I have run several rounds of the Semax versions and Adamax and began P21 about a week ago. Begin with the basic Semax as others suggested to gauge your response. The first three are all Semax related while P21 works differently. It comes from a subset of Cerebrolysin and is meant to rebuild brain pathways through neurogenesis and better cognition. Real Adamax and P21 both carry an adamantane group that is required for better absorption and longer action. Without that group P21 is ineffective even when used intranasally.
These three stand out as the main options. Has anyone actually used all of them and can compare the effects? Semax has Russian research behind it and a track record of use with what looks like a reasonable safety record. Adamax has no studies I could locate, so everything about it stays theoretical with claims of greater strength, better absorption and improved brain penetration that have not been shown in people or animals. P021 has one mouse study showing higher BDNF and lower Alzheimer markers, but again nothing in humans. I want personal accounts because the cost gap between them is large.