"i took two a.m. doses of prescribed 15 mg phentermine over the course of two days. i experienced &quot;amphetamine comedown&quot; symptoms in the evening of both days, including some minor chest pains and pressure, so i decided to discontinue the pills. i then had to endure a 3-day unpleasant amphetamine withdrawal period. from two small doses. i know i am sensitive to drugs, especially &quot;uppers&quot; and &quot;downers&quot; so i suppose that was the reason why this happened to me while attempting phentermine for weight loss. i will never take it again because i did not feel safe while on it. just be careful if you are sensitive to substances. ask for the 8 mg dose to start and know that the drug puts a strain on your cardiovascular system."