Magnesium Sulfate

INDICATIONS & USAGE Magnesium Sulfate Injection, USP is suitable for replacement therapy in magnesium deficiency, especially in acute hypomagnesemia accompanied by signs of tetany similar to those observed in hypocalcemia. In such cases, the serum magnesium level is usually below the lower limit of normal (1.5 to 2.5 mEq/L) and the serum calcium level is normal (4.3 to 5.3 mEq/L) or elevated. In total parenteral nutrition (TPN), magnesium sulfate may be added to the nutrient admixture to correct or prevent hypomagnesemia which can arise during the course of therapy. Magnesium sulfate injection is also indicated for the prevention and control of seizures in a pre-eclampsia and eclampsia, respectively.

DOSAGE & ADMINISTRATION Dosage of magnesium sulfate must be carefully adjusted according to individual requirements and response, and administration of the drug should be discontinued as soon as the desired effect is obtained. Both IV and IM administration are appropriate. IM administration of the undiluted 50% solution results in therapeutic plasma levels in 60 minutes, whereas IV doses will provide a therapeutic level almost immediately. The rate of IV injection should generally not exceed 150 mg/minute (1.5 mL of a 10% concentration or its equivalent), except in severe eclampsia with seizures (see below). Continuous maternal administration of magnesium sulfate injection in pregnancy beyond 5 to 7 days can cause fetal abnormalities. Solutions for IV infusion must be diluted to a concentration of 20% or less prior to administration. The diluents commonly used are 5% Dextrose Injection, USP and 0.9% Sodium Chloride Injection, USP. Deep IM injection of the undiluted (50%) solution is appropriate for adults, but the solution should be diluted to a 20% or less concentration prior to such injection in children. In Magnesium Deficiency In the treatment of mild magnesium deficiency, the usual adult dose is 1 g, equivalent to 8.12 mEq of magnesium (2 mL of the 50% solution) injected IM every six hours for four doses (equivalent to a total of 32.5 mEq of magnesium per 24 hours). For severe hypomagnesemia, as much as 250 mg (approximately 2 mEq) per kg of body weight (0.5 mL of the 50% solution) may be given IM within a period of four hours if necessary. Alternatively, 5 g (approximately 40 mEq) can be added to one liter of 5% Dextrose Injection, USP or 0.9% Sodium Chloride Injection, USP for slow IV infusion over a three-hour period. In the treatment of deficiency states, caution must be observed to prevent exceeding the renal excretory capacity. In Hyperalimentation In TPN, maintenance requirements for magnesium are not precisely known. The maintenance dose used in adults ranges from 8 to 24 mEq (1 to 3 g) daily; for infants, the range is 2 to 10 mEq (0.25 to 1.25 g) daily. In Pre-eclampsia or Eclampsia In severe pre-eclampsia or eclampsia, the total initial dose is 10 to 14 g of magnesium sulfate. Intravenously, a dose of 4 to 5 g in 250 mL of 5% Dextrose Injection, USP or 0.9% Sodium Chloride Injection, USP may be infused. Simultaneously, IM doses of up to 10 g (5 g or 10 mL of the undiluted 50% solution in each buttock) are given. Alternatively, the initial IV dose of 4 g may be given by diluting the 50% solution to a 10 or 20% concentration; the diluted fluid (40 mL of a 10% solution or 20 mL of a 20% solution) may then be injected IV over a period of three to four minutes. Subsequently, 4 to 5 g (8 to 10 mL of the 50% solution) are injected IM into alternate buttocks every four hours as needed, depending on the continuing presence of the patellar reflex and adequate respiratory function. Alternatively, after the initial IV dose, some clinicians administer 1 to 2 g/hour by constant IV infusion. Therapy should continue until paroxysms cease. A serum magnesium level of 6 mg/100 mL is considered optimal for control of seizures. A total daily (24 hr) dose of 30 to 40 g should not be exceeded. In the presence of severe renal insufficiency, the maximum dosage of magnesium sulfate is 20 grams/48 hours and frequent serum magnesium concentrations must be obtained. Continuous use of magnesium sulfate in pregnancy beyond 5 to 7 days can cause fetal abnormalities. Other uses In counteracting the muscle-stimulating effects of barium poisoning, the usual dose of magnesium sulfate is 1 to 2 g given IV. For controlling seizures associated with epilepsy, glomerulonephritis or hypothyroidism, the usual adult dose is 1 g administered IM or IV. In paroxysmal atrial tachycardia, magnesium should be used only if simpler measures have failed and there is no evidence of myocardial damage. The usual dose is 3 to 4 g (30 to 40 mL of a 10% solution) administered IV over 30 seconds with extreme caution. For reduction of cerebral edema, 2.5 g (25 mL of a 10% solution) is given IV. Incompatibilities Magnesium sulfate in solution may result in a precipitate formation when mixed with solutions containing: The potential incompatibility will often be influenced by the changes in the concentration of reactants and the pH of the solutions. It has been reported that magnesium may reduce the antibiotic activity of streptomycin, tetracycline and tobramycin when given together. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. DOSAGE and ADMINISTRATION

