You are not alone here because quite a number of people are undergoing the same thing. phentermine without prescription tolerance has frustrated most of us. Some of us experience a diminishing in appetite suppression a few weeks after commencing the treatment while others are able to enjoy this for a longer period. This is the reason why I have decided to step forward and help others over this issue.Phentermine, like any other drug works with neurotransmitters in one’s brain. Its main purpose is to ensure that the neuron bundles release a certain group of neurotransmitters commonly called catecholamine and they include; dopamine, epinephrine and norepinephrine. Their main duty is to signal a fight response in your body which helps in putting a hunger halt into your body. The reason as to why you lose your appetite is because you brain does not receive hunger messages. This may be due to the effects of phentermine leptin levels in the brain. Satiety in this case can be signaled via the presence of leptin. It is also believed that the presence of increase in the level of catecholamine is in a way responsible for halting neuropeptide Y, which is another chemical messenger. This is the chemical that is responsible for initiating a decrease in eating, energy use and increased fat storage.