Central nervous system
Common
drowsiness
mental confusion
insomnia
headache
ataxia

Rare
paranoid psychosis
increased libido
exacerbation of depression

Gastrointestinal
dyspepsia
vomiting
nausea
cramps
constipation
diarrhea
stomach pain
loss of appetite
weight loss
gum enlargement
swelling of tongue
abnormal liver function

Genitourinary
microscopic hematuria
vaginal bleeding

Blood
The following can occur with or without bone marrow loss:

pancytopenia
agranulocytosis
leukopenia
eosinophilia

Skin
urticaria
systemic lupus erythematosus
Stevens–Johnson syndrome
hirsutism
pruritic erythematous rashes

Eyes
myopia

Drug interactions
Valproates can either decrease or increase the levels of ethosuximide; however, combinations of valproates and ethosuximide had a greater protective index than either drug alone.It may elevate serum phenytoin levels. Mechanism of action
The mechanism by which ethosuximide affects neuronal excitability includes block of T-type calcium channels, and may include effects of the drug on other classes of ion channel. The primary finding that ethosuximide is a T-type calcium channel blocker gained widespread support, but initial attempts to replicate the finding were inconsistent. Subsequent experiments on recombinant T-type channels in cell lines demonstrated conclusively that ethosuximide blocks all T-type calcium channel isoforms. Significant T-type calcium channel density occurs in dendrites of neurons, and recordings from reduced preparations that strip away this dendritic source of T-type calcium channels may have contributed to reports of ethosuximide ineffectiveness. In March 1989, Coulter, Huguenard and Prince showed that ethosuximide and dimethadione, both effective anti-absence agents, reduced low-threshold Ca2+ currents in T-type calcium channels in freshly removed thalamic neurons. In June of that same year, they also found the mechanism of this reduction to be voltage-dependent, using acutely dissociated neurons of rats and guinea pigs; it was also noted that valproic acid, which is also used in absence seizures, did not do that.
For example, the Giant Mine in Canada processed substantial amounts of arsenopyrite-contaminated gold ores. References
External links
"Arsenic trioxide". Drug Information Portal. U.S. National Library of Medicine. Case Studies in Environmental Medicine: Arsenic Toxicity
"Arsenic and Arsenic Compounds". Summaries & Evaluations. International Agency for Research on Cancer (IARC). February 1998.
International Chemical Safety Card 0378
Safety Data Sheet from American Elements
NIOSH Pocket Guide to Chemical Hazards
NTP Report on Carcinogens – Inorganic Arsenic Compounds
Institut national de recherche et de sécurité (1989). "Trioxyde darsenic." Fiche toxicologique n° 89. Paris:INRS. (in French)