Supplies L-5-Hydroxy-Tryptophan (5-HTP), the precursor to serotonin, a key neurotransmitter. Caution: Very high doses of 5-HTP can be metabolized peripherally and can trigger excess serotonin formation. 5-HTP is not recommended for pregnant or lactating women and should be avoided by those with any form of cardiovascular disease. 5-HTP should not be used by those taking serotonin, 5-HTP, or receptor agonists (naratriptan, sumatriptan, zolmitriptan).