The Drug Enforcement Administration recently issued a report stating that trafficking and abuse of prescription drugs such as Oxycontin, Oxycodone and Hydrocodone are much more widespread than previously thought and that they even rival cocaine and heroin as a social and law enforcement problem.
As the population ages, the amount of prescribed medicine in circulation has risen, and therefore become more available to people seeking to abuse it. Those who are taking medicine not prescribed to them, however, usually have no idea as to safe dosages, and there have been a large number of overdoses in the last few years, as well as drug interactions and side effects that the abuser was not prepared for. Prescription narcotics are addictive, and have all the social costs associated with the more well known illegal narcotics.
Over the counter drugs are abused in a number of ways, from cold medicine to stimulants to pseudoephedrine (Sudafed). Since often times such medicines contain ingredients which help people to sleep, they can be dangerous in large amounts, and often people with no symptoms at all will use them as a cheap high. Sudafed was used until recently as a key ingredient in the manufacture of methamphetamine (now major drug labs in Mexico have put them out of business). The US has responded by putting age limits on some over the counter drugs as well as limits on how much you can buy at one time.