For some yes, but before giving you specific examples it may be useful to outline how drugs (or more generally, what we call controlled substances) are classified. According to the law we recognize five different drug categories, or schedules, which determine whether or not it is legal to use a drug and under what circumstances.
- Schedule I includes drugs with high abuse potential but no currently accepted medical applications, therefore no prescription can be written for any Schedule I substance. Some of the drugs in this category are heroin, GHB, ecstasy, LSD, and cannabis (i.e. marijuana).
- In contrast, Schedule II drugs also have high potential for abuse but have, in addition, accepted and approved medical applications. In this class, we can find various stimulants (e.g., cocaine, amphetamines), opiates (opium, methadone, oxycodone), and dronabinol (Marinol), which contain the main active ingredient in marijuana (THC).
- Schedule III drugs, like anabolic steroids, buprenorphine, hydrocodone, and ketamine, have in general less abuse potential than Schedule I or II drugs and have accepted medical uses.
- Schedule IV (e.g., benzodiazepines and barbiturates) and Schedule V (e.g., cough suppressants containing small amounts of codeine) drugs, have decreasingly lower potential for abuse than Schedule III drugs and also well accepted medical uses.
As you can see, dividing drugs based on their legal status is not very helpful in answering your question: indeed, there are legal substances that can be abused but have no approved medical use (e.g., tobacco, alcohol) while, conversely, many substances that are illegal under certain circumstances do offer medical benefits when used properly and under the supervision of a physician. Opiates, for example include both morphine and other pain relievers, and are used by physicians to provide pain relief to millions of people. Also, amphetamine (speed) and methylphenidate are legitimate treatments for Attention Deficit Hyperactivity Disorder (ADHD). Doctors who prescribe these drugs are well trained to evaluate if and when a person needs them, and how much is safe for a specific person to take. Prescription medications, when properly used, are of invaluable help in the treatment of serious medical conditions, but their use becomes dangerous and illegal when not under the supervision of a physician--even if they are taken for their intended purposes--to relieve pain, increase attention, or lose weight. Of course their abuse to get high, to improve mental or physical performance is also dangerous and illegal.