Long-Term Bioavailability After a Single Oral or Intramuscular Administration of 600,000 IU of Ergocalciferol or Cholecalciferol: Implications for Treatment and Prophylaxis

Abstract

A po dose of 600,000 IU of D₂ or D₃ is initially more effective in increasing serum 25(OH)D than the equivalent im dose and is rapidly metabolized. Our RIA assay for 1,25(OH)₂D may not recognize 1,25(OH)₂D₂.