• Phendimetrazine is a drug that stimulates the nervous system. It is composed of the same chemicals as amphetamines and it causes similar physical effects such as rapid heartbeat, decreased appetite and increased blood pressure, according to Theathlete.org. Phendimetrazine is prescribed on a short-term basis to people who are obese and seek to lose weight. The drug should not be taken without a doctor's supervision as there are long-term risks associated with it, especially when it is consumed in high dosages or for extended periods of time.
  
  

Tolerance

• When Phendimetrazine is used for a long period of time, your body can become tolerant to the drug and it may no longer be effective. To continue to experience the proper effects of Phendimetrazine, you may need to take a break from it or have your dosage increased.
  
  

Dependence/Addiction

• After taking Phendimetrazine in increased dosages for extended periods of time, you may become dependent on the drug and feel as though you can not do without it. You may also feel that you need to continue to increase your dosage to get a desired effect. When these feelings occur, this may be a sign that you have become addicted to the drug.
  
  

Withdrawal

• If you suddenly stop taking Phendimetrazine after using it for a long period of time, you may experience withdrawal symptoms such as depression, nausea or vomiting, stomach cramps, trembling, weakness and extreme fatigue.