Advice

Overview for healthcare professionals

Overview for healthcare professionals

Oral magnesium glycerophosphate is used to prevent recurrence of symptomatic hypomagnesaemia in people who have already been treated for this condition, generally by intravenous infusion, which is the indication being assessed in this evidence summary.

Regulatory status of oral magnesium glycerophosphate

Oral magnesium glycerophosphate does not have marketing authorisation in the UK for preventing recurrent hypomagnesaemia, or for any other indications. Therefore it is an unlicensed medicine in the UK.

In line with the guidance from the General Medical Council (GMC), it is the responsibility of the prescriber to determine the clinical need of the patient and the suitability of using oral magnesium glycerophosphate.

No other oral magnesium supplements have marketing authorisation in the UK for preventing recurrent hypomagnesaemia.

Evidence statements

  • Oral magnesium glycerophosphate is an option described in the British national formulary (BNF) and BNF for children for preventing recurrent hypomagnesaemia.

  • No clinical trials were found. Only 3 individual case reports on oral magnesium glycerophosphate for preventing recurrent hypomagnesaemia after treatment with an intravenous infusion in adults were identified.

  • Two reports described patients with short bowel syndrome[1],[2] and the third was in a patient taking a proton pump inhibitor[3]. In these 3 patients, oral magnesium glycerophosphate was not sufficient to maintain normal serum magnesium levels.

  • No evidence to support the use of oral magnesium glycerophosphate for preventing recurrent hypomagnesaemia in children after intravenous treatment was identified.

Summary of the evidence

This section gives a brief summary of the main evidence. A more thorough analysis is given in the Evidence review section.

Efficacy

No published clinical trials comparing the efficacy of oral magnesium glycerophosphate with any active comparator or placebo for preventing recurrent hypomagnesaemia after treatment with intravenous magnesium were identified.

Three case reports described the use of oral magnesium glycerophosphate for preventing recurrent hypomagnesaemia in adults after intravenous treatment. Two of the reports were in patients with short bowels due to surgical resection[1],[2]. In both patients, oral magnesium glycerophosphate was not sufficient to maintain serum magnesium levels. In 1 patient, switching to oral magnesium oxide resulted in maintenance of serum magnesium levels, but in the other patient this was still not sufficient and intravenous magnesium top ups were needed every 3–6 months. In the third report, hypomagnesaemia was associated with proton pump inhibitor use[3]. In this patient, magnesium levels remained low after oral magnesium glycerophosphate supplementation, but reverted to normal after the proton pump inhibitor was stopped.

No studies in children were identified.

Safety

Oral magnesium salts may cause diarrhoea[4],[5]. In patients with renal impairment, magnesium should be avoided or the dose reduced because there is an increased risk of toxicity[4],[6].

Cost effectiveness and cost

No studies on the cost effectiveness of oral magnesium glycerophosphate for preventing recurrent hypomagnesaemia after intravenous treatment were identified.

The BNF states that 24 mmol Mg2+ daily may be given to prevent recurrence of magnesium deficit in adults. Estimated costs for this daily dose are £21.18 for the oral solution, £23.62 for the oral suspension (Drug Tariff, December 2012), between £2.52 and £8.28 per day for tablets, and between £12.24 and £32.40 for capsules (Prescription Cost Analysis, England 2011).

In England in 2011, 25,900 prescriptions for oral magnesium glycerophosphate were dispensed in the community by the NHS, costing around £3.8 million (Prescription Cost Analysis, England 2011).


[1] Ross JR, Dargan PI, Jones AL (2001) A case of hypomagnesaemia due to malabsorption, unresponsive to oral administration of magnesium glycerophosphate, but responsive to oral magnesium oxide supplementation. Gut 48: 857–8

[2] Arasaradnam RP, Bolton RP (2002) Hypomagnesaemia due to malabsorption is not always responsive to oral magnesium oxide supplementation alone. Gut 50: 897

[3] Shabajee N, Lamb EJ, Sturgess I et al. (2008) Lesson of the week: omeprazole and refractory hypomagnesaemia. BMJ 337: 173–5

[4] British national formulary for children (2012)

[5] Merck Manual (2009) Disorders of magnesium concentration

[6] British national formulary (2012)