Response of protracted neonatal hypocalcaemia to 1alpha,25-dihydroxyvitamin D3.

Six infants with protracted hypocalcaemia (5 classed as tetany of the newborn) had a mean plasma-calcium of less than 6-4 mg/dl and raised plasma-inorganic-phosphate. Four had been hypocalcaemic for longer than 2 weeks despite treatment with low phosphate formulae and extra calcium. All the infants were treated with 1alpha,25-dihydroxyvitamin D3 (1alpha,25-(OH)2D3), usually in a dose of 0-05 mug/kg body-weight/day, administered intravenously for 5--12 days. The plasma-calcium levels began to rise within 24 h after starting 1alpha,25-(OH)2D3 treatment, increased above 7-5 mg/dl within 3 days, and reached the normal range within 8 days. Four of the infants remained normocalcaemic when 1alpha,25-(OH)2D3 was discontinued, but two infants became hypocalcaemic again and required long-term treatment. 1alpha,25-(OH)2D3 has been found safe and dependable as treatment for protracted neonatal hypocalcaemia.