Strong pain is a survival responce which will not be needed in future times. However, a feeling of touch is necessary (for example, see people who have no pain responce, who may try things like walking on a broken leg simply because they do not know it is damaged). Because of this, transhuman bodies will need some way of regulating pain. Once we have a more complete understanding of the human brain, technology may allow us to supress pain signals. This may lead to the fact that once humans are taken off the "drug", they will feel a lot of feeling that they did not have, therefore torturing them. Once everyone is on it, if it gets recalled for a reason (addictiveness), they will stay on the "drug". Companies will not be able to resist the oppurtinity to use additives to the "drug", for example mind control. The government will be controled by the drug, as they cannot get off it without feeling immense pain. This will lead to a dystopian world.