What obstetric conditions is magnesium sulfate used for?

Table of Contents Show

What Are Side Effects Associated with Using Magnesium Sulfate?
What Other Drugs Interact with Magnesium Sulfate?
For the Baby

ACOG and SMFM continue to support the short-term (usually less than 48 hours) use of magnesium sulfate in obstetric care for prevention and treatment of seizures in women with preeclampsia or eclampsia, fetal neuroprotection, and short-term tocolysis to allow for the administration of antenatal corticosteroids.

The FDA has changed the drug classification of magnesium sulfate from Category A to D. Change secondary to concern for fetal and neonatal bone demineralization and fractures associated with long-term in utero exposure to magnesium sulfate.

-18 cases in the Adverse Event Reporting System database that report fetal and neonatal long bone demineralization and fractures. -The average duration of prenatal magnesium sulfate exposure was 9.6 weeks, with an average total maternal dose of 3,700 g, a much longer duration and much higher dose than is currently recommended for obstetric use.

-These studies have important limitations in design: sample sizes in available population studies were generally small, making the conclusions of these studies subject to confounding and bias.

Magnesium sulfate has been used in obstetrics for decades, without any reports or concerns regarding fetal and neonatal demineralization.

-The uses of magnesium sulfate in the context of appropriate clinical obstetric practice include: -Prevention and treatment of seizures in women with preeclampsia or eclampsia. -Fetal neuroprotection before anticipated early preterm (less than 32 weeks of gestation) delivery. -Short-term prolongation of pregnancy (up to 48 hours) to allow for the administration of antenatal corticosteroids.

-Tocolysis is not recommended beyond 34 weeks of gestation, and it is generally not recommended before 24 weeks of gestation but may be considered based on individual circumstances at 23 weeks of gestation.

Practitioners should not stop using magnesium sulfate for these indications based on the FDA reclassification. In all of these conditions, prolonged use of magnesium sulfate is never indicated.

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KindProtein groupOrganismHumansPharmacological action

Yes

Actions

Inhibitor

Blocker

The magnesium regulates the channel gating by binding to the EF-hand motif region in the COOH-terminal tail of the α-subunit of the channel.

General FunctionVoltage-gated calcium channel activitySpecific FunctionVoltage-sensitive calcium channels (VSCC) mediate the entry of calcium ions into excitable cells and are also involved in a variety of calcium-dependent processes, including muscle contraction, hor...

Brunet S, Scheuer T, Klevit R, Catterall WA: Modulation of CaV1.2 channels by Mg2+ acting at an EF-hand motif in the COOH-terminal domain. J Gen Physiol. 2005 Oct;126(4):311-23. doi: 10.1085/jgp.200509333. Epub 2005 Sep 12. [Article]
Bara M, Guiet-Bara A: Magnesium regulation of Ca2+ channels in smooth muscle and endothelial cells of human allantochorial placental vessels. Magnes Res. 2001 Mar;14(1-2):11-8. [Article]
Kuo CC, Hess P: Block of the L-type Ca2+ channel pore by external and internal Mg2+ in rat phaeochromocytoma cells. J Physiol. 1993 Jul;466:683-706. [Article]
Zhao M, Feng R, Shao D, Liu S, Lei M, Wang H, Sun X, Guo F, Hu H, Kameyama M, Hao L: Mg(2+)-dependent facilitation and inactivation of L-type Ca(2+) channels in guinea pig ventricular myocytes. J Pharmacol Sci. 2015 Nov;129(3):143-9. doi: 10.1016/j.jphs.2015.08.001. Epub 2015 Aug 7. [Article]
Lin CY, Tsai PS, Hung YC, Huang CJ: L-type calcium channels are involved in mediating the anti-inflammatory effects of magnesium sulphate. Br J Anaesth. 2010 Jan;104(1):44-51. doi: 10.1093/bja/aep336. [Article]

What Are Side Effects Associated with Using Magnesium Sulfate?

Side effects associated with the use of Magnesium Sulfate, include the following:

Circulatory collapse
Respiratory paralysis
Low core body temperature (hypothermia)
Excess fluid in the lungs (pulmonary edema)
Depressed/poor reflexes
Low blood pressure (hypotension)
Flushing
Drowsiness
Depressed cardiac function/heart disturbances
Increased sweating
Low blood calcium (hypocalcemia)
Low blood phosphates (hypophosphatemia)
Low blood potassium (hyperkalemia)
Visual changes
Breathing difficulties
Confusion
Weakness
Flushing (warmth, redness, or tingly feeling)
Feeling like you might pass out
Anxiety
Cold feeling
Extreme drowsiness
Muscle tightness or contraction
Headache

This document does not contain all possible common side effects and other side effects that may occur. Check with your physician for additional information about the side effects of this drug.

What Other Drugs Interact with Magnesium Sulfate?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

Magnesium sulfate has no known severe interactions with other drugs.

Serious interactions of magnesium sulfate include:

Magnesium sulfate has moderate interactions with at least 24 different drugs.

Magnesium sulfate has mild interactions with at least 43 different drugs.

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more health information about this medicine.

[Effect of magnesium sulphate on mortality and neurologic morbidity of the very-preterm newborn (of less than 33 weeks) with two-year neurological outcome: results of the prospective PREMAG trial].

Marret S, Marpeau L, Follet-Bouhamed C, Cambonie G, Astruc D, Delaporte B, Bruel H, Guillois B, Pinquier D, Zupan-Simunek V, Bénichou J; le groupe PREMAG. Marret S, et al. Gynecol Obstet Fertil. 2008 Mar;36(3):278-88. doi: 10.1016/j.gyobfe.2008.01.012. Epub 2008 Mar 11. Gynecol Obstet Fertil. 2008. PMID: 18337147 Clinical Trial. French.

About half of the women who receive magnesium sulfate have some side effects. Potential side effects include flushing, feeling uncomfortably warm, headache, dry mouth, nausea, and blurred vision. Women often say they feel wiped out, as though they have the flu. These side effects can be uncomfortable, but they are not dangerous.

When given in high doses, magnesium sulfate can cause cardiac arrest and respiratory failure. Fortunately, women can be monitored for increases in the magnesium blood levels. If the levels become too high, the dose can be lowered.

One of the most common signs that nurses watch for is the loss of the knee-jerk reflex (a jerk that usually occurs when your leg is tapped just below the knee). Your urine output will also probably be measured every hour in the hospital to avoid toxicity.

If for some reason the levels get too high, another medication, called calcium gluconate, can help reverse the effects of magnesium sulfate.

For the Baby

Since magnesium sulfate relaxes most muscles, babies who have been exposed to magnesium for an extended period of time may be listless or floppy at birth. This effect typically goes away as the drug clears from the baby’s system.