People take 5-HTP supplements mainly to increase the levels of serotonin in their brains (i.e. to help them sleep, the elevate the mood and other reasons) but I've heard some horror stories about people having heart attacks and other serious side effects from taking it. I think most of these side effects are caused by the peripheral nervous system. 5-HTP is decarboxylated to 5-HT (serotonin) by a non selective amino acid decarboxylase (which is also involved in the synthesis of catecholamines and histamine). This enzyme is present in the PNS, not just the CNS so a major problem with taking 5-HTP is that much of it will be metabolised in the PNS before it reaches the brain. Any ideas on how this can be avoided? One possible way would be to take a drug that inhibits the amino acid decarboxylase but cannot cross the blood brain barrier. This would be a viable solution if it were a selective enzyme that decarboxylates 5-HTP but in this case, the drug would interfere with the synthesis of dopamine (I've never heard of dopamine in the PNS, is it just a CNS neurotransmitter), norepinephrine, epinephrine and histamine which may produce various side effects. Any other ideas?