5-Hydroxytryptophan or 5-HTP is a naturally-occurring amino acid, a precursor to the neurotransmitter serotonin and an intermediate in tryptophan metabolism. It is marketed in the United States and other countries as a dietary supplement for use as an antidepressant, appetite suppressant, and sleep aid.
This reaction occurs both in nervous tissue and in the liver. 5-HTP crosses the blood-brain barrier, while 5-HT does not. Excess 5-HTP, especially when administered with Vitamin B6, is thought to be metabolized and excreted.
Research shows that co-administration with carbidopa greatly increases plasma 5-HTP levels. However, several studies have reported that 5-HTP is effective even without a peripheral decarboxylase inhibitor (e.g. carbidopa). Other studies have indicated the risk of a scleroderma-like condition resulting from the combination of 5-HTP and carbidopa.
A review article suggests that 5-HTP and other neurotrasmitter precursors might be effective for the treatment of depression.
Current research shows promise in using 5-HTP for treating children with night terrors. After six months of use 83.9% of the children treated with 5-HTP were free from their persistent sleep terrors.
Some persons with fibromyalgia find that 5-HTP improves their symptoms. Fibromyalgia sufferers report improvement in sleep, depression, pain and all major complaints related to fibromyalgia. Studies are continuing to refine dosage and continued use.
It is also used as a prophylactic against chronic daily headache. 5-HTP may also be useful in treatment for migraines, since studies have shown that migraines occur when serotonin levels are low.
Serotonin syndrome was not observed in several studies that augmented traditional antidepressant therapy with 5-HTP, even though the combination therapy was expected to increase the risk of serotonin syndrome above 5-HTP alone. Some users report high doses (300 mg and over) can produce nausea and vomiting.