From the FDA Drug Label
Diplopia and nystagmus have been noted following ketamine administration.
- Ketamine is the drug that causes nystagmus, but the type of nystagmus is not specified as lateral. The FDA drug label does not answer the question.
From the Research
Phencyclidine (PCP) is the drug of abuse that most commonly causes lateral nystagmus. This dissociative anesthetic produces horizontal, vertical, and rotatory nystagmus as a characteristic physical finding during intoxication. The lateral nystagmus occurs because PCP affects the vestibular system and cerebellar function by antagonizing NMDA receptors in the brain 1. Unlike alcohol, which typically causes horizontal gaze nystagmus at extremes of lateral gaze, PCP-induced nystagmus can be present even in the primary position of gaze. Other signs of PCP intoxication include hypertension, tachycardia, hyperthermia, agitation, and psychosis. While other substances like ketamine (another dissociative) can cause nystagmus, PCP is particularly known for this effect.
Some studies have reported on the effects of other substances, such as thiamine deficiency, which can cause nystagmus as part of Wernicke's encephalopathy 2, 3, 4. However, these cases are distinct from PCP-induced nystagmus and are typically associated with other symptoms such as confusion, ophthalmoplegia, and gait ataxia. Healthcare providers should be aware of this distinctive physical finding when evaluating patients with suspected drug intoxication, as it can help guide appropriate management and treatment decisions.
Key points to consider when evaluating a patient with suspected PCP intoxication include:
- Presence of lateral nystagmus, which can be horizontal, vertical, or rotatory
- Other signs of PCP intoxication, such as hypertension, tachycardia, hyperthermia, agitation, and psychosis
- Differentiation from other causes of nystagmus, such as thiamine deficiency or Wernicke's encephalopathy
- Importance of prompt recognition and treatment to prevent long-term neurological damage.