet
  • A feeling of being unable to pass all material in one go

If you are suffering from any of these symptoms then you may well be experiencing constipation. Fortunately, there are a number of different solutions that can help with the problem, and magnesium is one of the best-known of these.

What Causes Constipation?

A range of different factors can impact our digestive system. While the following list is not exhaustive, some common causes of constipation can include:

  • Stress
  • Unbalanced diet (for example one deficient in fibrous material)
  • Lack of exercise
  • Dehydration

In many cases the root cause of constipation remains a mystery, and many people find the symptoms are transient and disappear naturally after a period of time.

If you find yourself suffering regularly then it is advisable to seek guidance from your doctor, who will be able to check that your constipation is not an indication of more serious health issues.

What is Magnesium Citrate?

Magnesium is a tremendously common element. It is considered to be the ninth most abundant element in the universe, and the fourth most abundant mineral in the body.

It has been used for years as a remedy for constipation and is now available in a range of different forms. Some of the most common forms of magnesium used for medicinal purposes include magnesium hydroxide (better known as “milk of magnesia”) and magnesium sulphate (also known as Epsom salt). This article, however, focuses on magnesium citrate.

As the name suggests, magnesium citrate comprises of magnesium molecules bound to citric acid. The reason for magnesium citrate’s popularity in recent years has been its high bioavailability. The combination of magnesium and citric acid seems to make it more easily absorbed by the body, and so can boost the benefit of taking this supplement.

How Does Magnesium Help With Constipation?

Magnesium has a long history of use when it comes to digestive problems. Two of the most common therapeutic uses relate to the treatment of constipation and colonic cleansing, particularly before surgical procedures. Generally speaking any product designed to treat the condition we know as constipation is known as a laxative.

There are a host of different laxatives, which are often grouped by their specific mode of action. Magnesium in general, and magnesium citrate in particular, belong in a category known as “osmotic laxatives”. In essence, magnesium citrate functions by drawing water into the gut from the rest of the body. When this happens stools not only travel more easily but can absorb this water itself, making for easier and more comfortable passing.

Indeed, studies have found that the consumption of just 3.5g of magnesium reduced urinary volume in volunteers by almost a third, as this moisture is redirected into the intestine and lost through the stool. It is important to understand this mode of action because dehydration can result in constipation, as well as a range of other potential health issues.

Therefore if you opt to use magnesium citrate for constipation you should also be certain to drink suitable volumes of water to prevent the risk of dehydration and to allow the supplement to do its job effectively.

What Foods Contain Magnesium?

Magnesium is so common that it may be found in a wide range of different foods. In reality, the levels can be quite low and so you may wish to instead consider the use of a supplement to ease symptoms of constipation. As an ongoing treatment for digestive health the following foods may come in handy…

  • Halibut
  • Almonds
  • Cashews
  • Spinach
  • Shredded Wheat
  • Oatmeal
  • Potato
  • Peanuts
  • Wheat Bran
  • Yogurt
  • Bran Flakes
  • Brown Rice
  • Avocado
  • Kidney Beans
  • Banana
  • Whole Wheat Bread
  • Raisins
  • Whole Milk

Alternatively, or additionally, ensure that you’re getting enough fibre in your diet.

How Much Magnesium Citrate Should I Take for Constipation?

Numerous studies have aimed to assess the “optimal” dosage for magnesium citrate. One study provided a range of different permutations to volunteers and found that “faecal weight is proportional to faecal soluble magnesium output”. In other words, the more you take, the greater the impact.

Magnesium citrate, like many other osmotic laxatives, is considered a relatively fast-acting constipation remedy. The scientists in question found that most adults that consume between 2.4 and 4.8 g experience “an evacuation within 6 hours”.

Another study of magnesium’s effect on constipation, this time in children, recommended similar doses and claimed that these should be taken for two or three days, or until the issue is resolved.

Reports on the use of magnesium in Japan suggest rather lower doses are common in the East, with the average treatment dose coming in at 600mg per day, but that under these circumstances treatment is often continued for some weeks with no obvious negative side effects.

One final study suggested that a daily intake of 25ml of magnesium can be beneficial, but that doses of up to 8.7g are commonly used as a “bulk laxative”.

Generally speaking it would seem that starting off with smaller doses makes sense, which can be subsequently increased over time if required.

Our magnesium citrate supplement contains 200mg per tablet. It therefore seems likely that three of these tablets would be a good starting point for constipation treatment. This could be increased subsequently if the issue does not resolve itself. It has been suggested by experts that consuming magnesium citrate with a glass of water or juice will help it to be absorbed more effectively.

What are the Side Effects of Magnesium Citrate?

Magnesium citrate is considered to be quite a safe remedy for constipation because it works within the intestine rather than in the body at large. Side effects therefore tend to be minimal, especially when taken in moderation and for short periods of time.

Most side effects are minor and soon pass once supplementation ceases. Possibly the most common potential side effect of supplementing with magnesium citrate is that the volume of moisture drawn into the intestines can actually moisten stools too much, leading to short-term diarrhoea.

Used excessively, some experts have also raised concerns about the potential for electrolyte imbalances thanks to the osmotic properties of magnesium. Some experts claim that long term use has the potential to result in magnesium toxicity.

It is therefore recommended that you closely follow the dosing instructions on your chosen supplement, and if side effects arise you should discontinue use and seek advice from your doctor.

