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Phillips' Cramp-free Side Effects

Generic name: magnesium oxide

Note: This document contains side effect information about magnesium oxide. Some dosage forms listed on this page may not apply to the brand name Phillips' Cramp-free.

Applies to magnesium oxide: oral capsule, oral tablet.


Follow all directions on the label and package. Use exactly as directed.

Get emergency medical help if you have signs of an allergic reaction: hives, difficult breathing, swelling of your face, lips, tongue, or throat.

Stop using magnesium oxide (the active ingredient contained in Phillips' Cramp-free) and call your doctor at once if you:

Common side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to magnesium oxide: compounding powder, oral capsule, oral tablet.


Frequency not reported: Hypermagnesemia, magnesium toxicity[Ref]

Magnesium toxicity symptoms may include: hypotension, nausea, vomiting, facial flushing, urine retention, ileus, depression, lethargy, muscle weakness, respiratory depression, arrhythmia, cardiac arrest, coma, and death.[Ref]


Frequency not reported: Diarrhea, nausea, abdominal cramping[Ref]


1. Guerrera MP, Volpe SL, Mao JJ (2009) "Therapeutic uses of magnesium." Am Fam Physician, 80, p. 157-62

2. National Institutes of Health (NIH) (2017) Magnesium: fact sheet for health professionals.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.