Demi Moore's friend called paramedics Monday night after the actress inhaled a dangerous amount of nitrous oxide ... TMZ has learned.
Sources tell TMZ ... one of Demi's friends who was at her home told emergency workers Demi was doing whip-its. A whip-it is a street name for a type of nitrous oxide inhalant.
The friend said she became upset when Demi had a reaction to a whip-it and lapsed into semi-consciousness.
It appears Demi had symptoms of a seizure -- after inhaling the nitrous.
A whip-it is not a common drug among people of Demi's age and social status. It's typically used by younger people who are looking for a cheap thrill.