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.
Rumer was visibly distraught and concerned Tuesday afternoon ... as she spoke on the phone. Rumer and a nearby friend had hospital visitor's passes on their jackets.
TMZ broke the story ... Demi was rushed to the LA area hospital on Monday night. Demi's people say she is staying at the hospital to seek "further professional assistance" to treat exhaustion and deal with substance abuse issues.
Demi Moore was rushed to the hospital Monday night ... and we're told the issue is substance abuse.
Law enforcement tells us a 911 call was placed at 10:45 PM Monday night. Paramedics responded to Demi's L.A. home and after assessing her for a half hour, she was transported to a local hospital.
Sources tell us she is being placed in a facility to "seek further professional assistance." Our sources say the treatment is for substance abuse.
Demi's rep tells TMZ, "Because of the stresses in her life right now, Demi has chosen to seek professional assistance to treat her exhaustion and improve her overall health. She looks forward to getting well and is grateful for the support of her family and friends."
Ashton Kutcher's style wasn't cramped at all in the wake of Demi Moore's health crisis -- he was partying Tuesday in Sao Paulo, Brazil at a Bruno Mars concert and a nightclub.
We put a call in yesterday to Ashton's rep for comment on Demi's situation, but so far ... radio silence.
Demi Moore has dropped out of her upcoming movie, "Lovelace," TMZ has learned.
Demi's reps tell us ... they just got word she will no longer do a cameo for the flick.
TMZ broke the story ... Demi was rushed to the hospital Monday night for a substance abuse problem. She is currently receiving professional help at a treatment facility.