In addition, in the Phase 1 clinical trial in healthy volunteers using a randomised, double-blind, placebo-controlled single- and multiple-dose Phase 1 clinical trial, the safety and pharmacokinetics of the intravenous administration of TB-4 was evaluated. From this, intravenous administration of TB-4 appears to be safe and well-tolerated by all subjects with no dose limiting toxicity or serious adverse events reported.
A 2002 review concluded that although the data evaluated suggests that 5-HTP is more effective than placebo in the treatment of depression, the evidence was insufficient to be conclusive due to a lack of clinical data meeting the rigorous standards of today. More and larger studies using current methodologies are needed to determine if 5-HTP is truly effective in treating depression. In small controlled trials 5-HTP has also been reported to augment the antidepressant efficacy of the antidepressant clomipramine.