If your found to have amphetamine in your system can you say its from phentermine and show 2 year old prescription?

Ha! No. First thing is that they are two different medications and have no similarities at all. One is a stimulant (amphetamine) and the other is an appetite suppressant (phentermines). Phentermines have a maximum half life of 36 hours. Take your prescription dosage and do the math. It depends on your prescription but the longest a phentermine would stay in your system would be three weeks.

Also, since you are posting this question, you are obviously worried about amphetamines showing up on a drug test. Amphetamine has a half life of about 10 hours. If you take 60mg of, let's say, Adderall on Monday. Any measurable amount of the medication would be out of your system by Friday.

updated

Well i was told that phentermine would show up during a drug test as a amphetamine, that's whats got me scared. About 2 or 3 days before the test i started taking my old prescription (2 years old) of phetermine again. I even took one the morning of the test because i didnt know it would hurt anything. So now im just scared. I need a job so bad.