WARNINGS AND PRECAUTIONS • Fetal-neonatal toxicity with prolonged use : Administration beyond 5 to 7 days is not recommended and can lead to hypocalcemia and bone abnormalities ( 2.2 , 5.1 ) • Risk of magnesium toxicity : Monitor magnesium concentrations and clinical signs of magnesium toxicity including respiratory depression, an injectable calcium salt should be immediately available to counteract hazards, for significant toxicity stop Magnesium Sulfate in 5% Dextrose Injection ( 5.2 ) • Risk of elevated blood glucose: Solutions containing dextrose should be used with caution in patients with known prediabetes or diabetes mellitus ( 5.3 ) • Co-administration with unapproved tocolytics : Do not use concomitantly with beta adrenergic agents such as terbutaline and calcium channel blockers such as nifedipine ( 5.4 ) • Aluminum toxicity : Aluminum may reach toxic concentrations with prolonged parenteral administration in patients with renal impairment ( 5.5 ) • Exacerbation of Myasthenia Gravis : Use is contraindicated because use in patients with underlying myasthenia gravis can precipitate a myasthenic crisis ( 5.6 ) 5.1 Fetal-Neonatal Toxicity with Prolonged Use Continuous administration of magnesium sulfate beyond 5 to 7 days in pregnant women can lead to hypocalcemia and bone abnormalities in the developing fetus, including skeletal demineralization and osteopenia. In addition, cases of neonatal fracture have been reported. Neonates of women receiving Magnesium Sulfate in 5% Dextrose Injection (especially with prolonged maternal use) are at risk for magnesium toxicity including hyporeflexia, hypotonia, and respiratory depression. There is one reported case of neonatal death as the result of magnesium toxicity after transplacental exposure. The shortest duration of magnesium sulfate treatment that can lead to fetal harm is not known. Administration of Magnesium Sulfate in 5% Dextrose Injection beyond 5 to 7 days is not recommended. 5.2 Risk of Magnesium Toxicity Patients receiving Magnesium Sulfate in 5% Dextrose Injection are at risk for magnesium toxicity including respiratory depression, acute renal failure and rarely, pulmonary edema. Monitor clinical signs of magnesium toxicity (for example, facial edema, diminished strength of deep tendon reflexes, respiratory depression) and magnesium concentrations during infusions of Magnesium Sulfate in 5% Dextrose Injection. Clinical indications of a safe dosage regimen include the presence of the patellar reflex (knee jerk) and absence of respiratory depression (approximately 16 breaths or more per minute). Serum magnesium concentrations usually sufficient to control convulsions range from 3 to 6 mg per 100 mL (2.5 to 5 mEq per liter). The strength of the deep tendon reflexes begins to diminish when serum magnesium concentrations exceed 4 mEq per liter. Reflexes may be absent at concentration of 10 mEq per liter, at which point respiratory paralysis is a potential hazard. An injectable calcium salt should be immediately available to counteract the potential hazards of magnesium toxicity in patients with preeclampsia and eclampsia. If there is significant magnesium toxicity, stop the Magnesium Sulfate in 5% Dextrose Injection infusion and recheck serum magnesium concentration. Patients with renal impairment are at greater risk of magnesium toxicity because magnesium is excreted by the body solely by the kidneys [see Use in Specific Populations (8.6) ] . Urine output should be maintained at a level of 100 mL per 4 hours. Monitoring serum magnesium levels and the patient's clinical status is essential to avoid the consequences of overdosage in patients with preeclampsia. Discontinuation of the magnesium infusion is recommended when urine output is less than 100 mL every 4 hours to avoid magnesium toxicity, especially if serum creatinine is increasing progressively. 5.3 Risk of Elevated Blood Glucose Solutions containing dextrose should be used with caution in patients with known prediabetes or diabetes mellitus given the risk of elevated blood glucose. 5.4 Co-administration with Unapproved Tocolytics Do not use Magnesium Sulfate in 5% Dextrose Injection with unapproved tocolytics (e.g., beta adrenergic agents such as terbutaline, or with calcium channel blockers such as nifedipine). Serious adverse events including pulmonary edema and hypotension have occurred [see Drug Interactions (7) ] . 5.5 Aluminum Toxicity Magnesium Sulfate in 5% Dextrose Injection contains aluminum that may be toxic (Magnesium Sulfate in 5% Dextrose Injection contains less than 25 mcg/L of aluminum). Aluminum may reach toxic concentrations with prolonged parenteral administration in patients with renal impairment. Patients with renal impairment who receive parenteral concentrations of aluminum at greater than 4 to 5 mcg/kg/day, accumulate aluminum at concentrations associated with central nervous system and bone toxicity. Tissue loading may occur at even lower rates of administration. 5.6 Exacerbation of Myasthenia Gravis Magnesium Sulfate in 5% Dextrose Injection is contraindicated in patients with known myasthenia gravis. Use of magnesium sulfate in patients with underlying myasthenia gravis can precipitate a myasthenic crisis. Myasthenic crisis is a life-threatening condition characterized by neuromuscular respiratory failure. Symptoms of myasthenic crisis may include difficulty swallowing, ptosis, facial droop, weakness and/or difficulty breathing that may require intubation. If myasthenic crisis is suspected, discontinue use of Magnesium Sulfate in 5% Dextrose Injection immediately. Secure the patient's airway. Consider intensive care unit admission and elective intubation, if respiratory failure is anticipated. Once the airway is secure, confirm the diagnosis. Therapies include plasmapheresis and plasma exchange or intravenous immunoglobulin (IVIG) and immunomodulating therapy in addition to high-dose glucocorticoids.

