Nothing could be further from the truth. There are both federal and state laws that make using or sharing prescription drugs against the law. If you take a pill that was prescribed to someone else or give that pill to another person, it is not only harmful, it is illegal.
Federal and State Drug LawsPrescription drugs are considered "controlled substances." The federal Food, Drug, and Cosmetic Act makes it clear that the only legal way to access prescription drugs is to have a doctor's prescription. An excerpt:
...No controlled substance in schedule II, which is a prescription drug as determined under the Federal Food, Drug, and Cosmetic Act (21 U.S.C. 301 et seq.), may be dispensed without the written prescription of a practitioner.
Even Doctors Can Break the LawSometimes even when a doctor does prescribe a drug, it is illegal to do so. For example, if a doctor writes a prescription for too many pills - either knowing that they are going to be resold or knowing that the amount is way too much medication for a single patient - that too can be a crime.
That's why the doctors who prescribed drugs for Anna Nicole Smith face criminal charges for conspiring to illegally provide drugs to someone they knew was an addict. Smith died as a result of having a combination of different drugs in her system.
Possession With Intent to DistributeSome states have laws making it illegal for you to be in possession of your own prescription drugs under certain circumstances. Most states have laws that make it illegal to carry around pills that are not in their labeled prescription bottle.
In other words, if you are carrying around pills that your doctor prescribed to you, but you have them loose in your pocket or purse, that is illegal. The presumption is that you are carrying them in that manner so that you can distribute them.
Just As Illegal As WeedNo matter what your middle school or high school friends tell you, using and sharing prescription drugs is just as illegal as possession of marijuana. There is a good reason for it - taking drugs not prescribed for you is very dangerous.
Not only can taking prescription medications make you very sick, it can land you in jail. Just because you got them out of your mom's medicine cabinet doesn't make them legal.
More Information: Myths About Teen Prescription Drug Abuse
National Council on Patient Information and Education, "Myth Busters: 6 Myths about Teens and Prescription Drug Abuse (PDF)." November 2009
U.S. Drug Enforcement Administration. "Federal Food, Drug, and Cosmetic Act, Title 21, Chapter 13." Jan. 22, 2002.