Improvement in the radiographic lesions of rickets takes several weeks to become apparent. Patients with rachitic or osteomalacic bone changes may become hypercalcemic as the bones become remineralized and therefore take up less calcium from the blood. To decrease the risk of hypercalcemia, a downward adjustment of the calcitriol dose may be advisable once a reduction in serum alkaline phosphatase has been achieved. The single most important indicator of calcitriol overdose appears to be hypercalcemia as determined by accurate and frequent measurement of the serum calcium concentration. Signs of hypercalcemia such as polyuria, nocturia, polydipsia, nausea, vomiting, anorexia, weight loss, and constipation should be watched for but are less sensitive indicators of toxicity.
Most hypercalcemic patients are asymptomatic.
If hypercalcemia occurs, calcitriol is discontinued for 1 to 2 weeks or until hypercalcemia disappears. Hypercalcemia frequently resolves in 2 to 7 days. Kidney ultrasounds may be indicated yearly during calcitriol therapy. However, the clinical significance of the finding of nephrocalcinosis is not known. Calcitriol solution must be measured accurately and can be administered directly into the mouth of the infant.