The most common adverse effects of oral supplements are diarrhea (18.6%) and gastric irritation (4.7%). Typically, doses above 350 mg/day (elemental) may be associated with adverse effects.
The interactions included in this section are relevant for oral supplementation and do not refer to other administration routes, although there may be an overlap.
AMINOGLYCOSIDES (E.G. GENTAMYCIN)
Drug may reduce absorption of Mg — monitor for signs and symptoms of Mg deficiency, as increased Mg intake may be required with long-term therapy.
Magnesium may enhance the hypotensive effect of calcium-channel blockers: monitor patients and their drug requirements — possible beneficial interaction.
Magnesium may decrease absorption of fluoroquinolone antibiotics — separate doses by at least 2 hours before or 4 hours after oral Mg.
LOOP DIURETICS AND THIAZIDE DIURETICS
Increased Mg intake may be required with long-term therapy because these drugs increase Mg loss — monitor Mg efficacy and status with long-term drug use.
Tetracyclines form insoluble complexes with Mg, thereby reducing absorption of both — separate doses by at least 2 hours.
Additive effect theoretically possible because high-dose oral Mg exerts antiarrhythmic activity according to one clinical study — observe patients taking this combination.
May increase the effects of supplemental Mg — observe patients taking this
Contraindications and Precautions
• Magnesium supplementation is contraindicated in renal failure and heart block (unless a pacemaker is present).
• Hypermagnesaemia can develop in patients with renal failure and receiving Mg-containing antacids or laxatives and with accidental Epsom salt ingestion.
• Overuse of magnesium hydroxide or magnesium sulfate may cause deficiencies of other minerals or lead to toxicity.
Pregnant women and nursing mothers are advised to consume sufficient Mg (see RDI in Dosage Range).