• In a double-blind study, 89 children with Down's syndrome were given 5-hydroxytryptophan or pyridoxine hydrochloride in the first three years of life. The analysis of 5-hydroxyindole blood levels revealed that 5-hydroxytryptophan, pyridoxine, and the combination of 5-hydroxytryptophan and pyridoxine raised blood levels of 5-hydroxyindole equally well in 40% of the children. The assessment of muscle-tone ratings showed no significant difference among the study groups once children with moderate and severe congenital heart disease were excluded. Detailed studies of cognitive-adaptive function of children in the various groups found a significant difference on the Vineland Social Maturity Scale at ages 6, 12, 18, and 36 months; yet the source of significance was a negative interaction affecting children whose parents were able to comply with furnished guidance; these children showed consistently higher levels of accomplishment.
(Am J Dis Child 134:838-844, 1980)