From Web MD:

Magnesium Sulfate - Uses, Side Effects, and More

COMMON BRAND(S): URO-MAG

GENERIC NAME(S): MAGNESIUM SULFATE

• Uses
• Side Effects
• Precautions
• Interactions
• Overdose
• Images
• Reviews (0)

Uses

This medication is a mineral supplement used to prevent and treat low amounts of magnesium in the blood. Some brands are also used to treat symptoms of too much stomach acid such as stomach upset, heartburn, and acid indigestion. Magnesium is very important for the normal functioning of cells, nerves, muscles, bones, and the heart. Usually, a well-balanced diet provides normal blood levels of magnesium. However, certain situations cause your body to lose magnesium faster than you can replace it from your diet. These situations include treatment with "water pills" (diuretics such as furosemide, hydrochlorothiazide), a poor diet, alcoholism, or other medical conditions (such as severe diarrhea/vomiting, stomach/intestinal absorption problems, poorly controlled diabetes).

How to use Magnesium Sulfate

Take this product by mouth as directed. Follow all directions on the product package. If you have any questions, ask your doctor or pharmacist.

It is best to take magnesium supplements with a meal to reduce stomach upset and diarrhea unless otherwise directed by the product instructions or your doctor.

Take each dose with a full glass (8 ounces or 240 milliliters) of water unless your doctor directs you otherwise. Swallow extended-release capsules and delayed-release/enteric coated tablets or capsules whole. Do not crush or chew extended-release or delayed-release/enteric coated capsules or tablets. Doing so can release all of the drug at once, increasing the risk of side effects. Also, do not split extended-release tablets unless they have a score line and your doctor or pharmacist tells you to do so. Swallow the whole or split tablet without crushing or chewing.

If you are taking the chewable tablets, chew each tablet thoroughly before swallowing.

If you are using a liquid product, use a medication measuring device to carefully measure the dose. Do not use a household spoon because you may not get the correct dose. If you are using a suspension, shake the bottle well before each dose.

Take this medication regularly in order to get the most benefit from it. Remember to take it at the same time(s) each day. Dosage is based on your medical condition and response to treatment. Do not increase your dose or take it more often than directed on the product package or by your doctor. Too much magnesium in the blood can cause serious side effects.

Tell your doctor if symptoms of low magnesium blood levels (such as muscle cramps, tiredness, irritability, depression) last or get worse. If you think you may have a serious medical problem, get medical help right away.

Precautions

Before taking a magnesium supplement, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

If you have the following health problem, consult your doctor or pharmacist before using this product: kidney disease.

Liquids, powders, or some other forms of this product may contain sugar and/or aspartame. Liquid products may also contain alcohol. Caution is advised if you have diabetes, alcohol dependence, liver disease, phenylketonuria (PKU), or any other condition that requires you to limit/avoid these substances in your diet. Ask your doctor or pharmacist about using this product safely.

During pregnancy, this product should be used only when clearly needed. Discuss the risks and benefits with your doctor.

Interactions

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug are: cellulose sodium phosphate, digoxin, sodium polystyrene sulfonate.

Magnesium can bind with certain medications, preventing their full absorption. If you are taking a tetracycline-type medication (such as demeclocycline, doxycycline, minocycline, tetracycline), separate the time of the dose from the time of the magnesium supplement dose by at least 2 to 3 hours. If you are taking a bisphosphonate (for example, alendronate), a thyroid medication (for example, levothyroxine), or a quinolone-type antibiotic (such as ciprofloxacin, levofloxacin), ask your doctor or pharmacist about how long you should wait between doses and for help finding a dosing schedule that will work with all your medications.

Check the labels on all your prescription and nonprescription/herbal products (such as antacids, laxatives, vitamins) because they may contain magnesium. Ask your pharmacist about using those products safely.

Does Magnesium Sulfate interact with other drugs you are taking?

Overdose

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include slow heartbeat, severe drowsiness, dizziness, confusion, muscle weakness, loss of consciousness.

Notes

Lab and/or medical tests (such as magnesium blood levels, kidney function) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

Magnesium supplements are available in different forms with different amounts of magnesium. Many are available without a prescription. Ask your doctor or pharmacist for help in selecting the best product for you.

Eat a well-balanced diet. Foods high in magnesium include avocados, bananas, beans, whole grain cereals, green vegetables, and nuts.

