Many drugs/toxins cause nystagmus, particularly in overdose.  Vertical, horizontal, or rotary nystagmus may be noted.

The most common drug/toxin overdoses that cause nystagmus are the following:

• Anticonvulsants (phenytoin, carbamazepine, valproic acid, lamotrigine, topiramate)
• Ethanol
• Lithium
• Dextromethorphan
• Phencyclidine (PCP)
• Ketamine
• Lysergic acid diethylamide (LSD)