Why chronic microdosing might [be risky to the] heart
There have been several FDA-approved medications with 5HT2B receptor activation withdrawn from the US market due to the risk of VHD with heart valve thickening and murmurs: Fen-Phen (fenfluramine/phentermine) and Redux (dexfenfluramine) in 1997 and Permax (pergolide) in 2007.
Roughly 25% of patients taking these medications daily developed new onset VHD according to incidence statistics from the medical literature. This Ki value data showed that D-LSD and psilocin had an even stronger 5HT2B affinity than serotonin at the same receptor, which suggests that chronic LSD or psilocybin dosing may potentially have an even greater risk of VHD than norfenfluramine. This is a troubling statistic, since the psychedelics LSD and psilocin (psilocybin’s active metabolite) most frequently used for chronic microdosing also bind to the 5HT2B receptor, in addition to their better-known acute “psychedelic” 5HT2A receptor effects (PDSP certified data, n.d.; Knight et al., 2004).