The effect of pyridoxine administration on melatonin secretion in normal men.

OBJECTIVES To determine pineal response to pyridoxine in normal men. MATERIAL AND METHODS Twelve healthy men were given orally pyridoxine (100 mg) or placebo at 1700h. Serum melatonin levels were determined every 30 minutes with simultaneous measurement of core body temperature between 1700h to 0300h. Polysomnographic sleep recordings were performed between 1800h to 2000h. RESULTS Serum melatonin levels after both placebo and pyridoxine showed a nocturnal rise occurring at 22:10+/-1:22h and 22:24+/-1:09h, respectively. The melatonin onset, peak, mean and area under the curve (AUC) values after pyridoxine (3.2+/-1.6 pg/ml, 47.2+/-22.6 pg/ml, 31.5+/-11.0 pg/ml and 173.5+/-138.4 pg/ml x min, respectively) were similar to the values after placebo administration (4.7+/-1.6 pg/ml, 53.9+/-26.0 pg/ml, 37.2+/-2.8 pg/ml and 205.3+/-137.8 pg/ml x min, respectively). CBT revealed a significant nocturnal decline but without significant difference between pyridoxine and placebo. Sleep amount and architecture were similar after the two treatments. CONCLUSIONS In adult man, the oral administration of 100 mg-pyridoxine during the evening hours has no effect on melatonin secretion nor does it alter CBT or sleep quality.