Etizolam: general

Etizolam is a thienodiazepine — a chemical cousin of classic benzodiazepines, with a thiophene ring standing in for one of the benzene rings [1]. It binds strongly at the benzodiazepine site on GABA-A receptors [1], and is reported to act there as an agonist with anxiolytic, sedative, hypnotic, amnesic, anticonvulsant, and muscle-relaxant effects [2][3].

In Japan, etizolam has been used since 1983 as a treatment for anxiety and sleep disorders, and it's marketed for anxiety treatment in some other countries too, sold as 0.25 mg, 0.5 mg, and 1.0 mg tablets [4][5]. It's also produced as an unapproved drug, in tablet and powder form [6], and it's commonly described as a New Psychoactive Substance or "designer" benzodiazepine [1]. This split matters: pharmaceutical etizolam, taken as prescribed, has few documented harms [7]. The harms that do show up are concentrated almost entirely in illicitly made pills, and almost always involve mixing with other drugs rather than etizolam alone [7].

Compared with diazepam, etizolam is more potent as an anxiolytic and less lethal on its own [7] — but "less lethal than diazepam" is not the same as safe, and it says nothing about what happens when it's combined with other depressants or with opioids, or when the actual dose in an illicit tablet is unknown. If you're using a product that didn't come from a pharmacy, treat the strength as a guess, not a known quantity.

References

1. Critical Review Report: Etizolam — World Health Organization / ECDD Repository
2. Etizolam: Uses, Interactions, Mechanism of Action — DrugBank Online
3. Substance Details: Etizolam — United Nations Office on Drugs and Crime (UNODC)
4. Etizolam (DEA Diversion Control Division) — U.S. Drug Enforcement Administration
5. Etizolam | C17H15ClN4S — PubChem (NCBI)
6. Etizolam - Expert Committee on Drug Dependence Information Repository — World Health Organization / ECDD
7. Etizolam: A rapid review on pharmacology, non-medical use and harms — PubMed / Drug and Alcohol Review