REDUCTION OF CIRCULATING 25-HYDROXYVITAMIN D BY ANTIPYRINE

1 Twenty‐four Asian vegetarians had significantly lower 25‐ hydroxyvitamin D (25‐OHD) levels and longer antipyrine half‐lives than twenty white non‐vegetarians (P less than 0.001). 2 Treatment with oral antipyrine over 4 or 5 weeks in seven vegetarian Asians and five racially different non‐vegetarians increased drug oxidation significantly in both groups as measured by a fall in antipyrine half‐ lives and a rise in serum gamma‐glutamyltranspeptidase levels and urinary 6 beta‐hydroxycortisol/17‐hydroxycorticosteroid ratios. 3 Antipyrine treatment produced a fall in circulating 25‐hydroxyvitamin D of around 60% in all subjects in whom pretreatment levels could be measured, independent of race and diet. 4. In the Caucasian non‐ vegetarian group 1,25 dihidroxyvitamin D levels, the most active metabolite of vitamin D, were also measured and remained unaltered despite a substantial fall in 25‐hydroxy substrate. 5 The acute fall in 25‐hydroxyvitamin D concentration with a maintained level of 1,25 dihidroxyvitamin D may represent the early changes of drug‐induced osteomalacia. 1979 The British Pharmacological Society