This post is a bit buried, but related.
http://www.bluelight.org/vb/threads/682670-DXM-trip-did-not-happen?highlight=lithium+dxm
He experienced the same as me, a headache and paranoia that we might be beginning Serotonin Syndrome.
Thanks for the good advice,
paranoid android. I wasn't actually aware of Lithium lowering the seizure threshold and that's good to know.
However, I have an unusually high seizure threshold so, for today at least, I will be the guinea-pig. I've just dosed 600MG DXM about an hour ago, in the form of gel-caps, and have decided to skip my 3rd and final dose of Lithium, of the day, despite it staying in your system like an SSRI, I know. I just got paranoid and didn't take it.
Trip-Report Begin: Today, I've taken 300mg Lithium at 10AM and 300mg Lithium at 5PM and a Klonapin at 5PM.
Dose: 500MG - DXM
+1:00 I have an obvious fever and headache, so I took some aspirin and might go take a cold shower in a bit.
Drinking a full glass of water has my stomach killing me and I think I'm about to have some serious... err... Diarrhea.
+1:15 Oh Dear God... I think I'm going to spend the rest of the night in the bathroom. Headache is mostly gone. I think the water actually got rid of the headache, instead of the aspirin.
+1:30 I have no idea why the onset came on so fast, normally it takes like 2 hours for DXM to hit me. I did take a K-pin earlier in the day for my nerves. I am so incredibly dizzy right now, but no euphoria, no CEVs, but it's "bright" when I close my eyes in a normally lit room at 9:20PM [EST].
Time is messed up. My girlfriend just told me that it's been two and a half hours since I dosed.
This is not enjoyable, forgetting all the gastrointestinal issues, the buzz is like a horrible alcohol variant with no stimulating effects or mood upping. I'm just dizzy as heck...
I'll finish this post, while I can and come back and edit later.
Current Conclusion: Lithium prevents all of the desirable effects of DXM, somehow. I'm just sitting here, fumbling around, feeling pretty retarded...
I'm sorry for the absolute lack of useful information.... Other than:
Don't combine Lithium and DXM. Lithium breaks DXM.