Possible Interaction: Phenobarbital and Vitamin D

“However, both in the phenobarbital and the placebo groups, vitamin D supplementation raised the circulating 25-OHD concentration (p less than 0.05).”

“Treatment with dexamethasone, phenobarbital , rifampicin, or 1α,25-dihydroxyvitamin D3 resulted in 5.8-fold, 13.4-fold, 9.8-fold, or 95.0-fold induction of CYP3A4 expression relative to that in the untreated controls, respectively.”

“Conclusion: This case report highlights the importance that clinicians caring for children on vitamin D and its analogues are aware of the interaction with phenobarbitone , which can result in symptomatic hypocalcaemia.”

“Since medication with phenytoin/phenobarbitone reduces vitamin D levels in serum and intake of this vitamin is positively correlated to myocardial infarction, we suggest that vitamin D might be a factor to be considered.”

“The [3H]25(OH)D3 production was increased during PB administration by a factor of 3-5 times over the pre- or post-PB period.”

“ Phenobarbital has been postulated to impair hepatic conversion of vitamin D to 25-hydroxyvitamin D [25(OH)D] either by accelerating the conversion of vitamin D to biologically inactive products or by directly inhibiting 25(OH)D production.”

“The effect of a dose of phenobarbital documented to decrease circulating 25(OH)D levels on hepatic vitamin D metabolism has been investigated in rachitic rats with a recycling in vitro hepatic perfusion system.”

“Abstract Diphenylhydantoin or phenobarbital adminstered for 25 days to Vitamin D-deficient rats inhibited liver calciferol 25-hydroxylase activity.”

“Prolonged treatment with phenobarbitone depleted the tissue radioactivity of rats given radioactive vitamin D 3 .”

“In vitamin D‐deficient growing rats, diphenylhydantoin and pheno‐barbital significantly retarded the rate of growth: at 14 days the mean gain in weight in percent was lower in treated animals than in controls, the three groups receiving vitamin D supplements 0.25 IU/day.”