From what I've learned, Phentermine is not an alternative but Adipex is actually the most popular brand of phentermine diet pills. It is manufactured by Teva Pharmaceuticals USA, and considered as high quality, hence it does not come cheap.
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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.
Phentermine comes in different brands, and to learn more about these please visit Link hidden: Login to view
Hope this helps.