subject: Phentermine alternative [print this page] Although Phentermine has positive impact in reducing weight but it is only prescribed on the advice of the doctor as it has side effects too. Some of the patients are facing severe complications due to various reasons such as not carrying out regular exercises, improper diet plans, not referring to the doctor or not following the correct prescription, taking Phentermine drug during late night or missing out the regular doses and taking double doses of Phentermine drug. The major drawback of this drug is its addiction. If patient is not taking the proper dosage it can damage the lungs that can cause death. But by taking precautions you can avoid further complications.