Variability in absorption lag time of pyridoxal phosphate under fasting and pre- and post-meal conditions

Inter‐individual variations in the absorption lag time of pyridoxal phosphate were determined after administration of an enteric‐coated tablet (EC) or a plain capsule (PC) to 113 healthy volunteers under fasting, pre‐meal, and post‐meal conditions. The absorption lag time of pyridoxal phosphate was assessed from the urinary excretion of 4‐pyridoxic acid after administration of EC and PC. Significantly larger lag times after administration of both formulations were observed under post‐meal conditions than under pre‐meal conditions (0.477 ± 0.315 h versus 0.081 ± 0.086 h for PC and 1.995 ± 1.345 h versus 1.064 ± 1.327 h for EC), indicating that the mean gastric emptying rates of both a solution and a tablet were delayed after food intake. The lag time for PC showed little inter‐individual variation with (0–1.2 h) or without food (0–0. 25 h), whereas that for EC showed markedly large inter‐individual variation, from 0.25 to 2.63 h (median, 1.5 h) in the fasting condition, from 0.25 to > 5.5 h (median 0.25 h) under pre‐meal conditions, and from 0.25 to > 5.5 h (median 1.25 h) under post‐meal conditions. The effect of food on the gastric emptying rate of a solution appears to be almost uniform, whereas that for a tablet is so unpredictable that a reliable absorption rate for an enteric‐coated tablet cannot be expected, particularly under pre‐ and post‐meal conditions.