What Other Remedies Could I Try for Constipation?

Magnesium citrate is just one potential treatment for constipation. A range of other options may also offer benefits, and some individuals opt to experiment with different alternatives to find the combination that works best for them.

Three of the most popular supplements for recurring constipation are:

Psyllium Fibre – A rich source of fibre, ideal for encouraging more regular toilet visits. Learn about psyllium fibre here.

Glucomannan – Also known as konjac fibre, glucomannan is a popular source of soluble fibre. Take this supplement with a large glass of water, which it will absorb in the gut, turning into a thick gel that eases stools along their journey. Learn about glucomannan here.

Probiotics – Some experts believe that an imbalance in the bacteria that line the gut wall can lead to digestive problems like diarrhoea and constipation. Indeed, some IBS sufferers regularly use probiotics to help rebalance their microflora.

Try to bulk up the “friendly bacteria” in your digestive tract and you may find that constipation becomes a thing of the past. Learn about probiotics here.


Magnesium has a long pedigree of use for resolving cases of constipation, and magnesium citrate is considered one of the most easily-absorbed forms. It tends to be fast acting, so keeping a tub in your cupboard at home can represent an excellent “on demand” solution for constipation sufferers.

Shop for magnesium citrate here.


Magnesium citrate


Are you a new drug developer? Contact us to learn more about our customized products and solutions. Stay in the know! As part of our commitment to providing the most up-to-date drug information, we will be releasing #DrugBankUpdates with our newly added curated drug pages. #DrugBankUpdates Name Magnesium citrate Accession Number DB11110 Type Small Molecule Groups Approved Description

Magnesium citrate is a low volume and osmotic cathartic agent. The cathartic action works primarily through the high osmolarity of the solution which draws large amounts of fluid into space where is used.5 Magnesium citrate is considered by the FDA as an approved inactive ingredient for approved drug products under the specifications of oral administration of a maximum concentration of 237 mg.7 It is also considered as an active ingredient in over-the-counter products.6

Structure Download Similar Structures

Structure for Magnesium citrate (DB11110)

× Close Synonyms

  • Magnesium dicitrate
  • Trimagnesium citrate
  • Trimagnesium dicitrate

Active Moieties

Name Kind UNII CAS InChI Key
Magnesium cation ionic T6V3LHY838 22537-22-0 JLVVSXFLKOJNIY-UHFFFAOYSA-N
Magnesium unknown I38ZP9992A 7439-95-4 RSHAOIXHUHAZPM-UHFFFAOYSA-N

Over the Counter Products

Name Dosage Strength Route Labeller Marketing Start Marketing End
Unlock Additional Data
BET-R-PREP Magnesium Citrate Oral Solution 1.745 g/1mL Topical Satius Pharmaceuticals, Llc 2017-11-18 Not applicable US
Citrate of Magnesium Liquid 1.745 g/29.6mL Oral Physicians Total Care, Inc. 2003-01-29 Not applicable US
Citroma Liquid 1.745 g/29.61mL Oral Wal-Mart Stores, Inc 2012-03-21 Not applicable US
Citroma Liquid 1.745 g/29.6mL Oral Vi Jon, Inc 1989-07-15 Not applicable US
Citroma Liquid 1.745 g/29.6mL Oral Walgreen Co 2018-02-18 Not applicable US
Citroma Liquid 1.745 g/29.6mL Oral Strategic Sourcing Services LLC 2018-02-18 Not applicable US
Citroma Liquid 1.745 g/29.61mL Oral Western Family Foods 1990-04-15 Not applicable US
Citroma Liquid 1.745 g/29.6mL Oral Major Pharmaceuticals 2018-02-18 2018-03-28 US
Citroma Liquid 1.745 g/29.6mL Oral Wakefern Foods Corporation 1989-07-15 Not applicable US
Citroma Liquid 1.745 g/29.6mL Oral Krogers 2018-02-18 Not applicable US

Additional Data Available

  • Application Number Application Number

    A unique ID assigned by the FDA when a product is submitted for approval by the labeller.

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  • Product Code Product Code

    A governmentally-recognized ID which uniquely identifies the product within its regulatory market.

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Mixture Products Unapproved/Other Products Categories UNII RHO26O1T9V CAS number 3344-18-1 Weight Average: 451.113
Monoisotopic: 449.9621801 Chemical Formula C12H10Mg3O14 InChI Key PLSARIKBYIPYPF-UHFFFAOYSA-H InChI InChI=1S/2C6H8O7.3Mg/c2*7-3(8)1-6(13,5(11)12)2-4(9)10;;;/h2*13H,1-2H2,(H,7,8)(H,9,10)(H,11,12);;;/q;;3*+2/p-6 IUPAC Name trimagnesium(2+) bis(2-hydroxypropane-1,2,3-tricarboxylate) SMILES …OC(CC()=O)(CC()=O)C()=O.OC(CC()=O)(CC()=O)C()=O



Magnesium citrate has been used in bowel preparations prior to a colonoscopy as a cathartic agent.5

It is also used in over-the-counter products to relieve occasional constipation.8

Magnesium citrate can be one of the forms used for the administration of dietary supplements.9

Associated Conditions

  • Migraine


The onset of action can be as early as 30 minutes after administration with a mean onset time of approximately 2 hours and a maximum action of 4 hours. The effect of magnesium citrate is highly dependent on the individual’s hydration status.5

Mechanism of action

It mainly works through its property of high osmolality which will draw large amounts of fluid into the colonic lumen. There is also a possible stimulation of fluid excretion by cholecystokinin release and activation of muscle peristalsis.5

Unlock Additional Data Additional Data Available Adverse Effects

Comprehensive structured data on known drug adverse effects with statistical prevalence. MedDRA and ICD10 ids are provided for adverse effect conditions and symptoms.

