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Magnesium sulphate

Last updated on 08/07/2021.

Overview   |   Dosage   |    Side Effects   |   Precautions  |   Tips  |   Where To Buy  

GENERIC NAME: Magnesium sulphate

ALTERNATIVE NAME: Magnesium sulfate



DRUG CLASS: Anticonvulsants

SUB CLASS: Electrolytes

USED FOR: Magnesium deficiency, Prevention and treatment of preeclampsia/eclampsia

AVAILABLE DOSAGE FORMS: 49.3% (injection)

What is Magnesium sulphate for?

Magnesium sulphate belongs to the class of medication called electrolytes. It is indicated for the treatment and prevention of hypomagnesemia, and severe preeclampsia or eclampsia, which are conditions of hypertension-induced seizures in pregnant women.

How to use it?

Magnesium sulphate can be injected intravenously or intramuscularly. Prior to injection, 49.3% solution should be diluted first by professionals. The total adult daily dose should not exceed 30-40 g of magnesium sulfate per day.

For mild hypomagnesemia:
Adults: 1 g (8mEq) magnesium sulfate intramuscularly every 6 hours for 4 doses

For severe hypomagnesaemia:
Adults: 5 g magnesium sulfate by slow intravenous infusion over 3 hours.

To prevent hypomagnesaemia when receiving total parenteral nutrition:
Adults: 0.5-3.0 g magnesium sulfate (4-24 mEq) daily
Infants: 0.25-1.25 g magnesium sulfate (2-10 mEq) daily

To prevent and treat preeclampsia or eclampsia in pregnant women:
Initiate intravenous dose of 4 g magnesium sulfate, followed by an intramuscular dose of 4-5 g (or infusion of 1-2 g/h) into each buttock. This may be followed by a dose of 4-5 g into alternate buttocks every four hours as needed.

What are the side effects of Magnesium sulphate?

Common side effects of magnesium sulphate include flushing, hypotension, and hypermagnesemia.

Who should not take Magnesium sulphate?

– People who are allergic to Magnesium sulphate or any component of the formulation
– Patients with heart block, myocardial damage, or renal failure
– Should not be administered to pregnant women in the two hours prior to delivery, unless it is the only therapy available to prevent eclamptic seizures

Pharmacist Tips:

– Talk to your doctor if you are breastfeeding.
– Hypermagnesemia may occur, especially in patients with renal failure. Report any signs of hypermagnesemia including muscle weakness, muscle paralysis, trouble breathing and abnormal vision.

Common dosing schedule:

Some common medications Magnesium sulphate may interact with:
– Bisphosphonates, e.g. Alendronate, Risedronate

Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.

Where to buy Magnesium sulphate in Hong Kong?

In Hong Kong, Magnesium sulphate is a prescription only medicine, and requires a prescription from a doctor to be purchased in a pharmacy. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.

For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at

Need more information?

For detailed information about the use of Magnesium sulphate in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.