Hypomagnesaemia in children with cystic fibrosis (CF) is under-recognized.
We report a child with CF who developed significant hypomagnesaemia followi
ng intravenous (i.v.) treatment with aminoglycosides for exacerbations of P
seudomonas aeruginosa infection. Three additional cases have also been obse
rved. Investigations in two patients have revealed excessive renal loss of
magnesium. It is postulated that renal tubular damage secondary to the cumu
lative effects of repeated courses of aminoglycosides resulted in hypomagne
saemia, and we suggest screening for this problem by monitoring serum magne
sium regularly in all patients with CF receiving multiple courses of aminog
lycosides.