chloral hydrate is a sedative hypnotic agent which acts via GABA receptors and is metabolised by RBC's to trichloroethanol within ~4 minutes, and then hours later is metabolised further to trichloroacetic acid.
overdoses > 3-10g in an adult can be fatal via a variety of mechanisms including:
cardiotoxicity - VT/VF (avoid use of sympathomimetics to maintain BP)
hypotension
GIT erosive effects
hepatotoxicity
nephrotoxicity
CNS depression, especially when combined with other CNS depressants such as alcohol, barbiturates
long-term use of chloral hydrate is associated with a rapid development of tolerance to its effects and possible addiction as well as adverse effects including rashes, gastric discomfort and severe renal, cardiac and hepatic failure.