Toxic or metabolic reasons could be the result of the following:
Alcohol intoxication
Amphetamines
Barbiturates
Benzodiazepines
Ketamine
Lithium
Lysergic acid diethylamide (LSD)
Methylenedioxymethamphetamine (MDMA)
Methylenedioxyamphetamine (MDA)
Other anticonvulsants or sedatives
Phencyclidine (PCP)
Phenytoin (Dilantin)
Salicylates
SSRIs
Thiamine deficiency
Wernicke's encephalopathy
Central nervous system (CNS) disorders, such as with a cerebellar problem, the nystagmus can be in any direction including horizontal. Purely vertical nystagmus is usually central in