Missed Dose

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

From NIH, National Library of Medicine

um Sulfate

Matthew A. Hicks; Alka Tyagi.

Author Information and Affiliations

Last Update: May 1, 2023.

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Continuing Education Activity

Magnesium sulfate is a medication used to manage and treat multiple clinical conditions and holds several on and off-label uses. This activity outlines the indications, mechanism of action, and contraindications for magnesium sulfate as a valuable agent in treating magnesium electrolyte abnormalities, eclampsia, and constipation.

Objectives:

• Describe the metabolism of magnesium and how it is absorbed and excreted to maintain therapeutic levels.
• Review the clinical symptoms seen in hypo- and hypermagnesemia.
• Identify the potential adverse effects of magnesium sulfate administration.
• Explain the importance of proper magnesium sulfate administration and the need to be aware of the on and off-label uses and current magnesium levels to ensure appropriate dosing occurs.

Access free multiple choice questions on this topic.

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Indications

Magnesium sulfate is a common medication in the hospital setting with a variety of uses. It currently holds many FDA approvals but also has numerous off-label uses for a variety of clinical situations.

FDA-approved Indications [1] [2]

• Constipation
• Hypomagnesemia
• Prevention of seizures in eclampsia/preeclampsia
• Acute nephritis (pediatric patients)
• Cardiac arrhythmias secondary to hypomagnesemia
• Soaking minor cuts or bruises

Non-FDA-approved Indications [3] [4]

• Acute asthma exacerbations
• Torsades de pointes during ACLS
• Tocolytic to prevent preterm labor
• Sleep: up to 400 mg at bedtime

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Mechanism of Action

Magnesium Metabolism

To fully understand how magnesium sulfate works clinically, a basic understanding of how magnesium works intracellularly is helpful. Magnesium is a positively charged divalent cation that is absorbed in the gastrointestinal tract from our diets. Regulation of magnesium concentration in the serum occurs mostly through renal reabsorption and excretion. Parathyroid hormone causes magnesium reabsorption in the cortical thick ascending limb, but hypercalcemia and hypermagnesemia will cause magnesium excretion. Serum magnesium levels should remain within a range of 0.7 to 1 mmol/L (1.4 to  2.0 meq/L) concentration, but almost half of the total body magnesium is taken up by the bone.[5]

Physiological Role of Magnesium

One role that magnesium plays is helping ion transport and maintain balance across the cellular membrane. Magnesium also acts as cofactors for enzymatic activation in multiple biochemical pathways such as glycolysis and the Krebs cycle. Intracellular magnesium is vital for neurochemical transmission and muscular contractions by working indirectly at the neuromuscular junction. More specifically, Mg2+ ions compete on voltage-gated calcium channels, affecting the distribution of calcium uptake and release. Magnesium also affects calcium metabolism by stimulation or suppression of Parathyroid Hormone (PTH).

Hypermagnesemia

Hypermagnesemia is a state of elevated magnesium levels with serum concentrations higher than 2 mmol/L. It rarely presents unless renal insufficiency is present or the patient is exposed to high levels of exogenous magnesium. Clinical signs of hypermagnesemia result in neuromuscular blockade or vasodilation—high levels of circulating magnesium lead to inhibition of calcium influx through the voltage-gated channels. Without calcium influx into the cell at the neuromuscular junction, no acetylcholine is released, leading to muscle contraction slowing. Clinical symptoms of hypermagnesemia include, but are not limited to, weakness, decreased respiratory drive, hyporeflexia, hypotension, or electrocardiogram (ECG) changes. The most notable ECG changes are P-R interval prolongation, an increase in the Q-T interval, or an increase in QRS duration leading to heart block.

Hypomagnesemia

Usually defined as depletion of magnesium and is seen when serum concentrations are less than 0.7 mmol/L. Typically due to intestinal malabsorption or renal disease leading to failed reabsorption. Low levels of magnesium can result in the loss of competitive inhibition at the neuromuscular junction, allowing for increased acetylcholine release, resulting in neuromuscular irritability. Without competitive inhibition, the threshold of motor nerve excitation diminished, leading to enhanced myofiber contraction. Clinical symptoms of hypomagnesemia include, but are not limited to, muscle spasms, hyperreflexia, or ECG changes. Most notable changes seen on ECG include the widening of the P-R interval, widening of the QRS complex, and peaking of the T waves.[6]

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Administration

Magnesium sulfate can administration can be oral (PO), intramuscular (IM), intraosseous (IO), or intravenous (IV). For every 1 gram of magnesium sulfate, it contains 98.6 mg or 8.12Eq of elemental magnesium. Magnesium sulfate can be combined with dextrose 5% or water to make intravenous solutions.

