Adrenergic agonists are classified based on their mechanism of action. Additionally, sympathomimetics can also be categorized by their therapeutic actions. Pressor agents, or vasopressors, are used to elevate low blood pressure. These include endogenous catecholamines, such as noradrenaline, and synthetic agents like phenylephrine. They also serve as cardiac stimulants by increasing the heart rate, the force of contractility, and conduction velocity. Bronchodilators include β2-agonists such as salbutamol and terbutaline. They relax lung muscles and widen the airways, making breathing easier. α-agonists like oxymetazoline and phenylephrine act as decongestants. They help relieve nasal congestion and clear blocked noses. Noncatecholamine sympathomimetics, such as amphetamine, act as CNS stimulants. They induce restlessness, euphoria, and insomnia through the release of DA and serotonin. β2-agonists like ritodrine are used to relax the uterus and delay premature labor.