A few people have independently contacted me about an additional plateau -- one reached not by increasing the dosage but by prolonging the experience. I searched for some time for a name before settling on "Plateau Sigma", both because it seems to be related to sigma activity (see Section 10.2) and because it occurs as one sums up small doses (sigma being the mathematical symbol for summation). This summation may lead to a strong potentiation of the psychotomimetic effects of DXM (227). Over half the people who had a Plateau Sigma experience have said it was extremely unpleasant and that they would never repeat it.
The most commonly reported dosage regimen for Plateau Sigma is given below. However, before giving it, I warn you strongly against making this sort of attempt. DXM at high dosages is probably hard both on the brain and the body, and extending the experience is likely to increase the chance for dangerous side effects. Furthermore, one must be experienced enough with DXM, with the psychedelic experience in general, and with one's own mind, to be able to understand the experience. Everyone who has reported a successful experience with this dosage regimen has been at least 23 years of age. While I do not doubt that some younger people may be capable of having a good experience at this plateau, most seem to be unable to understand it and unable to control it, and there may be a real danger of psychotic breaks. Finally, the experience is in some ways acutely uncomfortable, as one's contact with inner and outer reality seems to break down entirely.
Combining suggestions from others I have come up with the following dosage regimen. Start relatively early in the day (the experience degrades if one is too fatigued), at about 6 to 10 hours after awakening. It helps tremendously if one is in good physical shape and not under emotional stress. Take a low second plateau dose. In three hours (or about 1 hour after the peak), take a second low plateau dose. At three more hours (or, again, 1 hour after second peak) take a high second plateau or low third plateau dose. After coming down from the third plateau, instead of going back to the second plateau and down to baseline, you may be left in Plateau Sigma. Drugs which inhibit cytochrome P450-2D6 seem to enhance the duration and intensity of the experience. Nicotine is reported to inhibit it, and may even prevent it entirely.
At Plateau Sigma interesting things happen to reality. Some have reported vivid, entirely realistic contacts with alien entities, spirits, gods and goddesses. Unlike the fourth plateau, these contacts often take place with eyes open, immersed in everyday reality. Although none of the people who reported these experiences to me had bad trips, most related that the experiences were so real that they felt they easily could have.
Vision suffers a curious change, seeming to consist of well-processed but highly strobed images; so strong is the effect that it seems as if one is looking at the world under a fast strobe light. The eyes don't seem to track in synch with the inner 3D model of the world, so that when one looks to one side or another, the world lurches back and forth for a moment. Interestingly, it almost seems as if one is looking at the world from an inner vision with the eyes closed (see Section 5.11).
Finally, thoughts can be totally deranged. Connections between entirely unrelated ideas form, causality goes out to lunch, and one's personality seems pretty much dissolved into the universe. Expect to hear a lot of voices; some people find themselves totally obedient to them. There seems to be a "tireless" quality to the experience, as if one does not feel either fatigue or emotion directly, but only receives information from the inner voices ("sit down now, you're tired"). There are interesting comparisons both to accounts of acute schizophrenia and to Jaynes' postulated bicameral mind (350).
Again, let me warn you of the dangers here. You are probably stepping head first into psychosis, and unless you've got a very good trip sitter, you might end up coming back to reality in a padded room. Or, if you're really unlucky, you might freak out, have a hypertensive crisis, and end up in the hospital. Chronic high-dose use of PCP has been implicated both in deterioration of some brain areas and in cerebral hemorrhages. While PCP stands som!ewhat alone among dissociatives due to its additional and peculiar pharmacology, one should always be cautious when blazing trails in uncharted territory.
One last time: Be Careful!!
