5-HTP (pentahydroxytryptophan) for ADHD
5-HTP (pentahydroxytryptophan) is the precursor of serotonin. It can help to circumvent the limitation of serotonin synthesis from L-tryptophan.
Serotonin is in turn a precursor to melatonin.
Taking 5-HTP should always be supported by a doctor. An overdose can lead to serotonin syndrome, which can be very dangerous. Other simpler side effects such as diarrhea can occur, especially at the beginning of the intake, as most 5-HTP is converted to serotonin in the intestine, which can lead to increased intestinal activity. Only a small percentage crosses the blood-brain barrier.
As various amino acids compete for the transporters through the blood-brain barrier, an excess supply of one of these substances can impair the transport of other substances through the blood-brain barrier and
Individual case report:
A single person with ADHD reported that 5-HTP together with melatonin not only helped her to fall asleep, but also provided subjectively better sleep and better recovery, while melatonin alone made it easier to fall asleep, but she never felt particularly refreshed in the morning. Furthermore, 5-HTP also improved the existing irritable bowel syndrome and reduced the abdominal pain that occurred at night as a result.
Taking the recommended daily dose of 5-HTP further increased her ADHD symptoms, which could no longer be improved even by increasing the stimulant dose. Only a lower 5-HTP intake improved the overall condition.
This could result from the described competition of 5-HTP with other amino acids for the transporters through the blood-brain barrier, if in this case fewer precursors for dopamine synthesis reached the brain.
Serotonin synthesis also competes with dopamine synthesis for aromatic L-amino acid decarboxylase.
5-HTP should not be combined with L-dopa (for RLS), as the decarboxylase inhibitor contained in L-dopa medication also inhibits the conversion of 5-HTP into serotonin (same enzyme - same effect). As a result, too much 5-HTP enters the brain and can trigger serotonin syndrome.
Similarly, 5-HTP should not be combined with other medications that increase serotonin (e.g. antidepressants such as SSRIs, SNRIs, tricyclic antidepressants, St. John’s wort and others).