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Structured data covering drug contraindications. Each contraindication describes a scenario in which the drug is not to be used. Includes restrictions on co-administration, contraindicated populations, and more.

Learn more Additional Data Available Blackbox Warnings

Structured data representing warnings from the black box section of drug labels. These warnings cover important and dangerous risks, contraindications, or adverse effects.

Learn more Absorption

Mean plasma concentration of magnesium after administration of oral doses of magnesium citrate are reported to be of around 0.7 mmol/L and the concentration in saliva rested in 0.28 mmol/L. In reports, it has also been proven that the absorption and bioavailability of magnesium are greater when administered in the form of magnesium citrate when compared with other forms such as magnesium ocude.1

Volume of distribution Not Available Protein binding

Magnesium, once ionized, is highly bound to plasma proteins and it can represent even 90% of the magnesium found in blood plasma.3

Metabolism Not Available Route of elimination

After oral administration of magnesium citrate, there is a 40% increase in urine excretion of magnesium.2 Magnesium citrate is also widely eliminated via the feces because, when present in the bowel, it relaxes the bowel and pulls water into the intestine which increases bowel movement and a significant portion of this agent gets excreted by this via.10

Half life

The study of the half-life of magnesium citrate is very difficult due to the half-life of the available isotopes for magnesium.4

Clearance Not Available Toxicity

The occurrence of overdose with magnesium citrate is very unlikely but some of the signs of the presence of overdose are diarrhea or severe stomach pain.8

Affected organisms

  • Humans and other mammals

Pathways Not Available Pharmacogenomic Effects/ADRs Not Available


Drug Interactions This information should not be interpreted without the help of a healthcare provider. If you believe you are experiencing an interaction, contact a healthcare provider immediately. The absence of an interaction does not necessarily mean no interactions exist.

  • All Drugs
  • Approved
  • Vet approved
  • Nutraceutical
  • Illicit
  • Withdrawn
  • Investigational
  • Experimental
Drug Interaction
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1alpha-Hydroxyvitamin D5 The serum concentration of Magnesium citrate can be increased when it is combined with 1alpha-Hydroxyvitamin D5.
1alpha,24S-Dihydroxyvitamin D2 The serum concentration of Magnesium citrate can be increased when it is combined with 1alpha,24S-Dihydroxyvitamin D2.
3-Aza-2,3-Dihydrogeranyl Diphosphate Magnesium citrate can cause a decrease in the absorption of 3-Aza-2,3-Dihydrogeranyl Diphosphate resulting in a reduced serum concentration and potentially a decrease in efficacy.
Acetazolamide The risk or severity of adverse effects can be increased when Acetazolamide is combined with Magnesium citrate.
Aclidinium The therapeutic efficacy of Magnesium citrate can be decreased when used in combination with Aclidinium.
Agmatine The risk or severity of hypotension can be increased when Agmatine is combined with Magnesium citrate.
Alcuronium The therapeutic efficacy of Alcuronium can be increased when used in combination with Magnesium citrate.
Alendronic acid Magnesium citrate can cause a decrease in the absorption of Alendronic acid resulting in a reduced serum concentration and potentially a decrease in efficacy.
Alfacalcidol The serum concentration of Magnesium citrate can be increased when it is combined with Alfacalcidol.
Alfentanil The therapeutic efficacy of Magnesium citrate can be decreased when used in combination with Alfentanil.

Additional Data Available

  • Extended Description Extended Description

    Extended description of the mechanism of action and particular properties of each drug interaction.

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  • Severity Severity

    A severity rating for each drug interaction, from minor to major.

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  • Evidence Level Evidence Level

    A rating for the strength of the evidence supporting each drug interaction.

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  • Action Action

    An effect category for each drug interaction. Know how this interaction affects the subject drug.

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Food Interactions Not Available General References External Links PubChem Compound 6099959 PubChem Substance 347827901 ChemSpider 2925651 ChEBI 131391 ChEMBL CHEMBL3989480 Wikipedia Magnesium_citrate_(3:2) ATC Codes B05CB03 — Magnesium citrate

  • B05CB — Salt solutions

A12CC04 — Magnesium citrate

  • A12CC — Magnesium

A06AD19 — Magnesium citrate

  • A06AD — Osmotically acting laxatives

MSDS (231 KB)

Clinical Trials

Clinical Trials

Phase Status Purpose Conditions Count
1, 2 Completed Treatment Hypertension,Essential 1
2 Completed Diagnostic Bowel preparation therapy / Bowel Preperation / Polyethylene Glycol With Ascorbic Acid / Sodium Picosulfate and Magnesium Citrate 1
2 Completed Treatment Colonoscopy 1
2 Recruiting Treatment Pitt Hopkins Syndrome 1
3 Completed Not Available Bowel Preparation for Colonoscopy 1
3 Completed Supportive Care Colon Adenomas / Colorectal Cancers 1
3 Recruiting Prevention Extreme Immaturity / Magnesium Deficiency / Premature Births 1
4 Active Not Recruiting Treatment Patients Undergoing Elective Colonoscopy 1
4 Completed Not Available Bowel Cleansing Process / Colonoscopy 1
4 Completed Treatment Colon Cleansing 1
4 Completed Treatment Colon Cleansing for Colonoscopy 1
4 Completed Treatment Colonoscopy 2
4 Recruiting Diagnostic Ulcerative Colitis 1
4 Recruiting Prevention Constipation 1
4 Recruiting Treatment Hypomagnesemia 1


