The content of this evidence summary was up-to-date in January 2013. See summaries of product characteristics (SPCs), British national formulary (BNF) or the MHRA or NICE websites for up-to-date information.
Magnesium glycerophosphate is a magnesium salt that is available as a tablet, capsule, liquid solution or liquid suspension for oral use.
The British national formulary (BNF) states that oral magnesium glycerophosphate is a suitable preparation to prevent recurrence of symptomatic hypomagnesaemia in people who have already been treated for this condition. This evidence summary looks at the use of oral magnesium glycerophosphate in patients who have previously been treated with an intravenous infusion of magnesium. Oral magnesium glycerophosphate does not have UK marketing authorisation for this or any other indication, and therefore it is an unlicensed medicine in the UK.
No published clinical trials comparing the efficacy of oral magnesium glycerophosphate with placebo or any form of active treatment for preventing recurrent hypomagnesaemia after treatment with intravenous magnesium were identified. The only evidence found was from 3 case reports describing the use of oral magnesium glycerophosphate for preventing recurrent hypomagnesaemia in adults after intravenous treatment.
Two of the 3 case reports concerned patients who had short bowel syndrome due to surgical resection. In both these patients, oral magnesium glycerophosphate was not sufficient to maintain serum magnesium levels after initial intravenous treatment. In 1 patient, switching from oral magnesium glycerophosphate 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. The third case report was of a patient with hypomagnesaemia associated with proton pump inhibitor use. In this patient, magnesium levels remained low after oral supplementation with magnesium glycerophosphate but reverted to normal after the proton pump inhibitor was discontinued, even after the magnesium supplement was stopped.
No studies of oral magnesium glycerophosphate for preventing recurrent hypomagnesaemia in children after intravenous treatment were identified.
The most frequently cited side effect of magnesium salts is diarrhoea.
'Evidence summaries: unlicensed or off-label medicines' summarise the published evidence for selected unlicensed or off-label medicines that are considered to be of significance to the NHS, where there are no clinically appropriate licensed alternatives. The summaries provide information for clinicians and patients to inform their decision-making and support the construction and updating of local formularies.
The summaries support decision-making on the use of an unlicensed or off-label medicine for an individual patient, where there are good clinical reasons for its use, usually when there is no licensed medicine for the condition requiring treatment, or the licensed medicine is not appropriate for that individual.
The strengths and weaknesses of the relevant evidence are critically reviewed within this summary, but this summary is not NICE guidance.
The following information has become available since this ESUOM was produced.
July 2015: Availability of a licensed magnesium salt
A licensed magnesium product has now been launched in the UK. Magnaspartate is indicated for treating and preventing magnesium deficiency. The cost of Magnaspartate (excluding VAT) is £8.95 for 10 sachets. Cost taken from MIMS, July 2015.
In line with the guidance from the General Medical Council (GMC), unlicensed or off-label medicines should be used only where there is no suitably licensed medicine that will meet the patient's need.