28 Long-term Administration of 5-Hydroxytryptophan in Down's Syndrome

Abstract

Patients with trisomy-21 Down's syndrome have been demonstrated to have a depression of whole blood 5-hydroxytryptamine (serotonin) (5HT). In older mongol children 5HT levels are usually around 50 % of normal while in the newborn a wide variation of levels from normal to as low as 10 % can be demonstrated. Fourteen hypotonic babies with trisomy-21 have been given 5-hydroxytryptophan (5HTP) in an attempt to raise the whole blood 5HT. Oral 5HTP was begun in early infancy and has been continued since then in each patient. The level of 5HT in whole blood and 5-hydroxyindoleacetic acid (5HIAA) in the urine was monitored. Serial neurological examinations were recorded by motion picture and on forms identical with those of the M.R.C. Psychiatric Genetic Unit's study of 73 trisomic mongols (all those ascertained within one geographical area in a year).In all patients, after an initial period of fluctuation, the level of whole blood 5HT was maintained at normal or near-normal values and 5HIAA in the urine rose to high- or above-normal values. Following an increase in whole blood 5HT levels, an improvement in muscular tone was noted, often within 24 hours (motion picture demonstration). This improvement was consistently demonstrated compared to the M.R.C. group. No child has remained severely hypotonic. The effects of overdosage are projectile vomiting, diarrhea, opisthotonos and rigidity, motor restlessness and hypertension. Turning over at an earlier age than normal appears to be due to a combination of rigidity and motor restlessness. It can be stopped by reducing the dose. The children in this series are too young for any statement to be made about developmental milestones. No implications as to intelligence are warranted. (APS)