Manufacturers Not Available Packagers Not Available Dosage forms

Form Route Strength
Capsule Oral
Powder Oral
Solution Topical 1.745 g/1mL
Liquid Oral
Liquid Oral 1.745 g/29.61mL
Solution Oral 1.745 g/29.61mL
Powder, for solution Oral 16 g/16g
Powder, for solution Oral 17 g/17g
Liquid Oral 1.745 g/29.6mg
Liquid Oral 1.745 g/29.6mL
Liquid Oral 2.62 g/100mL
Liquid Oral 2.65 mg/100mL
Solution Oral 1.745 g/29.6mL
Liquid Oral 2.65 g/100mL
Liquid Oral
Tablet, film coated Oral
Kit Oral
Powder, for solution Oral 17 g/100g
Powder, for solution Oral
Tablet Oral
Kit Oral; Rectal

Prices Not Available Patents Not Available


State Solid Experimental Properties

Property Value Source
melting point (°C) 184 ºC ‘MSDS’
water solubility Partially soluble in cold water ‘MSDS’

Predicted Properties

Property Value Source
Water Solubility 6.34 mg/mL ALOGPS
logP 0.08 ALOGPS
logP -1.3 ChemAxon
logS -1.8 ALOGPS
pKa (Strongest Acidic) 3.05 ChemAxon
pKa (Strongest Basic) -4.2 ChemAxon
Physiological Charge -3 ChemAxon
Hydrogen Acceptor Count 7 ChemAxon
Hydrogen Donor Count 1 ChemAxon
Polar Surface Area 140.62 Å2 ChemAxon
Rotatable Bond Count 10 ChemAxon
Refractivity 68.14 m3·mol-1 ChemAxon
Polarizability 14.25 Å3 ChemAxon
Number of Rings 0 ChemAxon
Bioavailability 1 ChemAxon
Rule of Five Yes ChemAxon
Ghose Filter No ChemAxon
Veber’s Rule No ChemAxon
MDDR-like Rule No ChemAxon

Predicted ADMET features Not Available


Mass Spec (NIST) Not Available Spectra Not Available


Description This compound belongs to the class of organic compounds known as tricarboxylic acids and derivatives. These are carboxylic acids containing exactly three carboxyl groups. Kingdom Organic compounds Super Class Organic acids and derivatives Class Carboxylic acids and derivatives Sub Class Tricarboxylic acids and derivatives Direct Parent Tricarboxylic acids and derivatives Alternative Parents Tertiary alcohols / Carboxylic acid salts / Carboxylic acids / Organic salts / Organic oxides / Hydrocarbon derivatives / Carbonyl compounds Substituents Tricarboxylic acid or derivatives / Tertiary alcohol / Carboxylic acid salt / Carboxylic acid / Organic oxygen compound / Organic oxide / Hydrocarbon derivative / Organic salt / Organooxygen compound / Carbonyl group Molecular Framework Not Available External Descriptors Not Available ×Unlock Data

There is additional data available for commercial users including Adverse Effects, Contraindications, and Blackbox Warnings. Contact us to learn more about these and other features.

Learn more

Drug created on December 03, 2015 09:51 / Updated on February 02, 2020 02:27

Magnesium Citrate

Cathartic Agents

Three different cathartic agents have been used for CTC at UW. These include magnesium citrate, sodium phosphate, and polyethylene glycol (PEG). Each specific cathartic agent carries certain advantages and disadvantages. Small-volume osmotic cathartics (magnesium citrate and sodium phosphate) are easier to ingest but create relatively large fluid shifts in the individual, whereas large-volume osmotically balanced preparations (PEG) are much more difficult for the patient to complete but are generally safer for debilitated patients with tenuous fluid balances.

Magnesium citrate is a low-volume, osmotic cathartic agent. It has been in use as a bowel preparation agent for barium enema examinations since the 1960s. It is typically given in liquid form and has a fairly palatable taste. A standard dose is 300 mL (10 oz), which contains approximately 3 g of magnesium (Sunmark, San Francisco, CA). As opposed to the barium enema, in which a single dose is administered, a split, double-dose protocol is used at CTC (see later). Its cathartic action works primarily through the high osmolarity of the solution, which draws large amounts of fluid into the colonic lumen, creating a large effluent for catharsis. In addition, there is probable stimulation of fluid excretion by cholecystokinin release and activation of smooth muscle peristalsis to secondarily aid in clearing colonic material.7 The time of onset can be as early as 30 minutes, with a mean onset time of 2 hours from the administered dose. The duration of action may last up to 4 hours.8 When multiple doses are administered, the cleansing ability has been shown equivalent to other preparations at endoscopic evaluation.9,10 One of the recognized keys for efficacious cleansing is related to the individual’s hydration status. As is true of all cathartics that act through an osmotic nature to pull fluid into the colonic lumen, a well-hydrated state promotes cleansing activity, whereas a dehydrated status retards cathartic action, presumably as a result of a decreased effluent volume.7

One interesting observation from the barium enema era regarding magnesium citrate cathartic preparations may have an impact on CTC. It has been observed that magnesium interacts with barium suspensions in which there is increased barium coating of the colon. It is felt that residual magnesium cations within colonic mucus can associate with the negatively charged barium particles.11 For barium enema, this has resulted in alterations in protocol to decrease the propensity for excessive coating. For CTC, it emphasizes the importance of the use of diatrizoate within the preparation protocol (see later). Without the secondary cathartic effects of diatrizoate, right-sided adherent barium would presumably be increased with magnesium citrate–based preparations.