CONTRAINDICATIONS Magnesium Sulfate in 5% Dextrose Injection is contraindicated in patients: • with heart block or myocardial damage • in diabetic coma • with myasthenia gravis [see Warnings and Precautions (5.6) ] • Heart block or myocardial damage ( 4 ) • Diabetic coma ( 4 ) • Myasthenia gravis ( 4 , 5.6 )

DRUG INTERACTIONS Table 1 presents the potential clinical impact of medications that may be commonly administered concomitantly with Magnesium Sulfate in 5% Dextrose Injection in the clinical setting. Table 1: Potential Clinically Significant Drug Interactions with Magnesium Sulfate in 5% Dextrose Injection For drug incompatibility information [see Dosage and Administration (2.4) ]. Neuromuscular Blocking Agents Clinical Impact: • Potentiation and prolongation of neuromuscular blockade is possible with the concomitant use of magnesium sulfate and neuromuscular blocking agents [see Clinical Pharmacology (12.2) ] . • The underlying mechanism of this interaction may involve suppression of peripheral neuromuscular function by decreasing acetylcholine release, reduction of endplate sensitivity, and decreased muscle fiber excitability with magnesium sulfate therapy. Intervention: • Monitor respiration and the depth of neuromuscular blockade frequently (e.g., train-of-four monitoring) when a neuromuscular blocking agent is used concomitantly with Magnesium Sulfate in 5% Dextrose Injection. • Adjust the dosage of the neuromuscular blocking agent accordingly to maintain the desired level of musculoskeletal activity. The amount of reversal agent(s) required to achieve adequate reversal of the neuromuscular blocking agent(s) may also be increased. Examples: • Depolarizing neuromuscular blockers: succinylcholine • Non-depolarizing neuromuscular blockers: atracurium, cisatracurium, pancuronium, rocuronium, vecuronium Narcotics and/or Propofol Clinical Impact: • Potentiation and prolongation of analgesia and CNS depression is possible with the concomitant use of Magnesium Sulfate in 5% Dextrose Injection with narcotics and/or propofol. The potential for magnesium sulfate to affect other CNS depressants is unknown [see Clinical Pharmacology (12.2) ] . • The underlying mechanism of this interaction may involve antagonism of N-methyl-D-aspartate (NMDA) by magnesium sulfate therapy. Intervention: • Monitor the depth of CNS depression frequently using a reliable instrument. • Adjust the narcotic and/or propofol dosage accordingly to maintain the desired level of analgesia and sedation. Examples: • Narcotics and propofol Dihydropyridine Calcium Channel Blockers Clinical Impact: • An exaggerated hypotensive response is possible with the concomitant use of Magnesium Sulfate in 5% Dextrose Injection with dihydropyridine calcium channel blockers. The potential for magnesium sulfate to affect other calcium channel blockers (e.g., diltiazem and verapamil) is unknown [see Clinical Pharmacology (12.2) ] . Intervention: • Monitor vital signs (heart rate, blood pressure, respiration) frequently. • Supportive care and/or discontinuation of the calcium channel blocker may be required. Examples: • Amlodipine, clevidipine, felodipine, isradipine, nicardipine, nifedipine, nimodipine, and nisoldipine Drugs that May Induce Magnesium Loss Clinical Impact: • Reduced magnesium concentrations may impact efficacy Intervention: • Monitor magnesium concentrations frequently and adjust the Magnesium Sulfate in 5% Dextrose Injection dosage to maintain concentrations in the target range [see Dosage and Administration (2) ] . Examples: • Alcohol, aminoglycosides, amphotericin B, cisplatin, cyclosporine, digitalis, loop diuretics, thiazide diuretics • Neuromuscular blocking agents : Potentiation and prolongation of neuromuscular blockade is possible with the concomitant use of Magnesium Sulfate in 5% Dextrose Injection ( 7 ) • Narcotics and/or propofol : Potentiation and prolongation of analgesia and CNS depression is possible with the concomitant use of Magnesium Sulfate in 5% Dextrose Injection ( 7 ) • Dihydropyridine calcium channel blockers : An exaggerated hypotensive response is possible with the concomitant use of Magnesium Sulfate in 5% Dextrose Injection ( 7 ) • Drugs that may induce magnesium loss with concomitant use of Magnesium Sulfate in 5% Dextrose Injection : Alcohol, aminoglycosides, amphotericin B, cisplatin, cyclosporine, digitalis, loop diuretics, and thiazide diuretics ( 7 )

