title: The influence of phenobarbital on biotransformation of 25-hydroxycholecalciferol.
abstract: Altered vitamin D metabolism has been implicated as a cause of anticonvulsant-induced osteomalacia. Previous studies have demonstrated accelerated biotransformation of vitamin D3 to 25-hydroxycholecalciferol (25-OHD3). However, it is not known whether the 25-OHD3 is metabolized to 1,25-dihydroxycholecalciferol (1,25-(OH)2D3), the tissue-active metabolite of vitamin D3. This study using rats was undertaken to study the influence of phenobarbital on the biotransformation of 25-OHD3 to 1,25-(OH)2D3. The disappearance rate of 25-OHD3 was virtually the same in the pheno-barbital-treated group (re = 0.0615 pmole/min) and the control group (re - 0.0549 pmole/min). Similarly, the appearance rate of 1,25-(OH)2D3 was virtually the same in the treated group (ra = 0.0133 pmole/min) and the control group (ra = 0.0134 pmole/min). These data suggest that phenobarbital does not affect the biotransformation of 25-OHD3 to 1,25-(OH)2D3. The implication of this observation is that altered vitamin D metabolism does not account for phenobarbital-induced osteomalacia.
mesh_terms: D000818:Animals; D001711:Biotransformation / Q000187:drug effects; D006887:Hydroxycholecalciferols / Q000032:analysis / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D010018:Osteomalacia / Q000139:chemically induced; D010634:Phenobarbital / Q000009:adverse effects / Q000494:pharmacology*; D051381:Rats; D013997:Time Factors
chemical_list: D006887:Hydroxycholecalciferols; D010634:Phenobarbital