Which three drug categories commonly cause Horizontal Gaze Nystagmus (HGN)?

Horizontal Gaze Nystagmus (HGN) is an important indicator in the field of drug recognition that is commonly associated with several drug categories. HGN occurs when there is a dysfunction in the vestibular system or the areas of the brain responsible for controlling eye movements, leading to an involuntary jerking of the eyes. The correct answer highlights three drug categories known to significantly affect the central nervous system and contribute to HGN.

CNS depressants, which include substances such as alcohol and sedative medications, are well-documented to impair coordination and motor function, leading to observable symptoms like HGN. Dissociative anesthetics such as PCP or ketamine can also produce effects that may cause nystagmus, affecting a person's gaze control. Inhalants, which alter brain chemistry quickly and can create significant nervous system impairment, are similarly linked to this eye movement phenomenon.

Together, these categories represent drugs that are known to cause pronounced impairment in cardiovascular and neurological functions, making them associated with the presence of HGN when assessing individuals suspected of drug influence. The combination of these three categories as causes of HGN offers a comprehensive view of how different substances impact motor functions and eye movement control.