Citrate of Magnesia

Magnesium is a naturally occurring mineral that is important for many systems in the body, especially the muscles and nerves. Magnesium citrate also increases water in the intestines.

Magnesium citrate is used as a laxative to treat occasional constipation.

Magnesium citrate may also be used for purposes not listed in this medication guide.

Ask a doctor or pharmacist if it is safe for you to take this medicine if you have other medical conditions, especially:

• kidney disease;

• a sudden change in bowel habits that has lasted longer than 2 weeks;

• stomach pain, nausea, vomiting; or

• if you are on a low-magnesium or low-potassium diet.

It is not known whether magnesium citrate will harm an unborn baby. Do not use this medicine without a doctor's advice if you are pregnant.

It is not known whether magnesium citrate passes into breast milk or if it could harm a nursing baby. Do not use this medicine without a doctor's advice if you are breast-feeding a baby.

Since magnesium citrate is used when needed, you may not be on a dosing schedule. If you are on a schedule, use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using magnesium citrate and call your doctor at once if you have:

• no bowel movement within 6 hours after taking the medicine;

• pain with bowel movements, rectal bleeding;

• watery diarrhea, nausea, vomiting, severe stomach pain;

• painful or difficult urination;

• flushing (warmth, redness, or tingly feeling);

• a light-headed feeling, like you might pass out;

• weak or shallow breathing, slow heartbeats; or

• muscle weakness, increased thirst.

Common side effects may include:

• loose stools, diarrhea, stomach cramps;

• upset stomach;

• dizziness; or

• increased sweating.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Applies to magnesium citrate: oral capsule, oral tablet

Other dosage forms:

• oral solution

Applies to magnesium citrate: compounding powder, oral capsule, oral liquid, oral tablet

Other

Mild hypermagnesemia is generally well-tolerated. Moderate or severe hypermagnesemia affects the nervous and cardiovascular systems primarily.[Ref]

Nervous system

Nervous system side effects have included a decrease in tendon reflexes, muscle weakness, mental confusion, sedation, mental depression, areflexia, coma and respiratory paralysis. CNS depression, often presenting as somnolence, may be more likely and more severe in patients with renal dysfunction.[Ref]

Nervous system side effects from hypermagnesemia result from suppression of neuromuscular transmission in the CNS and at the neuromuscular junction (which can be antagonized by calcium). Clinically, if serum magnesium (Mg) levels increase to 4 to 7 mEq/L, there may be a decrease in tendon reflexes, muscle weakness, and/or mental confusion or sedation. At levels of 5 to 10 mEq/L, the respiratory rate slows and blood pressure falls. At levels of 10 to 15 mEq/L, there is usually profound mental depression, areflexia, coma and respiratory paralysis. Mg also has a curare-like effect at the neuromuscular junction at serum levels above 10 mEq/L. Death is not uncommon when serum Mg levels rise to 15 mEq/L.[Ref]

Cardiovascular

The cardiovascular consequences of hypermagnesemia are due to peripheral vasodilation. Hypotension may be observed when serum Mg levels rise to 5 to 10 mEq/L. Hypotension, depressed myocardial conductivity, and bradyarrhythmias may be associated with levels greater than 10 mEq/L. While some patients are inexplicably able to tolerate extraordinarily high Mg levels, there is a significant risk of asystole when levels rise to 25 mEq/L. The risk of cardiotoxicity from hypermagnesemia is increased in the presence of hypocalcemia, hyperkalemia, acidosis, digitalis therapy, and renal insufficiency.[Ref]

Cardiovascular side effects have included hypotension, depressed myocardial conductivity, asystole, and bradyarrhythmias.[Ref]

Metabolic

A metabolic concern in the case of acute hypermagnesemia is hypocalcemia. Elevated Mg may cause hypocalcemia due to suppression of the release of parathyroid hormone (PTH) and competition for renal tubular reabsorption between calcium (Ca) and Mg. The latter can lead to decreased Ca reabsorption and hypercalciuria, which aggravates the hypocalcemia produced by decreased release of PTH.[Ref]

Metabolic side effects have included hypocalcemia. The effects of hypermagnesemia may be worsened by the presence of hypocalcemia, especially in patients with uremia.[Ref]

Gastrointestinal

Gastrointestinal side effects include nausea when serum Mg levels rise to 4 to 5 mEq/L.

