The medications of choice for acute asthma attacks are short-acting beta2 agonists, and commonly used medications include albuterol and terbutaline. An acute asthma attack is defined as the sudden onset or worsening of symptoms such as wheezing, shortness of breath, chest tightness, or coughing, accompanied by a decrease in expiratory flow, and is often caused by exposure to an irritant such as an allergen, or by inadequate treatment. The drugs of choice for acute attacks are short-acting β2 agonists, which relieve asthma symptoms by agonizing the β2 receptors in the airways and rapidly relieving bronchospasm. There are three kinds of preparations: inhalation, oral and intravenous, and inhalation is preferred. Commonly used drugs include salbutamol and terbutaline. Short-acting β2 agonists should be used intermittently as needed, and should not be used chronically or singly. Major adverse reactions include palpitations, skeletal muscle tremor, and hypokalemia. Patients with asthma should carry emergency medication with them as prescribed by the doctor and should not self-medicate.