The advantages of magnesium citrate include a relatively small required volume administration and palatable taste, which both lead to improved patient compliance. The disadvantages are related to its osmotic nature, in which pulling fluid into the colon creates fluids shifts, ultimately from the intravascular space. Thus, this preparation should be avoided in patients with intolerance to changes in fluid balance related to significantly diminished renal or cardiac function. It should also be used with caution in patients eating a low-sodium diet. In general, a well-hydrated status prior to the bowel preparation is recommended to decrease risks of orthostasis. In addition, it is important to remember that the induced colonic catharsis will further affect the patient’s fluid status, thus requiring adequate oral fluid intake during this period to maintain a well-hydrated status. Holte and colleagues demonstrated a median weight loss of slightly more than 1 kg with use of an osmotic-based cathartic regimen despite a median fluid intake of close to 4 L over this time.12

Overall, magnesium citrate is felt to be a safe cathartic option that is well tolerated. Indeed, it has had a long track record of use at barium enema for several decades. In addition, the use of a double dose at CTC is likely very safe in the general population. Picosalax (sodium picosulphate with magnesium citrate) has been widely used in Europe as a cathartic agent since the early 1980s. This regimen administers the equivalent of a double dose of magnesium citrate (3.5 g of magnesium in each sachet; two sachets are given in total). Contraindications to magnesium citrate administration include patients with abdominal pain or hemorrhage, intestinal obstruction, and renal failure.13 Because the major route of excretion is through the urinary system, use of this agent should be avoided in patients with significant renal dysfunction because it could potentially lead to severe hypermagnesemia. Severe, even fatal, consequences have been reported with magnesium citrate use with patients with frank renal failure.14

In the UW program, magnesium citrate was initially used as the secondary cathartic option within the bowel preparation protocol, constituting approximately 10% of the patients. Magnesium citrate was reserved for patients with relative contraindications for administering sodium phosphate. Sodium phosphate had been favored over magnesium citrate because of its excellent cleansing properties with only a single 45-mL dose. Recently, we changed over to magnesium citrate as the primary cathartic option following the outcome of a direct comparison of efficacy between the two regimens in which equivalency was seen15 and because of the emerging concerns for acute phosphate nephropathy associated with sodium phosphate use (see later).

Sodium phosphate is a buffered saline osmotic cathartic containing both monobasic and dibasic forms. It is typically given in liquid form, although it is also available in tablets. Its cathartic action works through the high osmolarity of the solution, which draws large amounts of fluid into the colonic lumen with resultant large effluent and catharsis. The average time to onset of bowel activity is within 2 hours, although the response often occurs much sooner.16 It is highly effective in colonic cleansing and considered equivalent or superior to other cathartics such as PEG.17-19 As with other osmotic cathartics, the mechanism of action creates large fluid shifts within the individual, which may become problematic in people with limited cardiac or renal functioning. Traditionally, sodium phosphate for optical colonoscopy preparation has been administered in two 45-mL doses separated by 5 to 12 hours.20 We initially used a double-dose protocol for CTC1; however, a prospective comparison between single- and double-dose sodium phosphate demonstrated that the dose could be reduced to a single 45-mL administration at CTC with equivalent cleansing results.21 Such a reduction was possible as a result of the additional cathartic effects of the diatrizoate tagging agent given during CTC bowel preparation (see later).

The major advantage of sodium phosphate is related to its low-volume 45-mL administration. It is substantially lower than even the low-volume magnesium citrate–based regimen (two doses of 300 mL). Several studies have demonstrated increased compliance in completing the cathartic regimen compared to the 4-L large-volume PEG regimens.17 Disadvantages are primarily related to the lower safety margin. Sodium phosphate creates large fluid shifts in individuals and has demonstrated electrolyte changes including transient hyperphosphatemia and potential hypocalcemia. However, in the past, studies have shown an overall favorable safety profile in the typical healthy screening individual.17-20,22,23 Most adverse events were felt to be related to inappropriately administered, higher-than-recommended doses or given to inappropriate patient groups.20 Sodium phosphate use is contraindicated in patients with significant renal insufficiency and other conditions in which rapid fluid and electrolyte shifts are risky, such as congestive heart failure and cirrhosis.

