MAGNESIUM, MAGNESIUM SULFATE, PARENTERAL

For information on the use of oral magnesium hydroxide, refer to the monograph for Oral Antacidsin the GI section. Magnesium oxide and oral magnesium sulfate are also detailed in the monograph for Saline/Hyperosmotic laxatives in the GI section
Chemistry - Magnesium sulfate occurs as small, usually needle-like, colorless crystals with a cool, saline, bitter taste. It is freely soluble in water and sparingly soluble in alcohol. Magnesium sulfateinjection has a pH of 5.5-7. One gram of magnesium sulfate hexahydrate contains 8.1 mEq ofmagnesium. Magnesium sulfate is also known as Epsom salts.

Storage, Stability, Compatibility

Magnesium sulfate for injection should be stored at roomtemperature (15-30°C); avoid freezing. Refrigeration may result in precipitation or crystallization.
Magnesium sulfate is reportedly compatible with the following intravenous solutions and drugs:dextrose 5%, calcium gluconate, cephalothin sodium, chloramphenicol sodium succinate, cisplatin, hydrocortisone sodium succinate, isoproterenol HCl, methyldopate HCl, metoclopramide HCl (insyringes), norepinephrine bitartrate, penicillin G potassium, potassium phosphate, and verapamil
HCl. Additional y, at Y-sites: acyclovir sodium, amikacin sulfate, ampicillin sodium, carbenicillindisodium, cefamandole naftate, cefazolin sodium, cefoperazone sodium, ceforanide, cefotaximesodium, cefoxitin sodium, cephalothin sodium, cephapirin sodium, clindamycin phosphate, doxycycline phosphate, erythromycin lactobionate, esmolol HCl, gentamicin sulfate, heparinsodium, kanamycin sulfate, labetolol HCl, metronidazole (RTU), moxalactam disodium, nafcillinsodium, oxacillin sodium, piperacillin sodium, potassium chloride, tetracycline HCl, ticarcillindisodium, tobramycin sulfate, trimethoprim/sulfamethoxasole, vancomycin HCl, and vitamin B-complex with C.
Magnesium sulfate is reportedly incompatible with alkali hydroxides, alkali carbonates, salicylates and many metals, including the following solutions or drugs: fat emulsion 10 %, calciumgluceptate, dobutamine HCl, polymyxin B sulfate, procaine HCl, and sodium bicarbonate.
Compatibility is dependent upon factors such as pH, concentration, temperature and diluents used.
It is suggested to consult specialized references for more specific information (e.g., Handbook on
Injectable Drugs by Trissel; see bibliography).

Pharmacology - MAGNESIUM, MAGNESIUM SULFATE, PARENTERAL

Magnesium is used as a cofactor in a variety of enzyme systems and plays a rolein muscular excitement and neurochemical transmission.
Uses, Indications - Parenteral magnesium sulfate is used as a source of magnesium in magnesiumdeficient states (hypomagnesemia), for adjunctive therapy of malignant hyperthermia in swine, andalso as an anticonvulsant.

Pharmacokinetics - MAGNESIUM, MAGNESIUM SULFATE, PARENTERAL

IV magnesium results in immediate effects, IM administration may requireabout 1 hour for effect. Magnesium is about 30-35% bound to proteins and the remainder exists asfree ions. It is excreted by the kidneys at a rate proportional to the serum concentration andglomerular filtration.
Contraindications/Precautions - Parenteral magnesium is contraindicated in patients with myocardial damage or heart block. Magnesium should be given with caution to patients with impairedrenal function. Patients receiving parenteral magnesium should be observed and monitored carefullyto avoid hypermagnesemia.

Adverse Effects, Warnings

Magnesium sulfate (parenteral) adverse effects are generally theresult of magnesium overdosage and may include drowsiness or other CNS depressant effects, muscular weakness, bradycardia, hypotension, respiratory depression and increased Q-T intervalson ECG. Very high magnesium levels may cause neuromuscular blocking activity and eventuallycardiac arrest.

Overdosage, Acute Toxicity

See Adverse Effects above. Treatment of hypermagnesemia is dependent on the serum magnesium level and any associated clinical effects. Ventilatory support andadministration of intravenous calcium may be required for severe hypermagnesemia.

Drug Interactions

When parenteral magnesium sulfate is used with other CNS depressantagents (e.g., barbiturates, general anesthetics) additive CNS depression may occur.
Parenteral magnesium sulfate with nondepolarizing neuromuscular blocking agents hascaused excessive neuromuscular blockade.
Because serious conduction disturbances can occur, parenteral magnesium should be used withextreme caution with digitalis cardioglycosides.
Concurrent use of calcium salts may negate the effects of parenteral magnesium.