ADVERSE REACTIONS The following adverse reactions have been identified in clinical studies or postmarketing reports. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Cardiovascular: hypotension, circulatory collapse, cardiac depression including bradycardia Central Nervous System: central nervous system depression leading to respiratory paralysis, visual disturbances, flushing, sweating, hypothermia Metabolic: hypocalcemia with signs of tetany, hypermagnesemia Neurologic: lethargy, sedation, somnolence, myasthenic crisis Neuromuscular: depressed deep tendon reflexes, flaccid paralysis Pulmonary: decreased respiratory rate, pulmonary edema The most common adverse reactions are flushing, sweating, hypotension, depressed reflexes, flaccid paralysis, hypothermia, circulatory collapse, cardiac and central nervous system (CNS) depression proceeding to respiratory paralysis and hypocalcemia. Bradycardia, pulmonary edema, decreased respiratory rate, lethargy, sedation, somnolence, visual disturbances, and hypermagnesemia are also reported ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact WG Critical Care, LLC at 1-866-562-4708 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

CLINICAL PHARMACOLOGY Magnesium (Mg++) is an important cofactor for enzymatic reactions and plays an important role in neurochemical transmission and muscular excitability. Magnesium prevents or controls convulsions by blocking neuromuscular transmission and decreasing the amount of acetylcholine liberated at the end plate by the motor nerve impulse. Magnesium is said to have a depressant effect on the central nervous system, but it does not adversely affect the mother, fetus or neonate when used as directed in eclampsia or pre-eclampsia. Normal serum magnesium levels range from 1.3 to 2.1 mEq/liter. As serum magnesium rises above 4 mEq/liter, the deep tendon reflexes are first decreased and then disappear as the serum level approaches 10 mEq/liter. At this level respiratory paralysis may occur. Heart block also may occur at this or lower serum levels of magnesium. Magnesium acts peripherally to produce vasodilation. With low doses only flushing and sweating occur, but larger doses cause lowering of blood pressure. The central and peripheral effects of magnesium poisoning are antagonized to some extent by intravenous administration of calcium. With intravenous administration the onset of anticonvulsant action is immediate and lasts about 30 minutes. Following intramuscular administration the onset of action occurs in about one hour and persists for three to four hours. Effective anticonvulsant serum levels range from 2.5 to 7.5 mEq/liter. Pharmacokinetics: Absorption: Intravenously administered magnesium is immediately absorbed. Distribution: Approximately 1-2% of total body magnesium is located in the extracellular fluid space. Magnesium is 30% bound to albumin. Metabolism: Magnesium is not metabolized. Excretion: Magnesium is excreted solely by the kidney at a rate proportional to the serum concentration and glomerular filtration. Special Populations: Renal Insufficiency: Magnesium is excreted solely by the kidney. In patients with severe renal insufficiency, the dose should be lower and frequent serum magnesium levels must be obtained (see DOSAGE & ADMINISTRATION ). Hepatic Insufficiency: Magnesium is excreted solely by the kidney. No dosing adjustments are necessary in hepatic insufficiency. Drug-Drug Interactions: Drug induced renal losses of magnesium occur with the following drugs or drug classes: Aminoglycosides Amphotericin B Cyclosporine Diuretics Digitalis Cisplatin Alcohol