In recent years, a rare but significant complication has been identified with sodium phosphate use.24,25 Small numbers of individuals with previously normal renal function subsequently developed renal failure following sodium phosphate use that was largely irreversible. This rare event (termed acute phosphate nephropathy) is currently poorly understood, but patients who have developed this condition following sodium phosphate administration have demonstrated worsening renal failure with histologic findings of acute/chronic tubular injury and abundant calcium phosphate deposition. Persons at risk include older individuals with a history of hypertension taking angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, or diuretic medications. Dehydration is felt to be a potential contributing factor.26

In our program, sodium phosphate had long stood as the main cathartic of choice, accounting for nearly 90% of our patients. It was very effective in colonic cleansing with a high compliance rate among patients because of the need for only a small volume for ingestion. In healthy, middle-aged adults of whom a typical screening population represents, it was felt to be a safe agent to administer; the safety margin was further increased by use of a single dose (as opposed to the standard split double-dose regimen for colonoscopy). Nonetheless, we shifted over to a magnesium citrate–based protocol to simplify the cathartic options from a programmatic standpoint and to address the emerging concerns regarding sodium phosphate use. Several months later, safety warnings were issued by the Food and Drug Administration, leading to the voluntary recall of all over-the-counter sodium phosphate products for bowel cleansing.

PEG is a third option for colonic cleansing. It is an osmotically balanced solution containing various electrolytes and a high molecular weight nonabsorbable polymer. This cathartic is nonabsorbable with negligible fluid and electrolyte shifts across the colonic mucosa. Because of the osmotic pressure created by the polymer, the electrolyte solution remains intraluminal and can then act as a colonic cleanser via lavage.27 Time to onset is typically 30 minutes to 1 hour. It is effective for cleansing the colon and has been in use for colonoscopy for many years but requires a large-volume administration of 4 L. The main advantage is the lack of appreciable fluid or electrolyte shifts as a result of its nonabsorbed nature. It does, however, lead to a large amount of residual colonic fluid (“a wet prep”), which is not ideal but not a major problem for CTC interpretation when tagging agents are administered to opacify the fluid. The major disadvantage revolves around patient compliance because complete ingestion of the solution is difficult because of its poor palatability and large volume. The 4-L administration translates into sixteen 8-ounce cups taken every 10 minutes. More recently, PEG preps consisting of 2-L administration have been introduced, which should improve patient compliance but may degrade the prep quality.

In our program, PEG is used infrequently, in less than 1% of patients. It is reserved for patients who are significantly debilitated and/or cannot tolerate any fluid shifts. Most patients enrolled in our screening program are typically fairly healthy outpatients, and low-volume osmotic cathartic preparations are more suitable for them.


Doc, I had to quit drinking that stuff, it was giving me diarrhea.

Pity the poor bowel prep researchers. Since colonoscopy was first introduced, they have undertaken the Herculean task of trying to design the means to vigorously and completely cleanse the colon in a way that is pleasant and tolerable for the patient. Over the same time, the expectations of endoscopists have increased: it is no longer adequate for the colon to merely be ‘clean’, it must be pristine. Any residual stool could hide a flat adenoma. The patients undergoing colonoscopy have also changed. Many are not patients at all, but instead, are healthy, asymptomatic individuals undergoing colonoscopy as a screening test for colorectal cancer. The bowel preparation is not only unpleasant, but it is frequently inconvenient, adding to the time lost from work or normal activities that results from undergoing a colonoscopy. Finally, a truly huge number of colonoscopies are performed each year (1). Even rare complications are of concern. Therefore, the bowel prep researcher seeks the perfect prep: one that immaculately cleanses the colon while being pleasant and convenient for the patient, and having an infinitesimally small risk of complications.

In the current issue of The Canadian Journal of Gastroenterology, two articles add to our knowledge in this area. Given the growing concern about missed neoplastic lesions in the right colon, the article by Kao et al (2) (pages 657–662) is timely. The authors report a randomized controlled trial of four bowel cleansing regimens: 4 L of polyethylene glycol (PEG) over a 4 h period; 2 L of PEG + bisacodyl; two 45 mL doses of sodium phosphate; and Pico-Salax (Ferring Pharmaceuticals Inc, Canada) plus 300 mL of magnesium citrate. A split-dose protocol, with some of the prep taken on the day of the colonoscopy, was used for those undergoing an afternoon colonoscopy. Although the authors do report a statistically significant difference between the bowel preps in the total score and the score for the right colon, it appears to be largely driven by the oral sodium phosphate preparation, which had the worst scores and is no longer on the market. The scores for the other three preps were quite similar, with a mean Ottawa Bowel Preparation Scale score for the right colon of 1.35, 1.10 and 1.37 for 4 L PEG, bisacodyl + 2 L PEG and Pico-Salax plus magnesium citrate, respectively (a score of 0 is excellent). The differences between the preparations only held true for colonoscopies performed in the morning, although, here again, the differences between the three commercially available preparations were small. However, the quality of the bowel preparations were generally better in the afternoon procedures compared with the morning procedures, and the scores for the right colon were consistently worse than those for the distal colon. Symptoms, including nausea, vomiting, abdominal cramps and bloating, were commonly reported for all bowel preparations.

The article by Vanner and Hookey (3) (pages 663–666) describes what the patient experiences after undergoing a sodium picosulphate/magnesium citrate and bisacodyl regimen. Patients frequently ask what to expect when they are taking the bowel prep. Can they do this? Can they go there? Beyond telling them that they are going to experience significant diarrhea that will last several hours, I am usually at a loss to give them more specifics (fortunately having no personal experience to draw on). The authors had 100 patients keep a diary of their bowel preparation experiences. Bisacodyl 10 mg was taken in the evening on the second and third days before the colonoscopy. Patients whose colonoscopy was scheduled for after 11:00 took one dose of Pico-Salax at 19:00 the evening before the colonoscopy and the second dose at 06:00 on the day of the colonoscopy. Patients who were scheduled before 11:00, took both doses the evening before at 17:00 and 22:00, respectively. The authors report that the first bowel movement occurred approximately 8 h to 9 h after each dose of bisacodyl, and the total number of bowel movements averaged approximately 3.5 per day. After the first dose of Pico-Salax, the average time to first bowel movement was 1.5 h, and patients experienced a mean of 4.4 bowel movements over the next 4 h. Patients taking the second dose of Pico-Salax at 22:00 had, on average, 6.5 bowel movements over the next 10 h. Those taking the second dose at 06:00 had, on average, 4.5 bowel movements over the next 4 h. Vanner and Hookey also found that the total number of bowel movements was positively associated with the quality of the bowel cleansing.

