Magnesium Sulfate (Epsom Salts) for Dogs and Cats

Magnesium sulfate, also known as Epsom Salts, has many uses including laxative, electrolyte replacement, anticonvulsant and, in human – as well as dog and cat – medicine, bronchodilator in patients with poor response to beta agonists.

Magnesium is a cofactor in many enzymatic processes in the body and is involved in muscular excitement and neuromuscular transmission. Magnesium sulfate controls seizures by blocking neuromuscular transmission and decreasing the amount of acetylcholine released at the motor end plate.

Following intravenous administration, its anticonvulsant effect is virtually immediate and lasts about 30 minutes. Following intramuscular injection, the onset is slower (1 hour) and duration of action is longer (3 to 4 hours).

Magnesium sulfate is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian. This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.

Brand Names and Other Names for Magnesium Sulfate

This drug is registered for use in humans only.

• Human formulations: Magnesium sulfate (generic, various manufacturers).
• Veterinary formulations: None (pure)

Magnesium sulfate is available as an injectable form. Concentrations may include: include:

• 12.5 percent solution (1 mE/mL) in 8mL vials
• 50 percent solution (4 mE/mL) in 2 and 10mL amps, 10, 20, and 50 mL vials and 5 and 10 mL disposable syringes and 2 mL fill in 5 mL vials

Uses of Magnesium Sulfate for Dogs and Cats

The following are possible uses of magnesium sulfate:

• Anticonvulsant
• Electrolyte replacement in hypomagnesemia
• Laxative (oral treatment)
• Bronchodilator
• Treatment of life-threatening cardiac arrhythmias
• Treatment of malignant hypothermia (especially. in swine)

Epsom Salts for Pets: Precautions and Side Effects

Magnesium sulfate should be used with caution and at lower doses in patients with impaired renal function because it is cleared via the kidneys. It is contraindicated in patients with myocardial damage or heart block.

Side effects of magnesium sulfate are central nervous system depression, erythema, hypotension, circulatory collapse, and myocardial depression. Overdose can cause respiratory paralysis, asystole, and heart block.

Normal serum levels of magnesium are between 1.5 and 3 mEq/L. Serum levels in the range of 4 to 7 mEq/L are “therapeutic” when magnesium is being employed for treatment of convulsions. At levels of 7 to 10 mEq/L toxic signs appear, e.g. hypotension, loss of deep tendon reflexes, and narcosis.

Higher levels may result in respiratory paralysis, cardiac conduction defects, and ultimately cardiac arrest.

When magnesium sulfate is to be administered over an extended period of time monitoring of the serum concentration is indicated. Also, serum calcium should be monitored as this may drop. Urine output should be sustained during treatment by means of appropriate fluid replacement therapy.

Epsom Salt Drug Interactions

Magnesium sulfate may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with magnesium sulfate. Such interactions may include:

• When mixed with certain other injectable drugs, incompatibility may occur. These drugs include alkali hydroxides, alkali carbonates, salicylates, and many metals.
• Magnesium sulfate potentiates neuromuscular block caused by no-depolarizing neuromuscular blockers and succinylcholine and should be used with caution when muscle relaxants are being in effect.
• Magnesium sulfate should be used with extreme caution in patients treated with digoxin otherwise serious conduction disturbances may occur.
• Additive CNS depressant effects may occur if magnesium sulfate is used at the same time as general anesthetics.

Dosing Information of Magnesium Sulfate for Dogs and Cats

The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. The dosage prescribed may vary depending on the reason for prescribing. In dogs and cats, the usual dose for treatment of hypomagnesemia is 0.75 to 1.0 mEq/kg/day as a constant intravenous infusion. The dosage may be decreased after a couple days to about half the dose. It is often supplemented for several days. In dogs and cats, the usual dose for treatment of treatment of life-threatening ventricular arrhythmias, it is often given at 0.3 to 0.5 mE/kg over 5 to 15 minutes by injection.

Medication should never be administered without first consulting your veterinarian.