What is the exception that causes CNS depressants to potentially dilate pupils?

Methaqualone, often known by the brand name Quaalude, is a central nervous system depressant that, unlike many other members of its class, can occasionally cause pupil dilation as an atypical effect. Although CNS depressants generally lead to miosis, or constricted pupils, methaqualone can lead to mydriasis, or dilated pupils, particularly in higher doses or when combined with other substances.

This distinction makes methaqualone a unique case among CNS depressants, showcasing that the effects of substances can vary widely depending on their chemical nature, dosage, and the context in which they are consumed. Understanding this helps drug recognition experts be alert to the potential for atypical reactions, which can be critical during assessments or investigations of suspected substance use.