Which substance is not known to be a dissociative anesthetic?

The correct choice is determined by understanding the classifications of substances. Dissociative anesthetics are a category of drugs that cause a sense of detachment from the environment and self. They typically disrupt the normal functioning of the brain's neurotransmitters, particularly glutamate pathways.

Phencyclidine (PCP) is a well-known dissociative anesthetic that alters perceptions and can lead to behavioral changes. Ketamine is also classified as a dissociative anesthetic and is often used in medical settings for its anesthetic properties. DXM (dextromethorphan), while commonly used as a cough suppressant, can produce dissociative effects at higher doses and is occasionally classified alongside dissociatives in recreational contexts.

In contrast, methamphetamine is a powerful central nervous system stimulant that primarily increases dopamine levels in the brain, leading to effects of euphoria and heightened energy, rather than the dissociative effects associated with anesthetics. Therefore, it does not belong to the category of dissociative anesthetics, making it the correct answer to the question.