I am going to keep this as brief and to the point as possible.
I have had this disorder for 18 years. I have tried at least forty medications and I had very limited success in treating it with Clonidine and Klonopin. However, the "progress" I had with these medications was a bit like throwing a blanket over a fire siren; they muffled the noise but, the siren was still blaring. The medications I am currently taking cut off the sound to the siren and I know you HPPDers understand that distinction.
About 5 months ago I began Keppra. This medication can make you very drowsy and Keppra rage is very real. I kept the dose low, quartering a 200 mg tablet, so just 50 mg. If I upped the dose the side effects would become too great, so I just maintained the levels without any side effects. Slowly, day by day and week by week, I noticed real progress in the way I was feeling but, more importantly in the way I was thinking (I will say more on that at the end). If I had to quantify, I would say low dose Keppra reduced my symptoms between 40-60% on its own.
After about 4 months my reduction of symptoms inspired me enough to believe that this may not be impossible to pharmaceutically treat, despite past failures with antidepressants, antipsychotics, mood stabilizers, beta blockers, benzos and other atypical meds such as, Sinemet, unfortunately.
I began to think about the fact that LSD after ingested begins by agonizing the 5-HT2a receptor, which then agonizes NMDA receptors, which is thought to largely account for the perceptional changes. Then the path gets murky, but I wondered if in the case of HPPD excitotoxicity occurred at some point (NMDA receptor overload) which works by overloading calcium channels.
5-HT2a------->NMDA---------->excitotoxicity (calcium ions)
I wondered if somehow in the case of HPPD if this cycle was still going on and if trying to block it at one of those receptors might help. I began with a 5-HT2a antagonist, Pizotifen and it had no effect. I then moved on to an NMDA antagonist, Namenda, which helped a little to calm me down, but ultimately did not move the needle. Then I read Ghormeh's post on this web site about visual symptoms being reduced by a calcium channel blocker called flunarizine and gave it go.
It didn't take long at all to get a drastic improvement with this. My typical days now consist of a 70-95% reduction of symptoms. There are many times during the day when I feel completely normal for long periods of time. My generalized anxiety is almost entirely gone, my thinking is abundantly more linear and the visuals have improved (especially light trails in the dark, less so visual snow, but still received some decent benefits in this department). I believe the meds are working synergistically. Keppra, among others things, suppresses activity in the amygalda, which is the primary fear center of the brain and a speculated source of PTSD. Flunarizine prevents excitotoxicity and has been shown repeatedly to block the effects of MDMA in the lab. It is a logical pairing. But regardless of how it works, it is working and working very well.
I ran an experiment on the flunarizine which tells me that is without question directly helping my HPPD. For the last 18 years if I were to wake up in the middle of the night and move something like my cell phone or alarm clock in the dark I would get a light trail. I noticed that they had stopped when I began the flunarizine. I went into a dark room and spun around my powered on cell and there were no trails. Two days later I stopped the flunarize and ran the test again 48 hours later and the trails came back.
I haven't felt this good since before "the incident". On the change in thought patterns I mentioned early; I believe HPPD is a perceptional and thought filtering problem. These medications allowed me to restore thought filters (and a good deal of the perceptional ones related to how you perceive the feeling in and of your body). My mind is segmented again, instead of jumbled. There are thought patterns I know to follow in everyday life and thought patterns I know to avoid. Before when HPPD was in control of my life I could hypothetically understand this, but I couldn't apply it. Now I can apply it very easily.
I hope this information helps. On Keppra, there are a few posts on this forum that state that you need to get up to 1500 mg in order for it to work and a few people advocating against a set dose and for whatever you body calls for. Obviously I would like to strongly echo the latter sentiments. For those of you that tried Keppra and couldn't handle it due to the side effects I would suggest you may want to try it again at a low dose. I am a very strong believer that if something works for one of us, it will work to a good degree for all of us because there must be biochemical uniformity to this problem. On flunarizine, I take 1mg at night. This is a strong medication so if you try it ease in with the lowest dose possible.
I have been on this pair now for a few months. I wanted to make sure my reduction of symptoms remained before I posted. They have been getting better. Things aren't perfect always, but I have regained the vast majority of my former self. Do you remember how you use to feel during a spring day walking around outside or flopping down on your back in the grass and looking up at the sky? Being able to process the sensations of the cool air and the heat of the sun and the moving trees in the wind all at once and then getting that feeling of being a part of everything around you? It gave me that back. I had to work at it though. The medications seemed to help me in part by allowing me to help myself to put my thoughts back together in an orderly fashion.
Below I have made a list of what has improved and how much:
Generalized Anxiety-85% improved
The feeling of feeling that you are one with your body-80% improved
Visual Snow-20% improved
Linear Thinking- 85% improvement