Rare cases of paralytic ileus associated with serum Mg levels greater than 5 mEq/L have been reported.[Ref]

Gastrointestinal side effects have included nausea, and paralytic ileus (rarely).[Ref]

Some side effects of Citrate of Magnesia may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

< 6 years: 0.5 mL/kg orally up to a maximum of 200 mL. May repeat every 4 to 6 hours until stools are clear.

6 to 12 years: 100 to 150 mL orally one time.

Data not available

Summary of Use during Lactation

No information is available on the clinical use of magnesium citrate during breastfeeding. However, other magnesium salts have been studied. Intravenous magnesium sulfate increases milk magnesium concentrations only slightly. Oral absorption of magnesium by the infant is poor, so maternal magnesium citrate is not expected to affect the breastfed infant's serum magnesium. Magnesium citrate supplementation during pregnancy might delay the onset of lactation, but it can be taken during breastfeeding and no special precautions are required.

Drug Levels

Maternal Levels. Ten women with pre-eclampsia were given 4 grams of magnesium sulfate intravenously followed by 1 gram per hour until 24 hours after delivery. While the average serum magnesium was 35.5 mg/L in treated women compared to 18.2 mg/L in 5 untreated controls, colostrum magnesium levels at the time of discontinuation of the infusion was 64 mg/L in treated women and 48 mg/L in the controls. By 48 hours after discontinuation, colostrum magnesium levels were only slightly above control values and by 72 hours they were virtually identical to controls.[1]

Infant Levels. Relevant published information was not found as of the revision date.

Effects in Breastfed Infants

Fifty mothers who were in the first day postpartum received 15 mL of either mineral oil or an emulsion of mineral oil and another magnesium salt, magnesium hydroxide equivalent to 900 mg of magnesium hydroxide, although the exact number who received each product was not stated. Additional doses were given on subsequent days if needed. None of the breastfed infants were noted to have any markedly abnormal stools, but all of the infants also received supplemental feedings.[2]

Effects on Lactation and Breastmilk

One mother who received intravenous magnesium sulfate for 3 days for pregnancy-induced hypertension had lactogenesis II delayed until day 10 postpartum. No other specific cause was found for the delay, although a complete work-up was not done.[3] A subsequent controlled clinical trial found no evidence of delayed lactation in mothers who received intravenous magnesium sulfate therapy.[4] Some, but not all, studies have found a trend toward increased time to the first feeding or decreased sucking in infants of mothers treated with intravenous magnesium sulfate during labor because of placental transfer of magnesium to the fetus.[4][5]

A study in 40 pairs of matched healthy women with vaginally delivered singleton pregnancies, outcome endpoints were compared in those receiving continuous oral magnesium aspartate HCl supplementation mean dose of 459 mg daily (range 365 to 729 mg of magnesium daily) for at least 4 weeks before delivery versus non-supplemented controls. In the magnesium group, significantly fewer women could breastfeed their infants exclusively at discharge (63% vs 80%).[6]

Alternate Drugs to Consider

(Laxative) Bisacodyl, Docusate, Magnesium Hydroxide, Psyllium, Sodium Picosulfate, Sodium Phosphate

References

1. Cruikshank DP, Varner MW, Pitkin RM. Breast milk magnesium and calcium concentrations following magnesium sulfate treatment. Am J Obstet Gynecol. 1982;143:685-8. PMID: 7091241

2. Baldwin WF. Clinical study of senna administration to nursing mothers.:assessment of effects on infant bowel habits. Can Med Assoc J. 1963;89:566-7. PMID: 14045350

3. Haldeman W. Can magnesium sulfate therapy impact lactogenesis? J Hum Lact. 1993;9:249-52. PMID: 8260059

4. Riaz M, Porat R, Brodsky NL, Hurt H. The effects of maternal magnesium sulfate treatment on newborns: a prospective controlled study. J Perinatol. 1998;18:449-54. PMID: 9848759

5. Rasch DK, Huber PA, Richardson CJ et al. Neurobehavioral effects of neonatal hypermagnesemia. J Pediatr. 1982;100:272-6. PMID: 7199083

6. Meier B, Huch R, Zimmermann R et al. Does continuing oral magnesium supplementation until delivery affect labor and puerperium outcome? Eur J Obstet Gynecol Reprod Biol. 2005;123:157-61. PMID: 15899543