Adipex is classed as a controlled substance with the US and is only available on prescription.
The chemical composition of Adipex is similar to that of amphetamines and if taken for a prolonged period of time can be addictive. It is usually recommended that Adipex be taken for no longer than a period of a few weeks without a break.
Adipex can also be habit forming and it should only be taken by the patient it was prescribed for.