Phentermine is a meds used to speed weight loss in overweight people .It is used together with diet and exercise to treat obesity ,especially with the people who are in high blood pressure , high cholesterol or diabetes.Phentermine is an indirect-acting sympathomimetic agent that acts by releasing noradrenaline from the presynaptic vesicles in the lateral hypothalamus. This increase in noradrenaline concentration in the synaptic cleft results in the stimulation of beta2-adrenergic receptors.