In my personal experience definately. There was a several month window of time quite a few years ago which i dosed DXM every single day at the 1p level occasional 2p, and there was a definate progression of tolerance. By the time I decided i was done my dose had become significantly higher than when i began, and in fact i found the dose i had started on towards the latter part produced a minimal effect if any. The increased dose at that point was only there to achieve the same level as when I began not due to any effort to take it any further than where i started. Although i find this interesting and possibly indicative that i have a unique metabolism tangent from the average, and this is just from memory and may not be correct either, but i seem to recall that DXM is usually present in the body beyond 24h later usually resulting in increased effects when dosing again the next day. If any of this is incorrect please comment as such, but regardless i never expirienced anything like this