So, what lessons from these studies can I apply to my practice setting? The bulk of my time is spent in a community endoscopy centre that performs approximately 1000 colorectal cancer screening-related colonoscopies each month. As with any busy endoscopy unit, the quality of the bowel preparation is critically important. Preparations that are poorly tolerated or result in inadequate cleansing waste resources because they result in no-shows and cancelled appointments, procedures that need to be rescheduled and surveillance colonoscopies performed at shorter intervals than recommended by clinical practice guidelines. The primary message I take from the study by Kao et al (2) is that commercially available bowel preparations perform generally well, without marked differences with respect to the quality of colon cleansing. Even in terms of tolerability, they were quite similar, with only a 0.56 unit difference between the best and worst tolerated preps measured using a 7-point scale. It appears that all of the randomized patients were able to complete the bowel preparation and undergo their colonoscopy, with only four procedures being incomplete due to poor prep. Therefore, I do not see a clear winner in these results that would prompt me to change the current bowel preparation regimen (ie, split-dose PEG) at the Forzani & McPhail Colon Cancer Screening Centre (Calgary, Alberta).

For patients undergoing a Pico-Salax/bisacodyl regimen, I can now provide better information about what to expect: do not expect quick action after the bisacodyl; do not stray far from a bathroom for several hours after taking the Pico-Salax; and, if you are taking the Pico-Salax at 22:00, do not expect to get much sleep.

I’ve never used it, but found the following thru Google,; last sentance says 1/2 hour to six hours:
Magnesium Ccitrate
A magnesium salt of citric acid, is a chemical agent used medicinally as a saline laxative and to completely empty the bowel prior to a major surgery or colonoscopy. It is available without a prescription, both as a generic brand or under the brand name Citromag or Citroma. It is also used as a magnesium supplement in pills. The magnesium content of magnesium citrate corresponds to about 11% by mass.
Mechanism of action
Magnesium citrate works by attracting water through the tissues by a process known as osmosis. Once in the intestine, it can attract enough water into the intestine to induce defecation. The additional water helps to create more feces, which naturally stimulates bowel motility. This means it can also be used to treat rectal and colon problems. Magnesium citrate functions best on an empty stomach, and should always be followed with a full (eight ounce) glass of water or juice to help the magnesium citrate absorb properly and help prevent any complications. Magnesium citrate is generally not a harmful substance, but care should be taken by consulting a health-care professional if any adverse health problems are suspected or experienced.
Use and dosage
The maximum Upper Tolerable Limit for magnesium in supplement form for adults is 350 mg per day of elemental magnesium according to the National Institutes of Health (NIH). In addition, according to the NIH, total dietary requirements for magnesium from all sources (i.e. food and supplements) is 320–420 mg of elemental magnesium per day, though there is no UTL for dietary Magnesium. As a laxative syrup with a concentration of 1.745 g of magnesium citrate per fl. oz, a typical dose for adults and children twelve years or older is between 7 and 10 US fluid ounces (210 and 300 ml; 7.3 and 10 imp fl oz), followed immediately with a full 8 US fluid ounces (240 ml; 8.3 imp fl oz) glass of water. Consuming an adult dose of 10 oz of laxative syrup (@ 1.745 g/oz) implies a consumption of 17.45 g of magnesium citrate in a single 10 oz dose resulting in a consumption of approximately 2.0 g of elemental magnesium per single dose. Given that this laxative dose contains five times the recommended nutritional dose for magnesium, caution should be taken to avoid prolonged usage (i.e. over five days) and to follow the manufacturer’s instructions strictly. For children between three and twelve years of age, the typical dose is roughly half that, based on physician recommendation. Magnesium citrate is not recommended for use in children and infants two years of age or less.
Although less common, as a magnesium supplement the citrate form is sometimes used due to its increased bio-availability to other common pill forms, such as magnesium oxide. However, according to some studies magnesium gluconate may be more bio-available than magnesium citrate. Higher doses, up to 500 mg daily, have been used effectively in the prophylaxis of migraines, in combination with riboflavin (vitamin B2) 400 mg and, in some cases, a supplement of coenzyme Q10. Similar dosages apply when used as a supplement to help prevention of kidney stones.
Magnesium citrate, as a supplement in pill form, is useful for the prevention of kidney stones.
Side effects
It is always important to correctly follow the prescribed doses; extreme magnesium overdose can result in serious complication such as slow heart beat, low blood pressure, nausea, drowsiness, etc. If severe enough, an overdose can even result in coma or death. However, a moderate overdose will be excreted through the kidneys, unless one suffers from serious kidney problems.
Magnesium citrate solutions generally PRODUCES BOWEL MOVEMENT IN ONE HALF TO SIX HOURS. Rectal bleeding or failure to have a bowel movement after use could be signs of a serious condition.
HTH, Rick

What is Magnesium Citrate

A question I’m getting lately is, “What is Magnesium Citrate?”

