Severe selective magnesium malabsorption: tests of tolerance of oral magnesium supplements.

: Since his birth, we have been monitoring a 12-year-old boy suffering from selective severe magnesium malabsorption. Our essential problem is to prepare a form of galena with acceptable taste, tolerated by the digestive tract and well absorbed; also, the carrier compound must not cause short- or long-term side effects. An additional factor is the steadily increasing need for magnesium from 1 mmol/kg.d at 1 year to 14 mmol/kg.d at present age (345 mg/kg.d). The galena forms currently on sale were, with the exception of lactate and pyrollidone carboxylate, immediately rejected since they contain insufficient Mg2+. Following short trials resulting in diarrhoea, the other two preparations were also rejected. We then constituted - and also abandoned - our own galena compounds: aspartate (bitterness), aspartate + glycerophosphate (GLP) (bitterness), glutamate + GLP ('Chinese restaurant syndrome' and fear of the long term toxic effect of the glutamate), gluconate (excessive volume: 11/1 proportion with Mg2+). A recent test featuring GLP of Mg 40 g + cocoa butter 40 g + cocoa 10 g, brought about vomiting and diarrhoea, and was not adequately absorbed. The best tolerated formula is: Mg GLP 21.33 g; saccharose 6 g; aspartam 1 g; gelatin 0.5 g; citric acid, conserving agent, fruity aroma; water: qs 100 g. Such composition yields a caramel cream absorbed in five small portions, at a daily quantity of 375 g (80 g GLP Mg, 10 g Mg2+). Vitamin B6, which promotes intestinal absorption of magnesium, must be given separately in tablet form at a dose of 1 g/d, since it causes nausea if it is included in the Mg preparation.(ABSTRACT TRUNCATED AT 250 WORDS)