tree frog said:

There are risks of cardiac fibrosis and valvulopathy associated with microdosing daily.  Four on and three off is likely safer.  But if you're taking another medication that targets this receptor, or have a heart condition already, the risks would be higher.

And LSD, with its longer half-life and greater binding efficacy, would pose an even larger risk than psilocybin/psilocin.

Quote:

Sustained overstimulation of 5-HT2BR can cause cardiac fibroblasts to proliferate and become deposited in abnormal quantities, causing cardiac valves to thicken and function abnormally, which can ultimately manifest as valve fibrosis and VHD...

...  Thus, it appears that a microdose of LSD may indeed be large enough to raise the risk of VHD. Similarly, a small dose of 3 mg psilocybin raises plasma concentrations of psilocin to 2.3 ng/mL, comparable to the levels seen after the pro-fibrotic drug pergolide, which has a somewhat weaker affinity (Table 1). This suggests that the typical doses used in microdosing could potentially be enough to trigger fibrosis or VHD in a similar manner to other drugs.

---

https://journals.sagepub.com/doi/full/10.1177/02698811231225609

---

tree frog said:

...
But the first I heard about it was in a video someone, maybe Rev in fact, posted about risk factors for psychedelics.  It was a researcher who stated that microdosing should have breaks.  As chronic stimulation of a receptor in the heart that psychedelics bind to is associated with vascular heart disease.
...

---