An uncommon clinical use of stimulants like amphetamines and methylphenidate (or cocaine?) is to treat the somnolescent side effects of high dose opiods. The stimulants can increase cognitive function and awareness in people who take opiods even if they do not have ADHD. This can allow for a pain patient to increase their dose of opiates to better treat pain symptoms. In recreational drug users this combination may not result in the euphoria experienced with the separate drugs. However, this could be a way for any patients with untreated pain, and or side effects from their treatment to improve their quality of life. Consequentially, a patient who is a recreational drug user, and is prescribed pain meds may have a reasonable way to be given more pills, plus a source new substances. Not that anyone would want more pills.
A source for this is here
http://www.sciencedirect.com/science...7945ba52a0f304
In the same issue there is also an article about a study on rats which concludes that potentiation of opiods (morphine) with amphetamines amd methylphenidate merits more study.