Metabolic bone disease after chronic antacid administration in an infant.

OBJECTIVE: To describe a case of hypophosphatemia and metabolic bone disease (MBD) due to aluminum-containing antacids.

CASE SUMMARY: An 8-month-old white boy was brought to the emergency department due to irritability and pain with movement. Upon examination, the infant was irritable, unable to bear weight, had palpable clavicular bony lesions, point tenderness of the hips, and poor head control. The infant had lost several developmental milestones over the past 4 months (eg, ability to roll over) and had decreased appetite and minimal weight gain. Skeletal survey revealed multiple rib fractures, osteoporosis, and Ricketts. Hypophosphatemia (2.3 mg/dL; normal 3.2-6.3) and an elevated serum aluminum level (14 microg/L, normal 0-9) were noted. Past medical history was positive for gastroesophageal reflux. He had been started on ranitidine and aluminum hydroxide (1/2 teaspoonful per 6-ounce bottle) at 2 months of age. The infant's formula contained elevated aluminum levels. Further investigation showed that 1/2 tablespoonful instead of 1/2 teaspoonful of antacid had been added to each 6-ounce formula bottle for the prior 6 months; only 1 month of antacid therapy had been recommended. An objective causality assessment revealed a probable adverse drug event.

DISCUSSION: Phosphate-binding substances such as aluminum-containing antacids can bind large amounts of phosphorus, causing hypophosphatemia and MBD.

CONCLUSIONS: We report this case to increase awareness of the risk of hypophosphatemia and MBD (likely aluminum related) with use of over-the-counter aluminum-containing antacids in pediatrics, as well as the hazards of prescribing doses in "spoonful" units.