• Oral: Magnesium sulfate is available as a capsule or powder (Epsom salt), which can be combined with water to form an oral solution.
• Intramuscular: If diluted, magnesium sulfate can be administered IM in children and adults.
• Intraosseous: Magnesium sulfate can be administered through an adequately placed IO if no other access is available.
• Intravenous: Magnesium sulfate can be administered as an IV push, infusion, or additive to TPN.

Magnesium given orally leads to osmotic shifts of fluid, which can help alleviate constipation. If given parenterally, magnesium sulfate will be broken down into elemental magnesium and used to replete and maintain circulating magnesium stores, thus changing the serum concentration of magnesium. When given to patients, the route of administration will ultimately determine the overall mechanism of action.

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Adverse Effects

When giving magnesium sulfate, there are minimal side effects with standard therapeutic doses, but magnesium sulfate has a broad therapeutic index. Patients most commonly complain of minor facial flushing and warmth with the administration; however, symptoms typically resolve spontaneously. In patients with neuromuscular disease, such as in myasthenia gravis, the neuromuscular function may worsen at lower concentrations of medication. If given rapidly or in high doses, patients may experience transient hypotension due to smooth muscle inhibition causing a vasodilatory effect that will resolve. If the patient is on a continuous magnesium sulfate infusion, serum levels must be accounted for as symptoms related to hypermagnesemia may become clinically evident. At supratherapeutic serum concentrations, absent reflexes, abnormal cardiac conduction, and muscle weakness may occur.

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Contraindications

If any known hypersensitivity reaction to magnesium sulfate has occurred in the past, it should not be administered. If a patient is in a known heart block, magnesium sulfate should not be given as it can exacerbate the already slowed cardiac conduction. Many manufacturing labels recommend withholding magnesium sulfate infusions in patients with preeclampsia/eclampsia two hours before fetal delivery due to possible interaction with neuromuscular blocking agents given intraoperatively; however, the medication should not be stopped due to the possibility of precipitating seizure activity.[7]

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Monitoring

Magnesium levels must be monitored frequently by checking serum levels every 6 to 8 hours or clinically by checking patellar reflexes or urinary output.  If serum concentration levels are low, a proper dose of magnesium sulfate can be given parenterally to replete low serum concentrations with recommended follow-up laboratory testing.

• Normal Serum Levels: 0.7 to 1.0 mmol/L (1.4 to 2.0 meq/L)
• Therapeutic level in preeclampsia/eclampsia: 2.0 to 3.5 mmol/L (4 to 7 meq/L)
• Patellar reflexes lost: 4.0 to 5.0 mmol/L (8 to 10 meq/L)
• Respiratory depression: 5.0 to 7.5 mmol/L (10 to 15 meq/L)
• Respiratory paralysis: 6.0 to 7.5 mmol/L (12 to 15 meq/L)
• Cardiac arrest: 12.5 to 15.0 mmol/L (25 to 30 meq/L)

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Toxicity

If patients exhibit signs and symptoms of hypermagnesemia, the recommendation is to discontinue magnesium sulfate products immediately. If the patient consumed magnesium sulfate orally, then the use of magnesium-free enemas or cathartics can be useful in removing excess magnesium from the GI tract. Patients should receive parenteral doses of calcium gluconate to help alleviate symptoms, but continued doses may be necessary as the calcium provides temporary improvement. IV hydration should also occur if clinically appropriate. In patients with severe renal disease, then hemodialysis should be considered.

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Enhancing Healthcare Team Outcomes

Magnesium sulfate is a very commonly used medication in the hospital setting with multiple therapeutic uses. Interprofessional healthcare team members, including clinicians, physician assistants, nurse practitioners, and pharmacists who prescribe or dispense this medication, should be aware of the on and off-label uses and current magnesium levels to ensure appropriate dosing occurs. The pharmacist should help monitor for potential drug-drug interactions, and nursing staff needs to be fully aware of the proper administration of the medications. All individuals taking care of the patient should be mindful of potential side effects from magnesium sulfate administration and how to manage complications. Interprofessional coordination will optimize therapeutic outcomes when using this agent while minimizing adverse events. [Level 5]