There have been many instances of Xanax being used as a "date rape drug", due to the sudden onset of the medication and the side effect of memory loss.
One of the reasons it is so hard to stop taking Vicodin is because of the intense withdrawal symptoms that occur as a result of abrupt cessation of use.
Valium can cause anterograde amnesia (an inability to recall the recent past), which may persist as long as 6 months and may not ever fully return to normal after an individual stops taking the drug.
Physical dependence and withdrawal symptoms are known to develop after only five days of the administration of Morphine.