Many Psychiatrists and mental health professionals have never really had to deal with anyone suffering from HPPD.  I would strongly discourage going to a drug treatment center because this disorder really has nothing to do with dependency.  

Find a psychiatrist that has experience with this disorder, preferably one that is a member of the APA (American Psychiatric Assoc.)

To be honest, one of the few specialists in this field is Dr. Henry Abraham.  He has written many papers on the subject and has been on the forefront of research for years.  His contact information can be obtained via e-mail request.

Anyone with additional contacts can also e-mail me, and I will make this information available via the web site.

Possible Treatment Medications

While these medications may have been shown to improve cases of HPPD in certain journal articles, much of the evidence is anecdotal at best.  Hallucinogens are believed to act as serotonin2 partial agonists in the human brain, but the reasons some of these medications help the symptoms are unknown.

Medications that originally were believed to improve symptoms of HPPD theoretically, tended to do just the opposite.  These meds are catagorized as atypical antipsychotics, and include Risperidone, Clozapine*, Zyprexa, and Sertindole.  These meds are potent serotonin2a(5HT2A) antagonists, and in a study have actually shown to exacerbate HPPD panic/anxiety symptoms(well Risperidone, though all these meds work around the same general mechanism = 5HT2A antagonism + Dopamine2 antagonism).  On the other hand, atypical antipsychotic medications have been casually related to the improvement of depersonalization/derealization symptoms for some. Anecdotal reports from some sufferers have suggested that Zyprexa and newer antipsychotics have improved symptoms considerably.  These newer antipsychotics are not generally linked to the long-term effects of older meds.*  They are usually considered safe, especially in short-term, quantative runs....

Research

This leads us to research.  What has been done to find a "magic bullet" for treating HPPD.

--It is now thought that HPPD is possibly a genetic disorder where LSD and other hallucinogens may alter inhibitory neurons in the perceptual pathways of the brain(in susceptible individuals).  These are the systems that filter the senses (well, mainly sight, possibly sound) into a full understandable picture.

--Research has recently been done where people were given an intermuscular dose of an unamed, potent Benzodiazepine.  When asked to measure "after-images" using a light device, the patients' scores were similar to the control subjects whereas before, they were much longer lasting. 

--Brain mapping studies of people with HPPD show a clear difference in temporal lobe activity as compared to controls.

*(Patients on clozapine must have a weekly blood test to monitor for the loss of white blood cells, called "agranulocytosis." This is a rare but potentially dangerous side effect, one that requires an immediate end to clozapine treatment.)

*(e.g. "Tardive Dyskinesia"--characterized by repetitive, involuntary, purposeless movements. Features of the disorder may include grimacing, tongue protrusion, lip smacking, puckering and pursing, and rapid eye blinking. Rapid movements of the arms, legs, and trunk may also occur.)