GHB/GBL has a half-life of about 30 minutes. If breathing stays stable and no polydrug components are added, the person typically sleeps it off.
But: this is not an assessment that laypeople should make at home. Respiratory arrest with GHB/GBL happens suddenly, without warning. Polydrug use with alcohol, benzodiazepines, or opioids increases the risk massively.
There is no antidote for GHB. The only emergency treatment is securing the airway and monitoring breathing. Naloxone does not help.
Aspiration pneumonia after vomiting is a common secondary complication — so keep them in the recovery position consistently.