It is really difficult with the purging and super scary. Our d. was diagnosed with restrictive AN with purging and honestly what helped in her case was having the behavior interrupted by a 3 month stay in a pretty serious program where she was simply not allowed to go to the bathroom after eating. After that she was put on Fluoxetine. When she came home I checked the bathroom after she would go in. For a long time. Also when she came home I would also try to sit with her after eating and either talk or watch TV together to distract her from anything she might be thinking after eating a meal. You could try asking your d. to use the bathroom before meals and then sit with her afterwards and distract with tv or banagrams or scrabble or netflix or making crafts or knitting or whatever you can come up with that she likes, and let her know the bathroom is off limits and see if that helps.
We also kept talking to her about the physical damage it could do to her body.
There have been some studies with patients who purged using fluoxetine HCL vs. a placebo and they showed that there was some symptom reduction in the group who was administered the Fluoxetine. It is the only medication approved by the FDA to treat purging. There is also some clinical evidence backed up by studies that in a weight restored patient with Anorexia taking the prozac can help to avoid relapse. I don't think that there is any conclusive medical evidence, however, that prozac can help with weight restoration.
Here is a link which has some info and I wrote what seem to be the relevant parts below:
Fluoxetine. The evidence for the use of fluoxetine (Prozac®, Eli Lilly) in the treatment of bulimia nervosa comes in the form of various case reports, systematic studies, and double-blind, randomized placebo controlled trials. In a double-blind, placebo-controlled study by Halmi, et al., 382 patients were randomly assigned to receive fluoxetine or placebo at a dose of 20mg or 60mg daily for eight weeks.9,10 Treatment with the lower dose of fluoxetine resulted in reductions in binge eating and vomiting compared with placebo (45 vs. 33% and 29 vs. 5%, respectively). Those receiving 60mg of fluoxetine had even greater improvement with a 67-percent reduction in binge eating and a 56-percent reduction in vomiting.
Anorexia nervosa. Despite initial promise, none of the medicines available have been shown to be very effective on their own in the treatment of anorexia nervosa. The APA guidelines state that psychotropic medications should not be used as the sole or primary treatment for anorexia nervosa, but they can be considered for the prevention of relapse in weight restored patients or to treat depression or obsessive compulsive disorder.5
Is her md doing bloodwork and checking her potassium levels? Low potassium levels can be indicitive of purging and can have health risks.
Wishing for all the best for your daughter,