Loss of consciousness

Loss of consciousness is a state in which a person cannot be roused and does not respond to voice, touch, or painful stimulation. It is distinct from ordinary sleep, which can be interrupted, and from heavy sedation, which still allows some response — the distinction matters because an unresponsive person cannot protect their own airway.

In the context of substance use, it occurs most commonly with CNS depressants: opioids, benzodiazepines, alcohol, and GHB/GBL each suppress the brain's arousal systems, and their combinations can do so synergistically. Dissociatives and general anesthetics produce loss of consciousness at higher doses through different pathways, typically by blunting sensory relay at the thalamus rather than suppressing arousal outright.

How it is done

Recognition follows a short sequence. The first step is verbal — speaking to the person and calling their name. If that produces no response, a firm physical stimulus is applied: a sternal rub or sustained pressure to the trapezius will rouse a heavily sedated person even when voice has failed. No reaction to either confirms unconsciousness.

The next check is the airway: visible chest rise, audible breath sounds, or felt airflow at the mouth and nose establishes whether breathing is adequate. If the person is breathing but cannot be roused, the recovery position — on one side with the head tilted to keep the airway open — is placed before anything else. It limits the risk of aspiration if vomiting occurs.

When it matters

Loss of consciousness during substance use is an emergency at the moment it is confirmed. Emergency services should be contacted immediately, alongside any other response — waiting to see whether the person recovers independently costs time that cannot be recovered if breathing stops.

Certain patterns heighten urgency: unresponsiveness following opioid use, where naloxone administration and emergency services go in parallel; any LOC involving GHB or GBL, where depth can be extreme and duration unpredictable; gurgling or snoring breath sounds, which indicate partial airway obstruction; and any situation where the substances involved are unknown.

A sitter being present changes the speed of response, not the threshold for calling emergency services.

What it cannot tell you

Confirming unresponsiveness establishes that a person cannot protect themselves. It does not identify the cause, indicate how long the state will last, or establish whether conditions are stable or worsening.

A person who appears stable — breathing regularly, normal color — can deteriorate without warning if a drug's peak effect is still building. Polysubstance combinations involving CNS depressants are particularly unpredictable: additive or synergistic respiratory suppression can deepen over time, after an initial reassuring assessment has already been made.

Loss of consciousness does not mean the peak has passed. Someone who goes unresponsive early in a substance's absorption window may face further suppression as more drug reaches systemic circulation. A stable appearance in the first minutes is not a reliable guide to the next hour.