2C-B: general

2C-B is a synthetic phenethylamine and schedule I substance in the United States [1]. It was synthesised by Alexander Shulgin in 1974 [2]. Its effects are dose-dependent [1].

Effects typically last four to eight hours [3]. Plan the rest of your day, and who's around you, on that window.

A recent observational study found increased heart rate and blood pressure after 2C-B use [2]. 2C-B may be dangerous for those with heart conditions [2] — if that's you, the risk calculus here is different and worse. If you don't know your cardiovascular status, that's worth finding out before, not after.

Nothing here tells you a safe dose, and nothing here tells you 2C-B is broadly dangerous at typical doses either — only that dose changes effect, that effects run several hours, and that one study found increased heart rate and blood pressure afterward. Treat those as the three facts to plan around: go in knowing how much you're taking, expect to be affected for most of an evening, and don't treat cardiovascular risk as someone else's problem.

References

1. 4-Bromo-2,5-Dimethoxyphenethylamine (Street Names: 2C-B, Nexus, 2’s, Toonies, Bromo, Spectrum, Venus) — U.S. Drug Enforcement Administration
2. 2C-B | Drug Science — Drug Science
3. 2C-B - Alcohol and Drug Foundation — Alcohol and Drug Foundation