I didn’t understand the influx of requests about this until I read the Facebook post that’s made its way around the ‘net. For full context, if you have not yet asked me, “What is magnesium citrate” and/or have not seen the post, you must first check it out HERE.

If Mr. Raposo wasn’t famous for his wise (and hilarious) words before, now he certainly is.

And here is why I feel as though I’m qualified to write this post…..I know exactly what he is talking about.

I’ve told the story to many people throughout my life and even told it to all of you recently again when I wrote Magnesium, Constipation, and Digestion,

Back before I started healing naturally (vs. with a random drugs and medications), on my worst days, my GI would have me drink an entire bottle of Magnesium Citrate. It didn’t matter which kind or which brand, so he’d tell me to “go to Walgreens and get this one.” Yes, an entire bottle of that nastiness.

These were for the most distended days. It was miserable, but it worked like a charm. At the time, I thought a bottle of Magnesium Citrate was my cure.

I would never drink that now.

Legit – I think I’ve done it a handful of times in my life.

So the answer is, “Yes. Yes it’s just as awful as he describes it.” Okay, maybe not as bad, but so close.

The question remains, “What is Magnesium Citrate?”

Click HERE to save this post for later.

In both his image and the one I linked to, it technically says, “Magnesium Citrate. Saline Laxative Oral Solution.” The one I took was not dye free; his at least was. But let’s break down the ingredients contained in either/both.

Magnesium Citrate – 1.745 g (Saline Laxative)

Magnesium citrate is the generic name for over-the-counter products such as Citroma or Citrate of Magnesia, which can be used as a laxative or dietary supplement. It belongs Magnesium citrate belongs to group of drugs known as saline laxatives, which work by pulling more water into the colon in order to help the colon empty its contents.

Magnesium Citrate should not be confused for magnesium, though, which I have also discussed as it relates to constipation.

While Magnesium Citrate is a type of magnesium (another type is magnesium sulfate, which is what Epsom salt is!), magnesium in general is more of a supplement; the Magnesium Citrate, a laxative.

The difference is the dose.

Citric Acid

Citric Acid is naturally found in citrus fruits, but it can also be manufactured as an additive in food, cleaning agents, and nutritional supplements. When used in a bottle of Magnesium Citrate, it is obviously manufactured.

Citric Acid is one of the most common food additives in the world and it’s used to boost acidity, enhance flavor, and preserve ingredients.

It is generally regarded as safe, but as with any additive, some people can have a reaction to it. (Note: namely those with mold sensitivities, as discussed HERE.)


Flavors is one of the most ambiguous terms in food and product labeling. You might see it called flavors or natural flavoring.

You literally will have no clue what that means because there are thousands of combinations it could be. (This is a fact. One of the food companies I worked for in the past had a world-renowned food scientist on the team. I learned that from her.)

Purified Water

Lovely! This laxative uses water that has been filtered or processed to remove impurities like chemicals and other contaminants.

Purified water is a good thing.

Red 40

Red 40 was present in the bottle of Magnesium Citrate I used to always drink.

The U.K. has already figured this one out. They have banned it, and for good reason. It has been linked to cancer, childhood spectrum disorders, stomach issues and more.

If you want to watch a super short clip on Red 40, read Tricked by Red JELLO.

Saccharin Sodium

Saccharin is on my list of 192 Sugar Sources and Alternate Names.

It’s a non-nutritive (artificial) sweetener that’s 300-400 times sweeter than regular sugar. It’s used as both a sweetener and preservative.

Some sources say it’s perfectly fine for consumption, but organizations like the NIH have found health risks from consuming it.

Sodium Bicarbonate

Sodium Bicarbonate = NaHCO₃ = baking soda.

It is used to relieve heartburn, sour stomach, or acid indigestion by neutralizing excess stomach acid.

Magnesium Citrate Warnings

In case you absolutely must take it, here are the warnings (written right on the bottle):

Ask a doctor before use if you have:

  • Kidney disease
  • A magnesium restricted diet
  • A sodium restricted diet
  • Stomach pain, nausea or vomiting
  • Noticed a sudden change in bowel habits that lasts more than 1 week

Alternatives to Magnesium Citrate

If constipation is your issue, there are alternatives. And if you want to see an entire list of them, grab 15 Ways to Deal with Constipation.

However, if you’re taking it because it’s part of a Colonoscopy prep, do not substitute anything. It’s imperative that you follow the doctor’s orders prior to the procedure or they might not be able to perform it on your scheduled day.

Final Thoughts on Magnesium Citrate

Do I think you’ll die if you drink a bottle of this powerful laxative? Absolutely not. I didn’t. You won’t.

What’s important here are these 3 things:

  1. Mr. Raposo’s account of what happens is pretty accurate. It’s no picnic drinking a bottle of Magnesium Citrate.
  2. Looking back, knowing what I know now, I would have never simply settled for just drinking a bottle of Magnesium Citrate when the GI doctor told me that was “all I needed” in order to make the severe stomach distention go away. In most cases, Magnesium Citrate is just the mask.
  3. If you must drink it (for Colonoscopy prep), grab the dye free one. You definitely don’t need the Red 40.



You will heal. I will help.

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