Biovail
Bluelighter
What extra dimensions do you mean? I can create a manifold with as many complex extra dimensions as I damn well want/need to. It's no biggie...I mean look at Bosonic String theory, it works in 24 dimensions.(Regular old quantum field theory works in a function space with dimension infinity!) Plus we use all sorts of extra dimensional measures (above those of the 3 spatial and 1 temporal) every day.In that for e.g. if I say "It pays $15.00" The quantity $15.00 is not a dimensionless quantity. It is a measure in the dimension "money" That is, I can not be $15.00 tall, or have $15.00 density. Additional "proof" of it being dimensional is it readily able to be worked with via dimensional analysis.
If I have $15.00 AND I've worked for 1 hour, I am getting $15.00/hr. Remembering time is also a dimension, we conclude that dimensional analysis does in fact apply to IRL, and that IRL we make use of extra dimensions on regular basis.
tl;dr we don't need drugs to be aware of so called extra dimensions.
Would you disagree that drugs are useful for putting previously understood concepts (or even those not well understood) in a new context and for gaining an alternate perspective on them?
The human mind is very odd. Once a person thinks they have an understand of something, it can be very difficult to change that opinion or alter their understanding. Take for example the common old woman/young woman optical illusion:

Once you have the image of the young woman in your mind, it can be difficult to alter your perspective in order to see the old woman. I would argue the same concept applies to generalized thinking. Drugs might not literally enable you to perceive additional dimensions, but they may allow you to think about them in ways you didn't previously consider meaningful.